Home

User manual ()

1. 020001 could process One or more input bytes have been lost 0x0002 Internal system error System got into a state which should not be possible This error should never appear Except for me when I am writing new SW 0x0003 Mode command value error You specified a non existing mode 0x0004 0 DC motor frequency error Motor was not in DC mode You tried to set a x0005 D brushed frequency on a motor which was off or was specified as a stepper motor 0 Duty cycle error Motor was not in DC mode You tried to set a duty cycle x0006 i frequency on a motor which was off or was specified as a stepper motor 0x0007 Illegal frequency given in set brushed frequency command The frequency you specified was out of range 10Hz 30KHz 0x0008 Illegal duty cycle given in set brushed duty cycle command The duty cycle you specified was out of range 0 1000 0x0009 No brushed frequency set You gave a start command to a brushed motor but the frequency was never set 0 No stepper frequency set x000A You gave a start command to a stepper motor but the frequency was never set 0x000B Stepper motor command given to none step channel You gave a step command to a motor which was off or in brushed mode 0x000C Not in stepper mode You send a set stepper freq command to a motor which was not in stepper mode Ox000D 0x000E 0x000F 0x0010 Start command given with halt active You tried to start a motor but the halt line is activ
2. 16 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 connections You can use a different voltage for VAB as for VCD but all grounds of the board are connected together Again at the bottom of the board you find a diagram which shows the power connections connected to a battery symbol If you have a motor for a voltage less than 8volts you can try to connect it using a series power resistor This will work for stepper as well as brushed motors 2 42 5 Connecting end stops To connect end stops you have to add a contact between one of the EXT pins and ground You can use a mechanical switch or an optical switch As each EXT pins has a pull up resistor of 4700 Ohms to the controller s 3 3 volt supply you only need to connect a switch between the pin and ground These are the J3 pins which can be programmed as end stop 4244557713 JS GEDIR M Ez Gertbot end stop pins Looking at the pins above the end stops are assigned as follows Motor 3 B Motor 2 B Motor 1 B Motor 0 B Motor 3 A Motor 2 A Motor 1 A Motor 0 A As stated all you need is a switch from the pin to ground The following diagram shows how to connect all four B end stop switches YS A v TAM 8 8 055407 Nd i PIRANO WS ye a pursur AM um gt You can connect a switch which is normally open and gets closed if the end stop position is
3. Gertbot Rev 2 3 September 2014 0 Iwantto use it NOW If you are like a lot of engineers you don t want to read a manual you want to get started NOW I can t recommend that but this chapter might limit the damage if you still want to do so Please use the following steps l Connect a DC brushed motor or stepper motor to the Gertbot Also connect a power supply for your motors to the Gertbot See 2 Connecting things up for how to do that From here the instructions assumes you have connected a DC motor to contacts A1 A2 or a stepper motor to contacts A1 A2 B1 B2 Plug the Gertbot board on top of a Raspberry Pi board which is powered down Then boot the device On a B make sure to plug the board on GPIO pins 1 26 Login and download the software git clone git github com lt TODO gt You might want to make a directory to put all the Gertbot data into If you have not started the X windows system yet do so now startx Open a terminal window and go to the directory where you have cloned the Gertbot GUI software Type gertbot That is dot slash gertbot You may get a warning that your UART is not available If so follow the instructions to enable the UART After that you see this zi Connect SEEM TTET TEAN Ir Fr lr Sort JT Poe T 19 Sr Snn Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 EE gertbot The Com
4. The 5V output of the cable can power the Gertbot so no external 5V supply is required Rx is the external computer receive it is the Gertbot transmit Tx is the external computer transmit it is the Gertbot receive 2 6 22 7 2 Connect to J6 Pi connector You will need minimal a 10 pin male header organised as two rows of 5 pins 0 1 pin pitch Maximum you can use a 26 pin male header organised as two rows of 13 pins 0 1 pin pitch Connect the signals as follows Signal Pin Pin type on Gertbot Ground 6 Ground 5Volt 65mA 2 and or 4 Power Transmit 8 Input Receive 10 Output Attention Optional 22 Output Transmit is the transmit pin of your external computer It is a receive pin of the Gertbot Receive is the receive pin of your external computer It is a transmit pin of the Gertbot Not picture is available of this 2 6 32 7 3 Connect to J14 Not mounted For this you will need to solder a connector on the Gertbot You will need a 5 pin male header organised as one row of 5 pins 0 1 pin pitch Connect the signals as follows 20 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Transmit is the transmit pin of your external computer It is a receive pin of the Gertbot Receive is the receive pin of your external computer It is a transmit pin of the Gertbot Below is a picture of a FTDI USB to TTL cable connected to J14 The 5V output of th
5. This means there is the probability that the pulse width will be slightly longer This will happen if a stepper timer interrupt arrives and at the same time the CPU is busy with a different interrupt routine or is running a critical section If the other channels are NOT working in DCC mode measurements have shown the jitter to be smaller than 5p seconds DCC mode When operating a channel in DCC mode the jitter on the other channel operating in stepper mode will increase There is no hard figure also as the more channels operate in DCC mode the larger the jitter will be If very accurate stepper times are required and DCC mode at the same time there are two solutions 1 Keep the stepper frequency low so the relative error is not too big 2 Purchase an additional Gertbot board Run the DCC mode on one and the stepper modes on the other 6 3 2 Accuracy The stepper motor frequency has been given a very wide range This is so some applications can run their stepper motors at 5KHz whilst others e g who want to debug want to run them at 0 25 Hz 1 step every 43 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 4 seconds Therefore the step frequency is made a 24 bit parameter The smallest possible step frequency is 1 16 Hz One step every 16 seconds The maximum is 5 KHz 5000 steps sec The frequency is implemented in three ranges and in each range the accuracy
6. cascade Pi C1 C2 D1 D2 2xDAC OARS 10xl O The four H bridges can be used to control either four brushed motors or two stepper motors or two brushed and one stepper motor You talk to the board using the UART serial port which must be set to 577600 baud 8 bits 1 start 1 stop bit no parity The Gertbot is controlled by sending commands over the UART port There are commands to select what type of motors you have brushed or stepper or a mixture There are commands to run your motors to specify when they should stop to control the relays read the ADC set the DAC and a lot more There is an expansion connector which allows you to connect up to four Gertbot boards in parallel This gives you control over maximum 8 stepper motors or 16 brushed motors or various mixtures of both 1 1 LEDs The board has four LEDs labeled as D5 D6 D7 and D8 At the moment only three of those are used D8 Heartbeat Slowly blinking Indicates the main system loop is running D7 Error Fast blinking Indicates there are errors in the error queue Reading the errors from the queue using the read error command will stop the blinking D6 Halt Steady on Indicates the HALT line is active D5 Currently unused 13 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 2 Connecting things up 2 Connecting Gertbot to a Raspberry P
7. 10 5 256 22688 0x00 0x0A 0x80 571 7 Hz 571 7 256 146355 0x02 0x3B OxB3 1500Hz 1500 256 2384000 z0x05 0xDC 0x00 For more details about setting or changing the frequency see 5 3 Frequency 4 114 10 Stop all 0xA0 0x0A Ox0A 0x50 This command stops all motors on all boards In contrast to an emergency stop all the stepper motors will remain powered 4424 11 Switch open drain 0xA0 OxOB id on off 0x50 This command activates or de activates one of the open drain outputs on a board As there are only two open drain per board the valid id values are 0 1 4 5 8 9 12 13 The on off byte can be 0x00 open drain off or 0x01 open drain on Due to the nature of an open drain output off means no current and the open drain output is high 4 434 12 Set DAC 0xA0 0x0C id gt MS gt lt LS gt 0x50 This command writes a value to the on board DAC converter As there are only two DACs per board the valid id values are 0 1 4 5 8 9 12 13 The current DAC is 12 bits Therefore the upper 4 bits of the 16 bit value are ignored Warning the board uses the Digital to Analog converter inside the Atmel SAM32 chip However these 12 bit DAC s do not have the full 3 3V voltage range The range is from maximum 2 75 volts to a minimum of 0 66 volts 4144 13 Read ADC OxA0 0x0C id gt MS gt lt LS gt 0x50 0x50 0x50 0x50 This command reads a value from the on board ADC converter The returned value is unsigned As the current ADC
8. 256 bytes DCC message length error You specified a DCC message length 2 or 5 0x0020 51 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 9 Software The Gertbot comes with a bundle of software All code is available in source code and is licensed under GPL v3 All software in source code and executable can be downloaded from www gertbot com The software consists of 9 1 Gertbot Gui A Graphical User Interface to control the board read the status and generate commands The Gertbot GUI is available in source code and the project file can generate makefiles for Linux and Windows 9 2 Gertbot C drivers C code which allows your C or C program to interface with the Gertbot For a good understanding you should have a browse through this manual A simple example for a two wheeled vehicle is available in the srover directory A more complex example with per wheel speed control is in the rover directory 9 3 Gertbot Python drivers A python module which allows your python program to interface with the Gertbot For a good understanding you should have a browse through this manual A simple example for a two wheeled vehicle is available in the prover directory 9 4 Gertbot DCC GUI A Graphical User Interface to control models trains It is set up to control three trains some points and some signals 52 Co
