BeBoPr++ Manual v1.4.2
Contents
1. SERENA PERF EE PRIN ANE PV SE 22 BeBoPr t improvements eon eiusd ess NR ER T RE RR DU EN 22 Free whieeling diodes iiie icis ee eroe o arena nr ek sk RE ERKESEVER EO NES USE 23 Power VOR EV ERES 23 iei cr 25 Signal 1 REN M A DU 25 lese 26 DC ANG 26 PR dE 26 Thermistor CUl 26 Plug in stepper vens o qaia ed ERES a E nEUPEE ae iaiacaegneanseeeaspetaveauees 28 enable Mer PTT MT 30 Indicator LEDS M RET c ends 31 DEDS PRU OE E KERENRSVRNNNNESIAFEREHRSSEESQEA ATE RE Ker xA 32 Status LEDS e c M et 32 Input SIONAL Rap EET J 32 O tp t signal LEDS P 32 version 1 4 2 27 02 14 page 3 BeBoPr User Manual ae Tu bU SURE CMM uude cus dts 33 PI 34 Jump6ets Ro eur SANARE TUA QUACEPE WE E EAS ase DAR adus ERE RR ER2. It can be seen on the cover photo next to the two push buttons This connector is divided in two parts and accepts either one single 6 pin mating part or two separate connectors one 4 pin part for the I2C bus and one 2 pin part for the emergency stop signal Emergency Stop Input The ESTOP input can be used to disable all outputs in case of an emergency situation The active emergency stop state is indicated by a red LED D24 close to the ESTOP connector As long as the ESTOP state is asserted the I O enable signal on the board will be suppressed in hardware No software is involved By default the emergency stop signal is level sensitive If jumper JP2 on the back side of the board is closed the signal becomes edge sensitive A short activation of the ESTOP state will then be latched to remain active until the board s O enable signal is negated briefly via software The ESTOP signal should connect to a normally closed contact or some open collector open drain type sensor When not used a jumper or piece of wire can replace the sensor An external opto coupler isolator can be used to interface to 24 Volt signals A normally closed contact should pull the ESTOP input low to GND during normal operation Breaking the contact will activate the emergency stop state An opto coupler with open collector output can be used to interface with industrial level e g 24 V signals This way the board can be used without when the emergency
3. drivers and the connectors J15 J16 J17 and J19 are not used The stepper signals for the external drivers connect to J5 Thermistor connectors Designed for use with 100kQ thermistors e g Epcos B57560G104F or any low impedance analogue signal source For the latter one should take into account that a 3 60 Volt voltage source with an internal resistance of 2 05 kQ is connected parallel to the input pins J6 Thermistor 0 BeagleBone AIN4 and ADS1015 channel 0 J7 Thermistor 1 BeagleBone AIN5 and ADS1015 channel 1 J8 Thermistor 2 BeagleBone AIN6 and ADS1015 channel 2 Limit switch connectors J9 X max limit sensor BeagleBone gpio69 J10 X min limit sensor BeagleBone gpio67 J11 Y max limit sensor BeagleBone gpio26 J12 Y min limit sensor BeagleBone gpio68 J13 Z max limit sensor BeagleBone gpio33 J14 Z min limit sensor BeagleBone gpio27 All limit switches have a 5 Volt supply pin pin1 a ground pin pin 3 and a signal pin in between pin 2 The input is pulled high to the 5 Volt by 560 pull up resistor in series with a LED Connecting pin 2 to the ground pin 3 will activate the LED and change the signal on the gpio pin of the BeagleBone to a 1 active Because of the hysteresis built into the input level shifters these can connect directly to optical slot sensors with an open collector like output In that situation the LED may continue to glow weakly in the off situation but that is cle
4. heaters for a 3D printer does not require high speed switching Switching between 1Hz and 100 Hz makes the switching losses marginal and only the current through the FET and the FET s internal temperature are important Power dissipated the FET is proportional with the current squared When a 4A current flows through the FET and the sum of Rdson and other resistive elements in the FET is 50 milliOhm a 200 mV voltage drop over the FET generates 0 8 W of dissipation in the FET If we increase the current to 6A assuming the FET is still kept at the same temperature the dissipation in the FET rises to 300 mV x 6A 1 8 At 8A the dissipation reaches 3 2 W four times the dissipation at double the current But another effect gets important If the temperature of a FET rises the Rdson increases too The Rdson will double if the FET s internal temperature rises from 25 degrees to 175 degrees Celsius This resistance increase of 100 will also increase the power that is dissipated in the FET with 100 The resulting temperature rise will increase the resistance further Increasing dissipation and temperature even further This so called thermal run away must be prevented by cooling the FET adequately If dissipation in a FET is kept below 1 W and ambient temperature is normal no further cooling of the FET is necessary Above that precautions have to be taken to keep the FET cool The first step is to use a clip on he