9. 3 September 2014 repeat is the number of times a command is repeated Values under 4 are not recommended whilst very high values reduce the data rate Range is 4 255 lt preamble gt is the number of preamble bits number of high bits at the start of each packet This value must be gt 14 Range 0 255 DC this is used to generate a DC offset on the output This is not fully implemented yet Beware that not all DCC decoder can cope with DC level produced in this way flags At the moment only the LS bit is used and then only for software debug If the LS bit is set the system will no longer send idle packets when there is no data It will still send one idle packet after each command to guarantee the 5ms distance between commands for the same destination rule 5 3 Connecting it up To connect up a DCC system to a railway use the same diagram as connecting brushed motors Instead of a motor use the two connections of your railroad track The DCC system is polarity agnostic That is it does not matter to which rail you connect the Al or A2 wires For the power you can should use an external 15V DC supply As with the other motors you can use a different supply for the two output Ga Apert 2014 1 groups Eu RB Higher current For DCC mode you can also achieve a higher current output then 2 5Amps For this you must connect multiple output channels in parallel Follow the connection scheme as described for brushed mot
10. Brushed Pulse Width Modulation Motor Frequency and 4 5 Brushed Motor Duty Cycle Mode 9 This mode is under development Mode 9 operates the output in DCC mode DCC stands for Digital Command Control A method of controlling model railway objects The user can send DCC commands from 2 to 5 bytes to board which will then put them on the output The board will generate the checksum byte and also take care of the repeating of the packet 4 3 End stop amp short hot set up OxA0 0x02 id end stop amp short hot mode 0x50 This command enables or disables the end stop mode of a motor and sets the end stop polarity It also sets the motor short hot response 26 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Endstop Bits 0 1 enable disable each of the two end stops Bits 2 3 set the end stop polarity For more details about end stops see chapter 6 1 End stop Bits 1 0 End stop mode 0 Both off 1 A is on B is off 2 A is off B is on 3 A and B are on End stop enable bits Bits 3 2 End stop mode 0 Both active low 1 A active high B is active low 2 A active low B is active high 3 Both active high End stop polarity bits e Active high mean the motor is stopped if the end stop input is high e Active low mean the motor is stopped if the end stop input is low The enable and polarity bits are send combined in
11. On gt m fai si LE m Resend Pol IV Log sync BoardO system Motor 0 Motor 1 Motor 2 Motor 3 ort z More or more ort More You can now play with the buttons and your motor should take 10 steps InYou can change the beginning Lwould advise you te stop with no power Frequency and Steps values on the stater Usescreen to see what they do 11 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Your stepper motor will have a maximum frequency above which it does not work reliable anymore If lt Formatted Space Before 0 pt After 0 pt Line spacing your stepper motor is rattling or only moves back and forth you have either connected the butten single te de that wires wrong or one of your connections is failing For more information about the Gertbet Gui read the manual Gertbeteui pd Gertbot Gui document 12 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 1 Overview The boards consist of e A Central Processing Unit CPU e Four H bridges each 2 5A e Two open drain outputs e Two Digital to Analog converters in CPU e Four Analog to Digital converters in CPU e 10 general purpose input output ports e AUART connection e A cascade port
12. To prevent this the motor controllers have built in protection diodes 5 That is how the ignition spark in your petrol engine is generated 59 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set
13. before all data is send in binary format Thus a value of 76 decimal is send as Ox4C Ox mean the number is in hexadecimal format Sometimes values are too big to fit in a single byte and instead two or three bytes must be used In all cases the most significant MS value is in the first byte Thus the least significant LS value is in the last byte This is the case for transmitted as well as received data For example to send the value 27616 you have to first translate this to hex OXGBEO and then send it as two bytes 0x6B followed by the byte OxEO If you have to send a big number e g 4705118 you send three bytes 0x47 OxCB OxSE There is one command which takes signed number the step command In that case you must make sure your three bytes are accordingly signed twos complement format See also the examples here 4 8 Stepper motor take steps 3 3 Making commands The commands seem complex and making an error in them is easily done The Gertbot Gui is an alternative of making commands with little effort So easy that these days I rarely refer to the command manual Instead I give the command using the Gui and then copy the hex values from the log window in my program But I still needed the text below to put the correct code in the Gui Explanation of twos complement is outside the scope of this manual Please read up on that 22 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set G
14. bit is set high the ADC channel is enabled If the bit is clear the ADC channel is disabled The LS 2 bits of the DAC byte enable or disable a DAC channel Bit 0 enables disables DACO bit 1 enables disables DACI If the bit is set high the DAC channel is enabled If the bit is clear the DAC channel is disabled All unused bits are reserved for more ADC DAC channels in the future 4 194 18 Board configure OxA0 0x id MS gt lt MM gt lt LS gt 0x50 This commands configures a board for various operating modes Currently there are three board features which can be set e Synchronous mode e Attention signal mode e Channel error mode 4 19 14 18 1 Board Synchronous command mode If bit 0 of the LS byte is set the board works in synchronous command mode For details about the synchronous mode see 5 4 2 Synchronous 36 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 4 19 24 18 2 Attention signal mode Attention is a signal shared between all boards which goes to the Raspberry Pi Or the RTS line of the RS232 A controller can only pull the line low Code Attention signal mode 000 Off High 001 Low as long as a stepper motor is running others reserved for future use As the attention line is shared between all motors it will only go high if nobody pulls it low So for the mode 001 this means the
15. commands 2 e ee ert o N XD rer etr HEU iE 44 6 4 2 Synchrono s commands 1 sic sccavsesscesseasecsncentesdconscesteseseencostsoneestcestecdeeneesnteaurenneenecasce 46 A Moreo EET Tel i aiu 7 2 Oscillation 7 3 Brushed motor start stop 8 Appendix Ai error COGS eee date mar tete ep eee Rer ires erae ea ee ater obe ER nea seda eat 50 EE Dc M aai 52 9 1 Gertbot CUL omen D ARP ee erre A RR ERE EE Reit D iR eet 52 9 2 Gettbot C dri vers coco ee a RU MEO EO D E RR ri nae ees 52 9 3 GertbotPython dHvels coe m epp ee me co ee ie e m o AE e a eias 52 9E sGertbot DEC GUD neto e RW DENEN RE UN OON OW tec rie i 52 10 gt Appendix B Technology n rir rr Rte RUE HE SERR SE desneosescensvdeet condeeueest Coamesaneataewies 53 101I DCVOE PEE 53 102 SAG OMA Se PC 53 10 8 Hzbnidge uu oet ee e Re PES RR TATE DROIT RERO EECORe erba tines 54 10 4 DC Brushed Motor os oie t RR ER EROR EO ROOMS REIR tI MIS REP EM Reg des 55 10 5 Stepper motor 10 5 1 Connections 10 5 2 Mechanics 10 5 3 Rotor hold n eir o n tm ere eb e e n uH PR Ebro Dee 57 IDEO 58 10 6 Switching it oni unite eterne ti rene terr tie I eee bee doa 58 10 6 2 Switching it EC 59 4 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set
16. duty cycle after a frequency change As a consequence the duty cycle can be off the requested value for a few micro seconds after changing the frequency There is currently no way around this 4 6 Start stop Brushed Motor 0xA0 0x06 id mode 0x50 This command starts a brushed motor in either direction or stops it You can start a brushed motor only if e You have set the mode to brushed e You have set a frequency e The HALT line is not active e You have no end stops enabled or the end stop in the direction you are moving is enabled but not active e You have correctly connected power and a brushed motor The direction or stop is set by the LS 4 bits of the command Of the sixteen possible values three are used 0x0 Stop the motor Ox1 Run in the A direction 0x2 Run in the B direction The other values are served for future use To make the motor go into a specific direction one output is set high and the other remains low The following table shows the power on the motor control pins in relation to Run A and Run B Mode Al B1 C1 D1 A2 B2 C2 D2 0x0 Off Low Gnd Low Gnd Ox1 Run A High V motor Low Gnd 0x2 Run B Low Gnd High V motor Brushed meterSoft start stop features To prevent large in rush currents the Gertbot supports soft starting For details about soft staring see 7 3 Brushed motor start There are sixteen soft start ramp up values The Start rampfoll
17. is better than 0 2 the step frequency is send as a 16 8 integer That is you send a 24 bit number The MS 16 bits are the integer part the LS 8 bits are the fractional part In practice this means that you multiply your frequency by 256 before you send it out Thus a frequency of 5KHz is send as 5000 256 1280000 0x138800 1 16 Hz is passed as 0 625 256 16 0x000010 The stepper frequency is better than 0 0246 accurate Also the stepper motors frequencies are all derived from the same master source clock but further work independent This means that you can use the stepper frequencies to replace the Bresenham line drawing algorithm 6 4 Synchronous operation Especially with four boards and 16 motors it can take some time to send commands to all motors Therefore the Gertbot has two ways of starting motors in almost perfect synchronisation 6 4 1 Direct commands Direct commands are specifically added to support systems which produce individual step commands Each command can make a stepper motor take between 1 7 steps in either direction Currently there are two commands 1 OxAI start board 0 gt 2 OxA4 start board 0 start board 1 start board 2 start board 3 Direct commands are special in that they do NOT need a leading OxAO or a trailing 0x50 The start board x command bytes are interpreted different for brushed and stepper motors 44 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as w
18. is only present if you run the gui under windows 6 Press the Connect button A log window will pop up and show the search for boards Default from the factory the board has ID 0 so you should see this Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 On the right hand side is the log windows which we will ignore for now 7 Use the control under Motor 0 to select the operating mode Fer There are 6 modes but for now select DC brushed for a DC or brushed motor seleet Dcesuehed Lar Step Gray Off for a stepper motor select Step Gray Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Board System tor 0 DC brushed Step Gray Step Pulse Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 8 For DC brushed motors you see this I ax Connect Com 15 Read Status Read Error 7 r F ReSend T Poll M Log syne BoardO system r Motor 0 Motor 1 Motor 2 Motor 3 Off X Off X off M High High Hiah Endstoppa F Endstopa Endstop Endstoppg F PF Endstopg F s dstpE F 0 Frequency 0 Frequency o Frequency Connect con 15 7 4 le Les et el Resend Poll IV Log Sync Boa
19. line will go high if all stepper motors have stopped running That is only for motors on those boards which have their attention line mode set to 001 The status of the stepper motors is checked every millisecond Thus there may be a delay of up to 1 millisecond between the last stepper motor stopping and the attention line going low The attention signal operating mode is placed in bits 1 3 of the LS byte For the attention line to work correctly you must first set the mode then start the stepper motors If you set the mode to 1 and the stepper motors are already running the line is not updated 4 19 34 18 3 Stop on error 4 19 44 18 4 Board configure command overview The table below shows where all the board configure bits reside in the three bytes Controls MM byte Controls Controls bit i Error chan D bit 2 Error chan B bit 0 Error chan D bit 1 Error chan A bit 2 Error chan D bit 0 Error chan A bit 1 Error chan C bit 2 Error chan A bit 0 Error chan C bit 1 Attention mode bit 2 Error chan C bit 0 Attention mode bit 1 Error chan B bit 2 Attention mode bit 0 Error chan B bit 1 Sync mode Board configure command table The MS byte of this command is currently unused 4 204 19 Read board status 0xA0 0x03 id MS gt lt MM gt lt LS gt 0x50 0x50 0x50 0x50 0x50 This commands returns some status information of the board The following table shows what the return s
20. magnets are active However if the power is removed from the magnets the rotor can freely turn This means a stepper motor that is halted not running can be stopped in two different states 57 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 e Stopped with magnets off In that case a small external force can change the position of the rotor e Stopped with magnets on In that case the rotor will stay in position and it will take great force to move it out of position 10 6 Inductors The windings of your brushed motor or your stepper motor are inductors You should know a bit about inductors if you want to works with motors 10 6 1 Switching it on First rule of inductors They don t like a change in current So they will fight any increase in current The following might sound strange but as soon as you put a voltage on the coil there will be at the beginning no current No current means no magnetic field and thus your motor will not make any movement After a while a few microseconds to milliseconds the current will start flowing and slowly the magnetic field will increase and the rotor starts moving The following is a diagram plus graph showing what happens if you apply a voltage to a coil 58 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev
21. shaft to free the switch again If you don t need end stops you can disable the function and use the pins as a general purpose I O 6 2 Halt There is a common halt line If that is pulled low every CPU will remove the power from all motors and all activity will stop The halt line is common between all cascaded motor boards The halt line can be pulled low by the user or by the system itself You are only allowed to pull this signal low connect to ground Note that you can not start any motor when the halt line is low The HALT input can be used to implement the big red emergency button 6 3 Frequency settings The stepper motor frequency and the PWM frequency are programmable Especially for the stepper motors it is important that you never get a pulse which is shorter than what the motor can respond to If that happens the actual position of the motor will no longer corresponds to what the computer thinks it is Special attention has been given to the code which sets the frequency so that a step pulse may be slightly longer hanthen the programmed period but it is never shorter There is one exception to this rule on an emergency HALT all power is removed from all motor simultaneously This will cut short any step pulses in progress 6 3 1 Jitter The PWM of the brushed motors is completely done by hardware timers Thus they are very accurate However the stepper motors are controlled by the CPU using interrupts
22. stop ramp time is used when the user gives a motor stop command or when a change in direction is detected Halt ramp The halt ramp time is used when e The stop all command is given e Anend stop is activated Reverse direction If a brushed motor sees a change of direction it will 1 Ramp down until the power is off It will use the Stop ramp time for this 2 Ramp up again using the Start ramp time Even if your brushed motor does not require soft start to begin running you may find that you need it to prevent extreme currents when you try to reverse the motor direction without stopping Beware The soft start sequence is only enabled when you send a motor start command It is not activated on each cycle of the PWM Thus if you set a PWM frequency of 10 Hz a DC brushed motor is started 10 times per second You will get an inrush current ten times a second That is likely to trip the over current protection Using a very low duty cycle frequency with DC motors will cause excessive currents to flow If at the same time the protection is set to ignore errors the controller may become hot 49 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 8 Appendix A error codes Code Error condition Ox0000 There are no errors to report Serial input queue overflow The serial data was coming in faster than the CPU
23. the LS 4 bits of the command The MS bits are reserved for future use Short Hot response Each motor controller has 2 error signals When an error is detected the channel is disabled to prevent damaging the output The error signal is also passed to the microcontroller which can respond to it For more details see 7 Motor error The user can program the following responses e Ignore error The controller takes no further action e Stop channel Stop the channel with the error This is not available for stepper motors e Stop channel pair Stop both channels of the motor controller e Stop board Stop all motor controllers of the board four channels e Stop system Stop all motors on all boards Code Error handling 0000 No error propagation 0001 Stop channels A B C D 0010 Stop channel pair A amp B C amp D 0011 Stop board A D 0100 Stop system A D on all boards others lt Unused gt The error handling bits are placed in bits 4 7 of the byte 27 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Example On board 0 motor 2 set both end stops active low error mode is Stop channel OxAO0 0x02 0x02 0x13 0x50 End stops are very useful to implement basic motor control e g to open a garage door you would activate an end stop switch when the door is full opened and a second switch when it is fully closed N
24. 0 4 164 15 Write I O OxA0 0x0F id MS gt lt MM gt lt LS gt 0x50 This command sets the status of the user pins on the expansion connector To allow space for future boards with more I O the command has 3 bytes but the MS byte is currently unused Write to pins which are NOT defined as output pins are ignored 34 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 LSbyte To bit 7 EXT7 6 EXT6 5 EXTS 4 EXT4 3 EXT3 2 EXT2 1 EXTI 0 EXTO Write output byte association table 4174 16 Set I O OxAO 0x10 id MS gt lt MM gt lt LS gt 0x50 This command sets unused pins on the expansion connector to input or output To allow space for future boards with more I O the command has 3 bytes but the MS byte is currently unused The following table shows which pins on the expansion connect are controller by which bit Controls Controls DACI EXT7 DACO EXT6 ADC3 EXTS ADC2 EXT4 ADCI EXT3 ADCO EXT2 Sparel EXTI SpareO EXTO 7 6 5 4 3 2 1 0 Set I O byte association table Setting a bit to 1 makes the pin an input Setting a bit to 0 makes the pin an output The command has no effect on pins which are assigned a function Thus pins which are set as end stop will remain operating as a digital input pins which are set as ADC will remain operating as analog input and pin
25. 1 to stepper mode These are the currently operating modes 0 Switch motor id off 1 Motor id is operating in brushed mode 2 Motor id is operating in DCC mode Under development 8 Motor id is setup as stepper motor using Gray code The lt id 1 gt is no longer usable 9 Motor id is setup as stepper motor using Pulse code The lt id 1 gt is no longer usable All other values are illegal Stepper power If operating in stepper mode there is an extra power on off bit bit 4 If that is set the stepper motors keep power on their stator when stopper If that bit is clear the stepper motors are powered donw when finsihed stepping In effect this give the following operating modes 0x00 Switch motor id off 0x01 Motor id is operating in brushed mode 0x02 Motor id is operating in DCC mode Under development 0x08 Motor id is setup as stepper motor using Gray code The lt id 1 gt is no longer usable The motor will power off when done 0x09 Motor id is setup as stepper motor using Pulse code The lt id 1 gt is no longer usable The motor will power off when done 0x18 Motor id is setup as stepper motor using Gray code The lt id 1 gt is no longer usable The motor will power off when done 0x19 Motor id is setup as stepper motor using Pulse code The lt id 1 gt is no longer usable The motor will power off when done All other values are illegal If a motor pai
26. 2 3 September 2014 At time t 0 we close the switch The current starts to rise and after a while it gets to its maxim value The time that takes depends on the motor coil In a small coil it can happen in a few microseconds a large coil can take several milliseconds to reach the maximum current In the diagram you will notice a resistor next to the inductor That resistor represents the internal resistance of the inductor The resistance is important as it determines the final current value which will flow A good inductor will have a very low resistance Beware that this effect is totally different from the in rush current The in rush current is caused by a lack of counter magnetic field when the rotor is not yet spinning The in rush current also happens on a different time scale in tens of seconds to seconds not the micro and milliseconds mentioned above 10 6 2 Switching it off First rule of inductors They don t like a change in current This also means that if there is already a current flowing and you try to stop that the inductor will fight that as well One way to fight the current is that the inductor will push back by generating a counter voltage This is where inductors can get very very nasty If you switch the current off the push back voltage of the inductor can become thousands of volts high First it can give you a nasty shock literally Second it can blow up your circuit
27. Gertbot Rev 2 3 September 2014 Gertbot Rev 2 3 8 September2014 The Gertbot is a motor power controller board for the Raspberry Pi The strength of the board is that it has its own CPU which frees up the Raspberry Pi from a lot of intense computations and will take care of all the real time requirements All you have to do is give it high level commands Like Board 2 Motor 1 take 2432 steps at 67 Hz Even giving those commands is done for you using the free GUI which comes with it Hardware features e Four H bridges 8V 30V 2 5A e Bridges can be re configured for 2x 5A or 1x 10A e Two open drain outputs 30V 3A e Power full 64MHZ ARM Cortex M3 processor e RS232 connects direct to the Raspberry Pi or other serial interface e Cascade port to control up to four boards at a time e 20 pin connector programmable for o Automatic motor end stop o Four 12 Bit ADC ports o Two 12 bit DAC ports o 8 16 general purpose I O Software controllable features e Brushed motors o Control direction o Speed control PWM 10Hz 10KHz 0 100 o Soft start 0 1sec 5 seconds prevents in rush current o Stop on switch hit e Stepper motors o Take X steps in either direction o Step speed 0 06 Hz SKHz o Stop on switch hit e Digital Command Control model train control o Can send any DCC command 3 6 bytes o Programmable pre amble length and repeat count e Short circuit or high temperature error detection e On error keep running stop motor st