5. J20 may not exceed 16A Power supplied to the digital input connectors 5 0 Volt 5 TBD depending on load Short circuit protection in case of a short circuit the current will be reduced to less than 0 3A within 30 seconds by a thermal PTC type fuse F4 PWM power outputs Output PWM2 J4 can deliver 10A at 12 Volt 120W or 8A at 24 Volt 200W Outputs PWMO J2 and PWM1 J3 can deliver 4A each Note The combined output currents may not exceed the rated 16A for the supply connector Short circuit protection by a non resettable 5x20 mm cartridge fuse F1 The stepper output signals on J5 are 5 Volt CMOS level compatible Pin 16 connects directly to the BeagleBone once jumper JP3 is closed The voltage on this pin should never exceed the 3 3 Volts maximum rating of the BeagleBone s processor or the BeagleBone will be damaged The Pololu StepStick boards are driven by 5 Volt CMOS level signals Stepper Power input The voltage that may be applied on this input is determined by the specification of the stepper modules and the components on the BeBoPr The BeBoPr uses components specified for 50 Volts but because of the voltage peaks that are generated by the motors the maximum allowed working voltage is 35 Volts Note that many stepper driver modules have an even lower maximum operating voltage The voltage on this input should not exceed the lowest value of all these specifications Sensor inputs are 5 Volt TTL level compat
6. Volt levels version 1 4 2 27 02 14 page 38 BeBoPr User Manual J6 J7 J8 Pin nr Direction analogue inputs 1 IN Positive terminal 2 GND Negative terminal J9 J10 J11 J12 J13 J14 Direction digital inputs 1 OUT 5 Volt supply 200 mA max over all connectors 2 IN Input switch to GND 3 GND Pin nr Direction J15 J16 J17 19 stepper motors 1 OUT Stepper coil 1A 2 OUT Stepper coil 1 B 3 OUT Stepper coil 2 4 OUT Stepper coil 2 B Pinnr Direction stepper input 1 GND 2 IN Positive terminal stepper power Pinnr Direction Beard input 1 GND 2 IN Positive terminal input power Pinnr Direction 12C ope 1 GND 2 IN OUT SDA 3 IN OUT SCL 4 IN External VCC 3 3 5 0 Volt 5 IN ESTOP 6 GND version 1 4 2 27 02 14 page 39 BeBoPr User Manual Mating Connectors The connectors used on the BeBoPr are the same types as on the BeBoPr and BeBoPr boards On the BeBoPr connector J22 was added This connector was split into two sections J22A the I2C part and J22B the ESTOP part This way a single 6 pin connector or separate 4 pin and 2 pin connectors can be used for the wires When shipped the BeBoPr has a red jumper mounted on J22B to prevent the ESTOP circuit from getting activated I O connectors The pin header connectors on the b
7. bang or simple on off control The output closest to the board power input connector J20 is dimensioned to deliver 120 W to 200 W depending on the voltage used 10A 12 Volts or 8A 24 Volts The other two outputs can deliver 4A each 50 W 12 Volts or 100 W at 24 Volts Note that the combined current drawn should not exceed the 16 A specification The power switching FETs have very low Roson and are driven by MOSFET drivers They can operate at high switching frequencies with relatively low switching losses Connecting inductive loads can cause all kinds of trouble ranging from HF noise up to a damaged BeBoPr Always use a free wheeling diode directly over the load This keeps the current loop coil as small as possible and reduces the area polluted by the EMI noise Use of high current loads may require forced air cooling of the board FETs diodes and fuse This prevents parts from overheating melting the solder and possibly destroying the BeBoPr your home or even worse Make sure to also read the chapter on FET power dissipation Always be careful start conservative and test Increasing power only if you feel comfortable with the results of the previous step version 1 4 2 27 02 14 page 12 BeBoPr User Manual Warning Some of the components can get very hot too hot to touch If in doubt use a moistened finger before probing a package Never ever leave your system unattended when playing with these kinds of