28. ain is like a switch But you can only switch DC currents and you must connect the plus to the drain pin beeause the switeh is an ODx o NMOSEETODO or OD1 As you can see from the diagram above there is no power available at the output For an open drain output to work the user must provide an external power source The open drain output does nothing more than provide a path with a very low resistance to ground when it is switched on There is no protection on the open drain outputs So the board will get damaged if you exceed the current or voltage specification MOSFETS have the notorious habit of a large capacitive coupling from 18 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 the drain to the gate To prevent capacitive voltage spikes from blowing up the controller there is RC filtering between the gate and the controller However there is no guarantee that it will protect under all circumstances 2 62 7 Connecting to other then Raspberry Pi The Gertbot beard takes it commands in the format offrom a serialstandard UART stream UART stands for Universal Asynchronous Receive Transmit Thus you can control the boards from any equipment which has a UART port This can be an Arduino or a windows PC Beware of the difference between a UART stream and a RS232 stream The UART stream is a protocol RS232 is a physical interface standard Do n
29. at the current is flowing through the motor from A to B This will cause the motor to rotate If we close switch S2 and S4 we get that current is flowing from the to the E Formatted Right 3 51 cm Don t keep with next following the red path in the picture below 54 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 We see that the current is again flowing through the motor but from B to A just the opposite direction than in the previous picture Thus the motor will also rotate in the opposite direction Here are some more possibilities These are what is called braking scenarios The motor is shorted which mean any residual current in there can flow and will cause the motor to brake The Gertbot does not support these two modes There are two more possibilities but those are never used If S1 and S2 are closed or if S4 and S3 are closed In that case the switches form a short circuit from to and unless precautions are taking something will get damaged Note that the original DC voltage of the battery is now changed into an AC voltage on the motor contacts A and B which is twice as high As AC voltages are a lot more dangerous than DC you should not use voltages above 18V 10 4 DC Brushed motor DC motor brushed motor or DC brushed motor are all names of a motor which runs of a DC voltage The more voltage you apply the faster it run
30. byte is the original ID The second byte is 0x06 Bytes three and four are the MS amp LS value of the error code See appendix A for a full list of error codes As the command returns 4 bytes it must be followed by at least 4 bytes of 0x50 4 94 8 Stepper motor take steps OxAO 0x08 id MS gt lt MM gt lt LS gt 0x50 This command specifies how many steps a stepper motor should take The value from the three bytes is a signed value between 8388607 and 8388607 A positive value moves the motor in direction A a negative value towards B You can start a stepper motor only if e You have set the mode to one of the stepping modes e You have set a frequency e The HALT line is not active e You have no end stops enabled or the end stop in the direction you are moving is enabled but not active e You have correctly connected power and a stepper motor Once the number of steps have been taken the motor will stop At that momentthere are two possibilities but the current power will remain on the motor windings holding the rotor anchored through the magnetic force A new take steps command will replace a command in progress A value of 0 will stop the motor at the end of the next step but the current power will remain on the motor holding the rotor anchored There is a second way of stopping a stepper motor using the Stop brushed motor command The difference is that the power is removed from the stepper motor co
31. codes eee dvo eee dre evi rere E coelo 20 2 7 3 Connect to J14 Not mounted 0 c nineT an A TE CAE 20 B Command soea tie sce teg eV e E REEL EE Ete E DE ERA ERE 21 3 1 Identifiet nette eO EO ENERO E PER SR ORE EE IS a TO ear HP 21 MER MC EE 22 3 3 Making commands ade tee C E e o Ped eed E RR E ERO RE ERE ARP ste 22 34 v Command tables hte eee rh e dr D ER EE Re Ne e ER etu dete 23 Ay Command details 42 e SG dv RN EE RITE E s 23 4 1 R ad Version eiecti ERG REDE RERO Meth aah 23 42 Operation mode everest e e OR a n RO E OR Abie ne ea ths 24 4 3 End stop amp short hot set Up i c ee HE HET IRE RR ERE ERA ER 26 4 4 DC Brushed Pulse Width Modulation Motor Frequency sse 28 4 5 Brushed Motor Duty Cycle teo OH ROO EDI E ees 28 4 6 Start Stop Br shed Motorsi n e e e ERO e HR RN Ren RED 29 As Read error status suites o b a RU ERO ORE ON e bed 30 4 8 Stepper motor take steps oe eed e ee eee t ret dean 31 4 9 Stepper Motor Step Frequency o e ee e AERE HEY OG SER EE REDE 32 4 10 Stop ial vcs iecit re eoe em eme e e e n e e a e C A ead 33 4 11 Switch oper drain iicuccocosast c m On RR EGO UE AR HEAT OG HERE ERE 33 4 12 Set DAG cercare et e OU REOR ORE DH e Ree reda 33 449 Read ADG ite eo RO eT BO a e DO E te eed ed ote idee 33 44 Read WO cepe oet e pee e I UC ETC RN A Pec 34 4 5 Write Occit ROO RR RT ED ON URP ROO ORE E s 34 4 16 Set UO i eee e RP Oder eecerin 35 4 I7 Se
32. e Attempt to set too many timer events 0x0011 The program attempted to schedule a timer event but there were none left This error should appear during SW development only Serial output queue overflow The board tried to send a response but the output 0x0012 queue was full Data has been lost This can only happen if you did not send enough end of message bytes 0x0013 Illegal frequency given in set stepper frequency command 0x09 The frequency you specified was out of range 1 16 5000 0x0014 Write to DAC which is disabled 0x0015_ Read from ADC which is disabled 0x0016 Enable ADC illegal mask bits Only bits 0 3 may be set with this HW 0x0017 Enable DAC illegal mask bits Only bits 0 1 may be set with this HW 0x0018 Brushed motor move command but channel was not in brushed mode Illegal command 0x0012 You send a command code which is not supported Ox001A Halt line active 0x001B High current hot error status seen on channel 0 50 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Code Error condition Ox001C High current hot error status seen on channel 1 0x001D_ High current hot error status seen on channel 2 OxOO1E High current hot error status seen on channel 3 OxOO1F DCC message queue overflow You send DCC messages faster than the system could dispatch them The current DC queue can hold
33. e FTDI cable can Rev 2 3 September 2014 Signal Pin Pin type on Gertbot 5Volt 65mA 1 Power Ground 2 Ground Transmit 3 Input Receive 4 Output Attention Optional 5 Output power the Gertbot so no external 5V supply is required 3 Commands All commands are 8 bit bytes and are in binary format not ASCII so you cannot type these values into a terminal program Each command must be preceded by the value 0x AO and closed with the value 0x50 Alternative you can make a file with commands and then send that file to the UART port e g The Gertbot comes with several support programs one of which is a GUI which lets you control your Gertbot boards using only your mouse and allows you to make commands files as mentioned above 3 1 You can control multiple boards each with up to four motors Therefore most commands have an identifier ID byte which tells for which board and for which motor on that board the command is intended As you can cascade a maximum of four boards each with maximum four motors that gives you 4x4 16 potential motors to control Therefore the ID byte can range from 0 to 15 The ID s 0 3 are for the first board 4 7 for the second etc The H bridge outputs are identified on the board using the notion A1 A2 B1 B2 CI C2 D1 D2 See 2 Connecting things up on how to connect your motor to those The following table specifies the relation between the ID and the connections motors it contr
34. e dangerous than DC An AC source below 25 volt RMS 35 V peak peak is deemed to be safe Anything above is dangerous Well you are using a DC power source of 30V so you are safe not NOT The board will take your DC power source and turn it into an AC voltage The output of the motor controllers in stepper mode is an AC signal The peak peak voltage is twice the DC voltage on the input To see how this is possible look at the section which describes the H bridges Thus the 30 volts of DC you put into your motor controller will comes out as 60V peak peak AC on the stepper motor pins Dangerous 53 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 10 3 H bridge Below is a picture of an H bridge It consists of four switches with a middle tap The shape of which is sort of like an H S4 S4 A B A B S3 S3 d ad Plus power rails In reality the switches are made using transistors or FETs but for the explanation how it works switches are easiest to understand The switches are connected to power and ground connections So at the left we add the symbol for a battery and the complete electrical diagram becomes S1 S4 T 2 Uu The two contacts in the middle A and B can be connected up to a DC motor If we close switch S1 and S3 we get that current is flowing from the to the following the red path in the picture below We see th
35. ell as the instruction set Gertbot Rev 2 3 September 2014 This is the command byte interpretation for brushed motors Byte Action MS LS XXXXxx00O Motor 0 stop XXXXxxO1 Motor 0 run direction A xxxxxx10 Motor 0 run direction B xxxxxx11 Motor 0 no change XXXx00xx Motor 1 stop XXXxX01xx Motor 1 run direction A XXXX10xx Motor 1 run direction B xxxxllxx Motor 1 no change xxOOxxxx Motor 2 stop xxO0lxxxx Motor 2 run direction A xx LOXxxx Motor 2 run direction B xxlixxxx Motor 2 no change O0xxxxxx Motor 3 stop OLXxxxxx Motor 3 run direction A lOxxxxxx Motor 3 run direction B lixxxxxx Motor 3 no change Below is the command byte interpretation for stepper motors You can stop a motor keep it unchanged or take between 1 and 7 steps in each direction Copyright O 2014 Fen Logic Ltd 45 The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Byte Action MS LS xxxx0000 Motor 0 1 stop xxxx 1000 Motor 0 1 no change xxxx0SSS Motor 0 1 SSS steps direction A SSS 1 7 xxxx1SSS Motor 0 1 SSS steps direction B SSS 1 7 0000xxxx Motor 2 3 stop 1000xxxx Motor 2 3 no change OSSSxxxx Motor 2 3 SSS steps direction A SSS 1 7 1SSSxxxx Motor 2 3 SSS steps direction B SSS 1 7 If you have a mixture of brushed and stepper motors connected to one board you can mix the co
36. en a large number of steps and want the system to stop send a step value of 0 e A008 00 00 00 00 05 Stop motor on A1 B2 e A008 02 00 00 00 05 Stop motor on C1 D2 The motor will stop but the power will remain on the stator Or you can send a DC stop command e 0xAO 0x06 0x00 0x00 0x50 Stop board 0 motor 0 The motor will stop and the power will be removed from the stator Note Even a motor running at the maximum stepper frequency of 5KHz will need 28 minutes to take 8388607 steps 4404 9 Stepper Motor Step Frequency OxAO 0x08 id MS gt lt MM gt lt LS gt 0x50 This command specifies the step frequency The minimum frequency is 1 16 Hz 1 step every 16 seconds The maximum frequency is 5000 Hz The value passed in the command is the frequency you want multiplied by 256 Thus the minimum value you should send is 0x000010 the maximum value is 0x138800 It is not always possible to set the exact frequency but in all cases the real stepper frequency is better than 0 02 accurate The figures below show how the step frequency is related to the step waveforms step period 1 step freq step p step freq wa LI L4 eol i LF un LIL u LS Step frequency mode 2 32 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 step period 1 step freq A1 C1 A2 C2 B1 D1 B2 D2 Step frequency mode 3 Some examples 10 5 Hz
37. ent and in due time may be damaged B Switch channel off In this mode the processor switches the motor channel off It also posts an error message telling the user which channel saw an error To start the motor again you must re send a motor start command or a step command See 7 Appendix A error codes about error messages 47 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 C Switch pair of channels off In this mode the processor switches the motor channel pair off Thus an error on channel A or C will also stop channel B or D This is most convenient for stepper motors It also posts an error message telling the user which channel saw an error To start the motor again you must re send a motor start command or a step command At the moment the controller will NOT automatically be into this mode if you enable the channels in stepper motor mode This is still open as a future enhancement It is up to the user to set the error code for both channels into paired mode D Switch board off In this mode the processor switches al four channel of the board off It also posts an error message telling the user which channel saw an error See the section about error messages To start the motors again you must re send a motor start command or a step command E Switch all motor controllers off In this mode the processor switches al four channel of t
38. ertbot Rev 2 3 September 2014 3 4 Command table Command Val Parameters Operation mode 0x01 id O off L brushed 2 stepper gray 3 stepper pulse End stop setup 0x02 id Bits 0 1 enable Bits 2 3 polarity Board status 0x03 ID Return status of board DC motor Frequency 0x04 id 2 byte value Range 10 30K DC motor duty Cycle 0x05 id 2 byte value Range 0 1024 for 0 100 Start brushed motor 0x06 id 0 Stop 1 goto A 2 goto B Read error status 0x07 ID Returns 0x07 id 2 byte error code Stepper motor take steps 0x08 id 3 byte signed value 0 stops Step Freq 0x09 id 3 byte value Range 16 128000 Stop all Ox0A 0x81 Stops all motors on all boards Open Drain OxOB id O idle 1 active Set DAC OxOC id 2 byte value Read ADC 0x0D id Returns OxOD id 2 byte error code Read I O OxOE ID 3 bytes Write I O OxOF ID 3 bytes Set I O 0x10 ID 3 bytes Set ADC DAC Ox11 ID ADC byte DAC byte Configure Ox12 ID 3 bytes Read board version 0x13 ID Returns 0x13 id 2 byte version Motor status 0x14 ID Return 16 status bytes Execute Sync 0x15 0x18 Execute all synchronised commands Board status DCC 7 bytes For more information see the next chapter Command details id id can be 0 1 4 5 8 9 12 13 only ID Board id least significant two id bits are ignored 4 Command details This chapter lists each command the command formal the parameters and ofte
39. ext you only have to send the command to start the motor in a certain direction You do not have to send a stop command at the right time as the Gertbot itself will stop the motor when the end stop switch is activated 4 4 DC Brushed Pulse Width Modulation Motor Frequency OxAO 0x04 id MS gt lt LS gt 0x50 Pulse Width modulation PWM is a technique used to control the speed of brushed motors Instead of lowering the voltage the motor controller provides power for a short period of time and then removes the power Because of the inherence slow mechanical response of the motor it will run slower In fact the mechanical behavior is better than with a lower voltage as the torque of a 1096 PWM driven motor is higher than from a motor with only 10 of its voltage applied This command sets the PWM frequency used in brushed mode The PWM causes pulsed signals to arrive at your motor The coil in your motor is an inductor and pulses with an inductor can cause havoc if you don t know what you are doing see also 10 6 Inductors Working with pulses and an inductor can cause very high voltage Although the H bridges are somewhat protected they cannot withstand infinite voltages So always be careful when using PWM If you set the duty cycle to 10046 there are no pulses an you can reasonably safely connect a DC motor 4period 1 freq a ue The frequency must be between 10Hz and 30 KHz If you change the brushed frequency the program wil
40. he board off But next it asserts the HALT line This will cause the whole system to halt All motors will switch off It also posts an error message telling the user which channel saw an error All other boards will additionally post error messages telling the user that the halt line was activated The user must re enable all motors by sending a start commands to each 7 2 Oscillation If the error is current too high and you have set the processor to ignore that error we get oscillating What happens is the following 1 When a high current is detected the controller channel is switched off 2 This causes the current to become zero 3 As there is no current any more the controller channel is enabled again 4 This causes a high current to appear again and we are back at step 1 Due to the fast switching on and off of the current some motors may produce an audio signal a crackling sound With stepper motors this can cause the motor to take steps and the integrity of the system is lost Oscillating can also happen if the error is temperature too high But the oscillations will be significantly slower as it takes many seconds for a device to cool down and then heat up again 7 3 Brushed motor start stop Brushed motors often draw a lot of current when they start up This is called the inrush current The high inrush current is likely to trip the over current detection and stop the motor again To prevent this from happening the Ge
41. i You plug the board on top of a raspberry Pi If you want to connect more than one board cascade please see the chapter in the Gertbot advanced guide Rev A or B The board has 26 pins as has the Gertbot Raspberry Pi B with Gertbot Revision B The board goes on the outside 26 pins Raspberry Pi B with Gertbot You will find that if you do not plug it in the right way e g misalign by one pin the board will bump against the Ethernet connector 2 12 2 Connecting motors The contacts for the motors are identified on the board using the notion Al A2 B1 B2 C1 C2 DI D2 A motor coil is always connected between X1 and X2 Thus between A1 and A2 B1 and B2 etc 14 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Looking at the top of the board you get these connections Gertbot Top view In order to connect motors and power supplies use the following diagram IE PIA 2 Gertbot 1 1 i 6 ta Gertbot Top view DC brushed motors Gertbot Top view Stepper motors Notice that there is only one ground blue but the top outputs A B and the bottom outputs C D can have a different power supply 15 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 If you ever forget and don t have this manual available At the bot
42. il and thus the rotor will not be anchored As a result the rotor may change position if there is enough external force applied to it This will result in the loss of system integrity Remaining steps When a stepper motor is stopped using a stop eommand or when it receives a new command before it has finished the previous command the system makes a copy of the remaining step counter This value can be read by the user and can be useful in retaining the system integrity The system has only one storage location for the number of remaining steps thus any new step will cause the loss of the previous value The useruse can send multiple stop commands as the remaining steps value is not overwritten when the system is already halted If the attention line is set to indicate steps done it will go low as soon as the step command is started It will go high again when all stepper motors are done 31 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 To start multiple motors at the same time use the sync command system See 4 18 1 Board Synchronous command mode Some examples 100 steps in direction A e A008 00 00 00 64 05 Stepper motor on A1 B2 e A008 02 00 00 64 05 Stepper motor on C1 D2 The bold part is the number of steps To step in the opposite direction use minus 100 e A008 00 FF FF 9C 05 e A008 02 FF FF 9C 05 If you have giv
43. iod has finished 46 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The diagram below shows what this implies Linear start 1KHz stepper start 2KHz stepper start 7 Motor error Each motor controller has two error outputs one for each H bridge This output is pulled low by the motor controller itself when an error is detected Possible causes for an error are e Current too high e Temperature too high An error condition always switches the motor controller channel off This safety measure can not be disabled It reduced the risk of the controller getting damaged _ Formatted No underline 7 1 Reaction to an error The motor error signals are connected to the processor The user can program the controller to take various action if an error is seen A The error signal is ignored B The motor channel is switched off C The pair of channels is switched off D All four channels on the board are switched off E All channels on all boards are switched off A Ignore error This means the processor ignores the incoming error signal Even if the processor ignores the error signal the motor channels H bridge will still be switched off This can lead to oscillations For details see 6 2 Oscillation It is not recommended to run in this mode as your motor controller will be running at the extreme of its operation curr
44. is 12 bits the upper 4 bits of the return value are always zero This command will return 4 bytes 33 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The first byte is the original id The second byte is Ox0C Bytes three and four are the MS amp LS value of the ADC As the command returns 4 bytes it must be followed by at least 4 bytes of 0x50 The ADC converter is operating in continuous conversion mode This means it reads a new value every millisecond and the value is stored The value returned will be the last store value which can be up to 1 millisecond old 4154 14 Read I O 0xA0 OxOE id 0x50 0x50 0x50 0x50 0x50 This command returns the status of all expansion pins To allow space for future boards with more I O the command has 3 bytes but the MS byte is currently unused and always returns 0x00 From MM byte From LS byte Read input byte association table The command dos NOT check which pins are enabled as input It returns the raw data read As such you get the status of special function pins as well Note that the return status of an analog pin ADC DAC is undefined This command will return 5 bytes The first byte is the original id The second byte is OXOE Bytes three four and five are the MS MM amp LS values read As the command returns 5 bytes it must be followed by at least 5 bytes of 0x5