8. features on an early prototype Power The on board switching step down converter creates the 5 Volts DC required for the BeagleBone BeBoPr and external digital inputs Configuration EEPROM The BeBoPr uses an on board EEPROM to identify itself to the BeagleBone version 1 4 2 27 02 14 page 16 BeBoPr User Manual For 3 2 kernels used by the original BeagleBone the pinmux configuration is read from the EEPROM during kernel start up All inputs and outputs are configured accordingly this requires kernel 3 2 16 or later The 3 8 kernels used by the BeagleBone Black have a different way to set the pinmux configuration During boot the identifier is read from the EEPROM and the corresponding Device Tree Overlay is loaded The DT overlay defines the configuration of the inputs and outputs as wel as the configuration of various subsystems from the processor The EEPROM address of the BeBoPr cape is factory set to 0x54 Daughter modules 29 tt rm i 4 i a dne 19 Beagl Bone Illustration 3 BeBoPr daughter modules The BeBoPr cape is designed to act as base board for the BeagleBone module and optionally the stepper driver modules as shown in the illustration below Because of the board size and the amount of cables needed to connects all devices to the BeBoPr the stacking order has been reversed and the Beagle
9. high currents The intention is to generate heat but sometimes the heat will appear at an unexpected location An oxidized connector a connector screw not tightened properly a bad solder joint Any place with some resistance becomes important Thermistor Inputs The analog inputs are used for thermistors that measure the temperature of the temperature controlled devices often the heated build platform HPB or bed and up to two extruder s NC router specific I O view A router will use the stepper signals and limit switches just like a 3D printer The power outputs and analog inputs are free to use for other purposes T careful and don t use a finger as that may cause shorts version 1 4 2 27 02 14 page 13 BeBoPr User Manual Software The BeBoPr can be used with all BeagleBone versions The classic white and the BeagleBone Black are both hardware compatible with the BeBoPr The BeBoPr cape s on board EEPROM holds configuration information for both the 3 2 kernel I O multiplexer settings and the device tree based 3 8 kernels The board identifies itself as cape bebopr brdg Linux operating system BeagleBone classic The first BeagleBone used kernel 3 2 This kernel used information from the EEPROM on the BeBoPr to configure the 1 0 properly The 3 8 kernel used for the BBB will also work on this BeagleBone BeagleBone Black The BBB uses device tree overlays to configure the processor s
10. side of the board several small configuration jumpers can be found A soldering iron is required to apply some tin that shorts closes the jumper Alternatively a bit of conductive glue can be used Overview of the configuration jumpers and their purpose JP1 JP2 JP3 JP4 default state open When closed this will write protect the on board EEPROM This will prevent the board configuration and stepper code from being overwritten inadvertently default state open When closed the Emergency Stop input will be edge sensitive latching When open the input is level sensitive default state open When closed pin 16 of J5 will connect directly to BeagleBone pin gpio This is intended for operation with the Pepper stepper driver board only default state open When closed 5 Volt power is connected to J5 pin 2 This is intended for operation with the Pepper stepper driver board only N oon oon con con con B Z 2 X X e a D gt o e e u e P8 e e econ 0000000000000 0000000000 LE e Illustration 13 Solder jumpers on bottom side of board version 1 4 2 27 02 14 page 35 BeBoPr User Manual I2C and Emergency Stop The BeBoPr has A new connector that was not on the older boards 122
11. the BeagleBone is running a suitable kernel and the device tree overlay was loaded successfully This procedure can always be used as a first test to diagnose problems T The only exception being serial console cable Connect that to the BeagleBone if available to follow the boot process and ease debugging t Don t worry even shorting the wrong two pins on these connectors will not harm the board version 1 4 2 27 02 14 page 6 BeBoPr User Manual The Third Generation This chapter summarizes the differences between the original BeBoPr and the BeBoPr It contains useful information for users that already own a BeBoPr or are otherwise familiar with the BeBoPr specifications Illustration 1 BeBoPr R1 prototype What has changed Board layout The BeBoPr has gotten a complete new board layout All SMD components were moved from the bottom side to the top side There are no longer components underneath the board reducing the overall board height and manufacturing costs The choice of components makes it no longer possible to solder the board only a soldering iron As the board was never officially offered as DIY kit this shouldn t be an issue Elevated BeagleBone mounting With the BeBoPr Bridge the distance between the BeagleBone and the BeBoPr was increased This allowed access to the serial console connector on the BeagleBone as well as the USB host version 1 4 2 27 02 14 page 7 BeBoPr User Manual port
12. 1 0 subsystem The proper overlay is selected by configuration information in the EEPROM on the BeBoPr The BeagleBone Black needs kernel 3 8 or later 3D printer software Open source BeBoPr code An open source code repository to build a 3D printer with the BeBoPr is available at https github com modmaker BeBoPr This code uses one of the PRU coprocessors for the step pulse generation and can freely be changed PRU stepper code Each BeBoPr comes with a license for use of the PRUSS stepper driver firmware This stepper driver is proprietary code that runs on a PRU co processor and is stored in the BeBoPr s on board EEPROM The driver handles deterministic and accurate timing of the stepper pulses for all four axes simultaneously It also generates the acceleration and deceleration ramps the custom applications can easily generate accurate stepper T The API can be found in the open source BeBoPr code version 1 4 2 27 02 14 page 14 BeBoPr User Manual motor control without needing extra hardware or highly specialized real time code LinuxCNC LinuxCNC has been around for a long time Originally Intel X86 only was developed to control mills lathes and routers Since the port to the BeagleBone its also being used for 3D printers Both orthogonal XYZ types and Kossel style delta printers As an alternative for the BeBoPr code open source purists will probably like LinuxCNC more It has support for the B
13. 1 status LED yellow PWMO LED fed D16 PWMO LED fed 017 PWMO LED fed D18 power LED green D19 pe gaidos 3 Illustration 11 LEDs on the BeBoPr version 1 4 2 27 02 14 page 31 BeBoPr User Manual Power LEDs Both power LEDs see illustration 11 are green LEDs The first LED 019 in will light if the BeBoPr receives power via the board s power connector The LED will not light if the fuse F1 in illustration 12 is blown Power LED D20 in Illustration 11 indicates that the BeagleBone is turned on Status LEDs Status LEDs are either red or yellow LEDs A yellow LED D21 status in illustration 11 is available for general use It is connected to 9pio32 The default configuration will make this LED blink with the BeagleBone s heartbeat signal A red LED D24 E stop in illustration 11 turns on when the the emergency stop has been activated The red LED D23 in illustration 11 is on when the BeBoPr s input and output signals are enabled active Input signal LEDs A yellow LEDs next to each limit switch connector indicates the state of the input If there is a low impedance connection between the input pin 2 and ground pin 3 the LED turns on Output signal LEDs Each PWM power output has a red LED next to the connector The LED turns on when the output is active version 1 4 2 27 02 14 page 32 BeBoPr User Manual Switches SW6 E mode SW5 Z mode SW4 Y mode fus
14. BEBOP USER MANUAL Copyright AES allround embedded services 2012 2014 Author Bas Laarhoven Version 1 4 2 Date 28 February 2014 BeBoPr User Manual Disclaimer Warranties and Liability Disclaimer UNLESS OTHERWISE MUTUALLY AGREED TO BY THE PARTIES IN WRITING LICENSOR OFFERS THE PRODUCT AS IS AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE PRODUCT EXPRESS IMPLIED STATUTORY OR OTHERWISE INCLUDING WITHOUT LIMITATION WARRANTIES OF TITLE MERCHANTIBILITY FITNESS FOR A PARTICULAR PURPOSE NONINFRINGEMENT OR THE ABSENCE OF LATENT OR OTHER DEFECTS ACCURACY OR THE PRESENCE OF ABSENCE OF ERRORS WHETHER OR NOT DISCOVERABLE SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OF IMPLIED WARRANTIES SO SUCH EXCLUSION MAY NOT APPLY TO YOU Warranties THERE IS NO WARRANTY FOR THIS DESIGN TO THE EXTENT PERMITTED BY APPLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE DESIGN AS IS WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE DESIGN IS WITH YOU SHOULD THE DESIGN PROVE DEFECTIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR CORRECTION Limitation on Liability EXCEPT TO THE EXTENT REQUIRED BY APPLICABLE LAW IN NO EVENT WILL LICENSOR BE LIAB