45. ite magnetic fields but in this case the full coil is active so the magnetic field we can generate is twice as strong But to drive the connections from A B 56 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 to the inverse A B you need more than two switches If you have read the previous paragraphs it will be obvious that this can be achieved with an H bridge For two sets of coils you need two H bridges 030 RT Ww Ld PT A stepper motor with four wires is not much different from one with six wires The middle taps of the coils are missing f ON o eon 10 5 2 Mechanics Most stepper motors have a permanent magnet with teeth which is mounted on the axis The following are a set of diagrams which try to explain the principle of operation The current in the external coils is changed such that the rotor is moving from one position to the next ENEKE Ba n S i e N In reality the internal of the motor is much more refined with many small teeth and two sets of teeth on the rotor The two sets of teeth are slightly offset and the magnetics are controlled in such a way that the rotor switches from one set of teeth to the other 10 5 3 Rotor hold From the pictures in the diagram above you can see that the rotor will be held in place if the
46. l set the corresponding duty cycle for you You can change the duty cycle whilst the motor is running Do not use a low frequency with big DC brushed motors as it will cause extreme high inrush currents and that is likely to trip the over current protection It is will also to make the controllers very hot especially if you disable the high current trip See also 7 3 Brushed motor start stop 4 5 Brushed Motor Duty Cycle OxAO 0x05 id MS gt lt LS gt 0x50 This command sets the Pulse Width modulation PWM duty cycle used in brushed mode The value must be between 0 and 1000 The duty cycle is specified in step of 1 1000 of 100 Thus 100 is 10 500is 50 etc Setting a duty cycle of 10096 0x0A 0x05 id 0x03 OxE8 0x50 gives a signal which is constantly high DC output on the motor pins Unless you start rapidly switching your motors on off or forward backwards 28 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 amp p ee es lt B gt The duty cycle is time A divided by time B The picture above shows a duty cycle of 25 0x0A 0x05 id 0x00 OxFA 0x50 The duty cycle is maintained even if you change the frequency Default after enabling the duty cycle for a brushed motor is set 100 by the system Unfortunately the hardware does not allow the duty cycle and the frequency to be independently set Thus the Gertbot updates the
47. mmands bits of these two tables The baud rate is set to 57600 baud and it requires 20 baud clock cycles to transfer a direct command This means you can send single step commands at maximum 2880 Hz to one board At the moment direct stepper motor commands have the same behavior as normal stepper commands in that a new command replaces a previous possible pending command Thus a previous command can be overruled and replace with a new command if it has not yet finished 6 4 2 Synchronous commands Currently only the motor start stop and step commands can be executed synchronously The synchronous mode is enabled or disabled using the board setup command See 4 18 Board configure In synchronous mode the execution of the two start stop motor commands e Start Brushed Motor OxA0 0x06 id mode 0x50 e Take steps OxA0 0x08 id lt MS gt lt MM gt lt LS gt 0x50 is postponed until a sync command arrives Thus you can send take steps command to all stepper motors and then start them virtually at the same time using the sync command If you send multiple commands to the same motor before the sync is sent only the last command is executed All previous commands are lost There are some details to keep in mind e There will still be a small delay of max 4 micro seconds between the starting of the motors e The stepper motor timer is started on the sync command The actual step will only take place after the stepper per
48. n examples Each command that generates a response from the Gertbot The Gertbot send back a number of reply bytes has to send multiple closing bytes Value 0x50 To be precise if a command returns X bytes the command must be followed by X times the 0x50 value Throughout this document you will find references to Direction A or Direction B I use the terms A and B as the real physical direction depends on how the motor wires are connected e g for a brushed motor the direction inverts when the two wires are swapped 4 1 Read version 0xA0 0x13 ID 0x50 0x50 0x50 0x50 This command returns the version of the board indicated with ID ID can be in the range 0 15 but the LS two bits are ignored This command will return 4 bytes The first byte is the original ID 23 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The second is 0x13 Bytes three and four are the MS amp LS values of the version code As the command returns 4 bytes it must be followed by at least 4 bytes of 0x50 4 2 Operation mode OxA0 0x01 id mode 0x50 This command sets the operation mode of a motor The id can be in the range 0 15 for brushed motors The id must be even for stepper motors If you set a motor up as stepper motor the following motor with id 1 is disabled Thus if you set motor 0 to stepper mode you can no longer send commands to motor 1 You can NOT set motor
49. ols cp start all engines bin dev ttyAMAO Identifier Copyright O 2014 Fen Logic Ltd 21 The copyright is on the manual as well as the instruction set 1d Formatted Keep with next 44 pm Formatted Keep with next lt Formatted Keep with next Formatted Keep with next Formatted Keep with next Gertbot Rev 2 3 September 2014 ID Board Connections ID Board Connections 0 0 A1 A2 8 2 A1 A2 1 0 BI B2 9 2 BI B2 2 0 C1 C2 10 2 C1 C2 3 0 D1 D2 11 2 D1 D2 4 1 A1 A2 12 3 A1 A2 5 1 BI B2 13 3 BI B2 6 1 C1 C2 14 3 C1 C2 7 1 D1 D2 15 3 D1 D2 If you are operating stepper motors you need two pair of connections for one stepper motor Thus the four connections Al A2 B1 and B2 together control one stepper motor The same holds for the set of C1 C2 D1 and D2 which together control another stepper motor As all of those MUST work in unison a stepper motor id can only be even 0 2 4 6 8 10 12 Thus sending a command to id 0 will control all four of the outputs Al A2 B1 B2 Stepper motor commands send to an odd ID will be ignored and raise an error Some commands are not designated for a motor but for the board itself In that case the ID value 0 1 2 3 are all treated as for the first board ID values 4 7 address second board etc 3 2 Values Many commands take one or more parameters As mentioned
50. ontroller simple a DCC command is always send as 10 bytes 39 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Destination The DCC command are unique in one other way You do not send commands to a specific channel DCC commands can be send to any or all four channels simultaneous The MS bits of the format byte indicate to which channel the message should be sent Bit 7 set send to channel 3 Bit 6 set send to channel 2 Bit 5 set send to channel 1 Bit 4 set send to channel 0 Thus when setting all four bits the message is sent to all four channel simultaneously If an output is not configured for DCC mod the data is not send to that output The destination is silently ignored This is the only time that no error message is generated although an illegal command has been sent It allows the user to send DCC commands everywhere all the time The LS 4 bits of the format byte indicate the message length This is the number of bytes which will be send to the output This is NOT the number of bytes send to the Gertbot You always send 10 bytes to the Gertbot You do not have to send the checksum byte as that is calculated by the Gertbot and t is automatically appended You also do not have to repeat the message as the Gertbot will send the message a number of times Pacing The DCC output rate depends on the number of times a command is repeated The raw rate i
51. op board or stop all boards e I O pins programmable functions e Emergency stop halts whole system The board comes with drivers example code and a GUI all complete with source code Depending how fast you can screw the wires down you can have your motors running in a few minutes used the term brushed motor to indicate the standard DC brushed motors You find those in most toys 1 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The board can also be used to drive other power electronics like LEDS relays etc Using a 30V supply and 2mA LEDS you can drive three sets each of 12500 RGB LEDS using the boards PWM feature to control the colour READ THE MANUAL The most difficult part of controlling motors has been taken care of by the software running on the Gertbot Instead of directly having to manipulate the motors you send high level commands to the Gertbot which will execute them But this does mean that you have to learn what those commands are Therefore you should read the manual Quick start For those of you who want to start quickly there is a Gertbot GUI which you can use to control every feature of the Gertbot There is a separate Gertbot GUI manual which guides you through the controls but it refers to this manual to explain the details of operation Advanced The Gertbot Advanced guide helps you with cascading board
52. ors in the Gertbot Advanced Guide If all four channels work in parallel the board can handle 10Amps Note that this is the only way in which you can guarantee that all outputs are in perfect synchronisation 6 Operating details 6 1 End stops Often a motor is controlling a mechanical part which is limited it its movement In that case the motor should not move the mechanical part beyond a certain limit Therefore there are switches mechanical or optical which tell the motor to stop moving in that direction This is what is called an end stop in this manual It is not possible in this manual to talk about the direction of a motor The direction depends on how the user connects the motor wires By reversing the wires the direction changes Therefore I use the nomenclature A and B When a motor is moving in direction A it is stopped if end stop condition A is seen The other end stop B has no effect on the motor when it is moving in direction A 41 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Direction B Direction A Direction B End N stop p End 1 stop a 3 A Each motor has been assigned two input pins which can be programmed as end stops If an end stop is active the motor cannot be started to move further into the end stop direction If an end stop becomes active and the motor is moving into its direction the moto
53. ot connect the board to an RS323 port RS232 has a voltage swing between 3V and 15Volts It will damage the board The requirements te eenneetfor a serial port te the Gertbet are Formatted Space After 0 pt Keep with next e Amplitude 3 3 Volts Formatted Keep with next e 57600 baud e 8 data bits e start bit e stop bit e No parity Thus any equipment which can read and write a serial UART stream can be used to control the boards The board does not use flow control There are three ways te conneet a serial eable Other than plugging the Gertbot to the top of a Raspberry Pi here are three ways to connect a serial device 2 6 12 7 1 Connect to J12 cascade connector This is the easiest way but prevents you from using more than one board You will need an 8 pin female header organised as two rows of 4 pins 0 1 pin pitch Connect the signals as follows Signal Pin Pin type on Gertbot Ground 1 Ground 5Volt 65mA 3 Power Transmit 6 Input Receive 4 Output Attention Optional 5 Output Transmit is the transmit pin of your external computer It is a receive pin of the Gertbot Receive is the receive pin of your external computer It is a transmit pin of the Gertbot 19 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Below is a picture of a FTDI USB to TTL cable connected to J12
54. owing table shows the soft start value and the start up time in seconds 29 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Code Time Code Time Code Time Code Time 0x0 Off 0x4 0 75 0x8 1 75 OxC 3 Ox1 0 1 0x5 1 0 0x9 2 OxD 4 0x2 O25 0x6 1 25 OxA 225 OxE 5 0x3 0 5 Ox7 1 5 OxB 2 5 OxF 7 Soft start time is used when steppine motors in seconds To start multiple motors at the same time use the sync command system See 4 18 1 Board Synchronous command mode The linear stop command is an exception in that it is also used to stop stepper motors See also 4 8 Stepper motor take steps Example start command OxA0 0x06 0x01 0x010x71 0x50 Start board 0 motor 1 in direction A ramp up in 1 second 4 7 Brushed Meter Ramping 4 84 7 Read error status OxAO 0x07 id 0x50 0x50 0x50 0x50 30 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The system keeps track of the last 16 errors This command will return the status of the most recent error If there are no more errors the return value will be 0 This command will return 4 bytes The first
55. pyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 10 Appendix B Technology So you want to start playing with motors but you have no idea where to start To begin with I can t teach you all there is to know about this subject First because I don t have the time second because I don t know it all either even after forty five years in electronics Fortunately the internet is a wonderful source of information at least on the technical level where most of the information seems to be true So read up use search engines use Wikipedia What follows is just a short brief explanation of terms you might want to get familiar with 10 1 DC voltage A Direct Current power source which gives out a constant voltage and current It is often show using this symbol Batteries are such a source as well as most power bricks which you plug between the power socket in your house and some equipment It seems that a DC voltage below 60V is deemed to be safe but I suggest for these motors you do NOT use anything above 18V unless you know a lot about electronics and electricity and are certain about what you are doing Which is probably NOT the case otherwise you would have skipped this section Why Read the next sections 10 2 AC voltage The opposite of a DC power source is an AC Alternate Current which is what comes out of your home socket AC power sources are much mor
56. r is set up as stepper motors all command for the pair must go to the lowest id There are two stepper motor modes each has a different waveform After sending a mode to a motor you must specify a frequency before the motor can be used even if the motor was already in that same mode DCC stands for Digital Command Control A method of controlling model railway objects 24 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Mode 1 Stepper motor mode 1 uses gray coded outputs wa l1 Ll wel F1 uu 11 Ll m 1 l5 Figure a Mode 1 gray waveform positive steps wal 4 1 uo 1 F l14 uw 1 L wm l1 F LI Figure b Mode 1 gray waveform negative steps Mode 2 Stepper motor mode 2 uses pulse coded outputs arl Ll Tl A2 C2 B1 D1 B2 D2 Figure c Mode 2 pulse waveform positive steps 25 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 A1 C1 A2 C2 B1 D1 em LOO l1 Figure d Mode 2 pulse waveform negative steps Mode 3 7 are not yet used Mode 3 is reserved for wave output wa IL uc LI L uw D LI oon l1 LI Mode 8 Mode 8 is for DC brushed motors In brushed mode the board supports Pulse Width Modulation PWM to control to motor speed For details about PWM see 4 4 DC
57. r is stopped End stops can be enabled disabled and can be programmed as active high or active low The following table shows the relation between the motors the end stops the inputs associated and the travel direction it guards Motor End stop Pin Brushed direction Stepping Direction 0 A Ext0O 1 binary 01 Positive 0 B Extl 2 binary 10 Negative 1 A Ext2 1 binary 01 1 B Ext3 2 binary 10 2 A Ext4 1 binary 01 Positive 2 B Ext5 2 binary 10 Negative 3 A Ext6 1 binary 01 3 B Ext7 2 binary 10 End stop association table The end stop system works only if the user has set the motor direction correctly The Gertbot associates a motor travel direction with an end stop Travel direction A means to motor is expected in due time to active end stop A If you find the motion is in the opposite direction there are two ways remedy this 1 You can swap the wires of the two end stops A and B around 2 You can invert to motor rotation direction You can change the direction of a brushed motor by swapping the two wires You can change the direction of a stepper motor by changing multiple wires See the operating manual of your stepper motor End stop polarity The end stop inputs have a pull up resistor Thus if an end stop is not connected it will read as high 1 From that it seems most convenient to use active low end stops However it is better to use active high end s
58. rdO system Motor 0 Motor 1 DC brushed More or More 5000 Frequency 100 0 cj Duty Cyde u You can now play with the buttons and your motor should run 100 0 4Duteyde i00 vj Ramp s 9 None gt 0 05 Copyright 2014 Fen Logic Ltd Tl 0 12 0 25 0 37 0 50 7 0 75 alas well as the instruction set 1 25 Gertbot If you have a big motor the over current protection might kick in This can be so fast so you will not notice it All you find is that your motor does not start If so press the More button and set the Ramp Up speed to 1 second See 7 3 Brushed motor start stop for details about that Copyright O 2014 Fen Logic Ltd Rev 2 3 September 2014 r Motor 0 Formatted Right 11 26 cm Bees a 10 The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 9 For stepper motors you see this ccr EE s uis Connect con 15 x Read Status Read Error s I m T T Re Send I Pot M Log Sync Board 0 System p Motor 0 Motor 1 Motor 2 Motor 3 Off Y Off Y Off ed us High Hiah High EndstopA T I EndstopA F F EndstpA F F Endstopa F EndstopB M F Endstopp Endstopg F E dstps M 100 Frequency 0 Frequency 0 Frequency 0 Frequency Connect Com 15 lt 4
59. reached In that case you must program the end stop as active low 17 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Alternative you can connect a switch which is normally closed and gets opened if the end stop position is reached In that case you must program the end stop as active high This is the preferred way of connecting an end stop If you use end stops you MUST make sure your motor s rotational direction is correct The simplest way is to use the GUI and use the button of the GUI to make the motor move into the direction of end stop A If the motor goes into the opposite direction swap your motor wires around or swap your end stop wires around Also test your end stop There are two ways to do this 1 Set the motor moving operate the end stop e g with a finger and check that the motor stops 2 Operate the end stop and check that the motor refuses to start in that direction If it does not work blame your circuit not the Gertbot as that has been thoroughly tested Did you connect to the right ext pin did you set the correct end stop mode and polarity 2 52 6 Connecting Open drain output The Gertbot has two open drain ports The switch element is an NMOSFET Each can switch 30V 3A The following picture shows the open drain connections Gertbot open drain connections For those who are no familiar with open drain connections An open dr
60. rtbot system provides a soft start or ramp mode In this mode the signal duty cycle starts at zero and is slowly increased till the value the user has selected There are no electrical issue when stopping a motor but there may be mechanical reason where you do not want a motor to stop abruptly Therefore the Gertbot also offers ramp down There are situations where you do allow the motor to stop as soon as possible Thus the Gertbot offers a second ramp down speed the halt time 48 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 When the HALT signal is activated the controller removes the power from all motor on all boards immediately There is no ramp down time There are 16 ramp values which give a range of times Code Time Code Time Code Time Code Time 0x0 Off Ox4 0 75 0x8 1 75 OxC 9 0x1 0 10 0x5 1 00 0x9 2 00 OxD 4 0x2 025 0x6 1 25 OxA 225 OxE 5 0x3 0 50 Ox7 1 50 OxB 2 50 OxF 7 Ramp time in seconds The value gives the time it takes for the duty cycle to get to 100 If the user has set the duty cycle lower the soft start will take proportionally shorter Thus if the duty cycle is set to 50 a ramp value of 9 will take 1 seconds to get to the desired 50 DC speed Not 2 seconds Start ramp The start ramp time is used when the user gives a motor start command Stop ramp The
61. s The force it can apply also goes up with the voltage Unfortunately this means the running a DC motor slowly and still providing a lot of force is not possible 55 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 CN Y e Oe we You can reverse the direction of rotation by reversing the voltage over the wires or by swapping the wires around which is the same 10 5 Stepper motor 10 5 1 Connections Most stepper motor come with four or six wires The following is a diagram of a stepper motor with six lt MM Ww To generate a magnetic field you have to send a current through one if the coils There are several ways of doing this Here we connect the middle of a coil to the and then we can use two switches to enable either one or the other coil Ww pT The blue arrow indicate the direction of the magnetic field As you can see the two operating modes have opposite magnetic fields I have not drawn it but you can imagine that the same is possible with the coil at the bottom The advantage of this method is that you need only two switches to flip the magnetic field of the coil around But the disadvantage is that you use only half of each coil For two sets of coils you need four switches In the following diagram we drive the coils from their extreme connections The middle tap of the coil is not connected to anything Again we get two oppos
62. s operate bridges in parallel to double or quadruple the maximum current It also tells you how to upload new software versions or how erase the current program and put your own software on the board Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Contents 0 DLwantto seat NOW List nep P DET CARO CR eG WEGE UE ahaa 5 Dt Overviewdo cute I EN LC men EU OE UE EE 13 Ib SEES eerte ERES IEEE NIE RUAN ETUR Pro eettersiseke EEE nes soso tenes tp devas 13 2 Connecting things p inceei reris e re en e E EU XE FQ RE PO ERE EE RRR 14 2 1 Connecting Gertbot to a Raspberry Pi oo cece ceeeseeceeeeeseeesecseeeseesseceececesecseesseeeeeeeeeseeeees 14 2 0 Connecting MOLOTS 2 nn erect n e E RO REPE CH LE X PY EP TREE RET T E gu 14 2 3 Connecting stepper motors cease heri trees er e Pet REESS ETER SERERE RECENTE ERR RR RREE SERERE Eat 16 2 4 Connecting Motor DOWGE 2 eerte iere rid der I i SEX HER EXPO ERE SERI RECO ERE DIRE SRI re ERE sna db 16 2 5 Connecting end stops i iei carrier a eere eter iners o Ie REEF Coa REN RNC FEE ERR Reda ad 17 2 6 Connecting Open drain output rennen erinnere nreten nnne 18 2 7 Connecting to other then Raspberry Pi eeseseseeseeeeeeeeee nennen nenne 19 2 7 1 Connect to J12 cascade connector ssssssssssseeeeeeenen nennen eene n nnne 19 2 7 2 Connect to J6 PI Connector ihi
63. s about 6 3Kbits sec If each message is repeated four time that drops to 1500 bits seconds The data rate to the Gertbot is 57Kbits sec Thus you can send commands thirty faster to the Gertbot then it can output them Thus there is the potential of overloading the system The Gertbot checks its output queue to see if a new message will fit The current queue size is 128 bytes If there is not enough space the whole message is discarded and an error is generated Thus you do not have to worry about partially messages upsetting the system No synchronous output The four output channels are treated as independent entities Thus it is not possible to connect the four output to the same track If a higher current is required you must make a physical modification to the board connect the output drivers in parallel For information how to do that see the Gertbot Advanced Guide 5 1 DCC command 0xA0 0x19 id format address data lt data gt lt data gt lt data gt 0x50 Examples Send 0x03 0x40 to channels 0 and 1 on board 0 0x0A 0x19 0x00 0x32 0x03 0x40 0x00 0x00 0x00 0x50 Send 0x10 0x11 0x12 0x13 0x14 to all four channels on board 1 Ox0A 0x19 0x04 OxF5 0x10 0x11 0x12 0x13 0x14 0x50 5 0 DCC configure 0xA0 Ox1A id repeat preamble DC lt flags gt 0x50 This command is used for DCC configuration 40 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2
64. s set as DAC will remain operating as analog output In effect to use a pin for input or output you must first disable its special operating mode That must be done with a separate command The following table lists how to make the pins available for input output mode 35 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Pin How to reclaim for user access EXTO Disable motor 0 end stop A EXTI Disable motor 0 end stop B EXT2 Disable motor 1 end stop A or use motors 0 1 as stepper EXT3 Disable motor 1 end stop B or use motors 0 1 as stepper EXT4 Disable motor 2 end stop A EXTS Disable motor 2 end stop B EXT6 Disable motor 3 end stop A or use motors 2 3 as stepper EXT7 Disable motor 3 end stop B or use motors 2 3 as stepper ADCO Disable ADCO channel ADCI Disable ADCI channel ADC2 Disable ADC2 channel ADC3 Disable ADC3 channel DACO Disable DACO channel DACI Disable DACI channel HALT Cannot be reclaimed Expansion connecter pin reclaim table 4184 17 Set ADC DAC 0xA0 0x12 id gt ADC gt lt DAC gt 0x50 This command enables or disables the on board ADC and DAC channels A reason to disable a channel is to use the pin on the expansion connector for user input or output The LS 4 bits of the ADC byte enable or disable an ADC channel Bit 0 enables disables ADCO bit 1 enables disables ADC1 etc If the
65. t line itself is active low The ATTn status bit reflects the actual status of the ATTn line As the command returns 5 bytes it must be followed by at least 5 bytes of 0x50 4214 20 Read motor status 0xAO 0x14 id 0x50 0x50 This commands returns some status information of a motor This command will return16 bytes lt Formatted Don t keep with next The first byte is the original id 38 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 The second byte is 0x03 Bytes2 16 have the motor status packed in them The following table shows what the return status bits represent This C code extracts the information status mode rec 2 amp OxOF status ramp rec 2 amp OxF0 gt gt 4 status gt endstop rec 3 amp 0x3 status gt endstop polarity rec 3 amp 0xC gt gt 2 status gt move rec 3 amp OxF0 gt gt 4 status gt frequency rec 4 lt lt 16 rec 5 lt lt 8 rec 6 status duty cycle rec 7 lt lt 8 rec 8 status gt steps rec 9 lt lt 16 rec 10 lt lt 8 rec 11 status gt remainder rec 12 lt lt 16 rec 13 lt lt 8 rec 14 5 Digital Command Control Digital Command Control DCC is a system to control model trains The Gertbot was not originally design to perform this function but it turned out that the hardware and microcontroller where powerful enough to add this f
66. t ADC DAGQ p oscila eee o He Rn o b eee ots 36 4 18 Board configure cene aee hee b a e e d e OR ere bee ia 36 4 18 1 Board Synchronous command mode sssssssseeeeeee eene 36 4 18 2 Attention signal mode e a a eane aaeeea ae ATEA eene nennen ennemi 37 C MESS MEME Iv 1 E K0 RR T EP 37 4 18 4 Board configure command overview esee nennen rennen 37 4 19 Read board status oe eere er ee rer rr eR Ce een Ree Pe IHR TR ia 37 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 4 20 Clear error522 iluce nnne to eere p i RR Ferre Error Bookmark not defined 4 21 Read motor status reo ed eR DRE CH E E A A i a TET ga Peg 38 5 Digital Command Control 25 ctt n Fi e eoe e rea ci t anna ee E den 39 5 1 DEC Command nonet ion er HE REB EO E PARERE NET ME EE A MER UNE ag eui Rea Red 40 SEEDS OC nibo Er x EAS 40 5 3 Connecting It Up iore eoe REY ARMES REI RAE REED SUE TE CH DRE ee DESEE KS HIE Ere Re EL EE Pa S 41 6 Operatng details oce ERE DOR ER ERR ET DOR YO E DECEMB ORI EE DERE 41 6 1 End Stops necat eene e e YD HR e EE aes eRe 41 6 2 Haltestelle ect tab ed eat st indeed ada 43 6 3 Frequen y SettlDgs cecinere CITUR pp eh v eene ir aee ae rare re caia 43 6 3 1 Arc pA 43 6 3 2 Zeune 43 6 4 Synchronous Oper tlOnD s s iced retenti aSK aet PRSE Rete de Pe EUER p PEDE Fea RR REYN AVR SEEN XR Se EEs 44 6 4 1 Direct
67. tatus bits represent 37 Copyright O 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Gertbot Rev 2 3 September 2014 Value MM byte bit System status byte association table This command will return 5 bytes The first byte is the original id The second byte is 0x03 Bytes three four and five are the MS MM amp LS values read The status bits are such that a high bit indicates a special or error condition The ESO ES7 lines indicate the end stop active values If high the end stop is activated and hopefully the motor has been stopped On the board an end stop signal can be active high or active low The micro controller takes that into account when producing the board status bits and corrects the polarity Thus a high status bits always means an active end stop The ENB A ENB D status bits are the status of the motors controller error lines High 1 means an error You are unlikely to see these lines active when the current is too high as the controller is immediately switched off This means that if you read one of these lines as high there is a high probability that the chip is too hot TO DO latch A D error status bits Low 0 means no error Note that the ENB AB and ENB_CD line themselves are active low For details see chapter 6 Motor error The HALTED bit is high if the HALTn line is active and the system is in the halted state Note that the Hal
68. tom of the board you find a diagram which shows where to connect the motor coils and the power supplies Safe MAX 18V 2 5A rms Coil PIE A2 A1 VAB B1B2 Gnd C2 C1 VCD D1 D2 Gnd Gertbot BOTTOM VIEW 2 22 5 Connecting stepper motors Brushed motors have a high impedance and you can connect a brushed motor direct to the board This is not the case with a lot of stepper motors Beware Some stepper motors may need series resistors to connect them to the board The controller needs a minimum of 8V to work If your stepper motor requires less voltage you must add series resistor If you connect up a stepper motor you will need to use a pair of connections Thus a stepper motor connects to Al amp A2 and B1 amp B2 Most likely your stepper motors has four or six wires For details about stepper motors see chapter 10 5 Stepper motor 2 32 4 Connecting motor power For a motor to run you must connect an external power supply The motor controllers should be connected to a power source between 8 and 18Volt For safe operation do not connect more than 18volts The board can withstand operating voltages up to 30V but anything above 18V can cause dangerous voltage levels to appear on the motor output pins The bridge controllers need a minimum of 8V If the input voltage is below 8V the controller will refuse to work The power is connect with the plus connected to pin VAB or VCD The ground goes to the Gnd
69. tops If possible you should always use active high end stops The reason is that if for some reason the wire between your end stop switch and the board brakes the end stop will become high and thus indicate a stop With an active low end stop the motor will hit the switch which is no longer connected and keep traveling 42 Copyright 2014 Fen Logic Ltd The copyright is on the manual as well as the instruction set Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Formatted Space After 6 pt Line spacing Multi p e 1 1 li Gertbot Rev 2 3 September 2014 For more protection you can add a second switch after each electronic stop which is in series with the motor power If the first switch fails the second one will cut off the power to your motor But you then have to manually rotate the motor
70. unctionality DCC mode can be set for each channel separately This allows the user to have four independent DCC channels But you can again mix and match For example have two DCC channels and two analog channels The DCC mode has been tested with train equipment donated by Hornby Thank you Ken There is a rudimentary system for playing with the DCC system in the Gertbot GUI but to use the Gertbot with a real train emplacement a new GUI should be written A task I have to leave for others due to a lack of time Format DCC commands are send as packets There are rules how to send packet which you do not need to know as the Gertbot will take care of that The Gertbot will also take care of repeating the packets Beware that the system does not infinitely repeat the packets as some controller do It send a packet N times The value of N is programmable and then no longer If you want commands to be send repeatedly e amp every 10 seconds you have to program your computer to do that There are two DCC commands One to send packets the other to configure the Gertbot DCC parameters If an output is set up in DCC mode the user can send command to the board which will then be transferred to the outputs A DCC command is between 3 and 6 bytes long where the last byte is a checksum byte The Gertbot will calculate the checksum byte so you should not send that Which means DCC commands for the Gertbot are 2 5 bytes long To keep the software in the c

User manual ()

Contents

Download Pdf Manuals

Related Search

Related Contents