15. Bone sits on top of the cape instead of the other way around The cape has four mounting holes for attachment to a flat version 1 4 2 27 02 14 page 17 BeBoPr User Manual surface Spacers with a minimum height of 4 mm are needed to prevent shorting pins on the bottom side of the cape Although BeagleBone and its capes are designed to form a stack of undetermined height there can only be a single BeBoPr and a single BeagleBone in the stack The BeagleBone is always the first board of a stack and the BeBoPr cape is always the last because neither board has stack through connectors Other capes can be stacked between the BeBoPr and the BeagleBone but not all combinations will work properly This depends on the signals used by the other capes version 1 4 2 27 02 14 page 18 BeBoPr User Manual Connections Power Connections J18 Stepper driver power Connect a 12 24 Volt DC 10 regulated power supply Can be left unconnected if no Pololu like stepper drivers modules are used J20 Board power Connect a 12 24 Volt DC regulated power supply This is the supply for the BeagleBone and the high power PWM outputs Both connectors have the ground on pin 1 and the supply plus on pin 2 8 LER AAS dedit r is H 5 E E 4 m 7 Illustration 4 BeBoPr cape connectors version 1 4 2 27 02 14 page 19 BeBoPr User Manual WARNING Do not exceed the maximum specified c
16. HDMI connector and uSD card slot while mounted on the BeBoPr This feature was propagated into the design of the BeBoPr Extended pin header connectors create a similar gap between BeBoPr and BeagleBone Wide input power range The step down converter has been re designed to operate from a DC supply voltage in the range from 12 to 24 Volts It s still using the same proven step down converter as before but some of the components have changed so that it now can operate at 24 Volts too More power for heaters Since the input supply voltage is also used for the heater outputs these can now generate more heat power without exceeding the maximum allowed currents The input power connector has also been replaced by a type that allows 16A instead of 12A of continuous current Now it is possible to control a heated build platform and an extruder simultaneously without exceeding the maximum current specifications Single fuse The expensive and hard to get SMD fuses on the three PWM outputs have been replaced by a single 5x20 mm fuse This fuse is now placed into the board s input power line Input power LED A green LED located near the input power connector indicates the presence of supply power It will not light if the fuse has blown This LED replaces the three green LEDs I2C connector The BeagleBone s I2C2 bus is now routed to 4 pin connector no need to solder wires directly to the board any more This allows I O expansion or
17. LE TO YOU ON ANY LEGAL THEORY FOR ANY SPECIAL INCIDENTAL CONSEQUENTIAL PUNITIVE OR EXEMPLARY DAMAGES ARISING OUT OF THE USE OF THIS PRODUCT EVEN IF LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES Beware Just like the BeagleBone itself this BeBoPr expansion board may be totally unsuitable for any purpose Only use it if you fully understand the risks involved and have taken proper measures to prevent personal injury and or material damage version 1 4 2 27 02 14 page 2 BeBoPr User Manual Table Of Contents Disclaimer Warranties and z DisclaiME ESE 2 Warranties qe 2 Limitation on Liability ERR KE 2 Table OFCONTENTS 2 2 FORT dS 3 o ee ceret 5 Getting 5 6 The Third Generation 7 What changed ETT 7 What did norichange s o KEEN 10 BOeBoPETE lt 11 Generic 1 Ru s 11 3D printer specific 170 VIEW Xa RTI RUE 12 NC route
18. R E ERU 35 I2C and Emergency been Base aces RET V ool e A 36 Emergency Stop InpUE ERR RR EET PRESE UAR Ka cen FERA 36 BUS X H 36 Specifications preliminary sisi ven nh ee nb RERO ES ERN A VEA AR VERI NEUEM ES 37 CONMECUONS uos cem DIVER Ld a uu bed REC E vi UL ca mtu Late 38 Mating O 40 l O Cong c erede a dv ER REC weary Vir EN dine yv EUER RE 40 Power connectofs vue vv vere ase eae 41 Troubleshooting cus oor chio iu det etae Va Toa Vra datis eiue 42 MH 43 Boald dimebsioris so pe ir dira cene eai ee ON er M tee PEU aM 44 version 1 4 2 27 02 14 page 4 BeBoPr User Manual Introduction The BeBoPr is the third generation of BeBoPr boards It integrates the original classic BeBoPr and the Bridge that was necessary to use the BeBoPr with the BeagleBone Black By integrating the Bridge the BeBoPr stays compatible with both the original BeagleBone and the BeagleBone Black It also reduces complexity and manufacturing costs This manual tries to provide all informat
19. age of the AM335X ADC Illustration 7 Analogue Input T Some driver problems have been identified but there s probably also a hardware problem The original BeagleBone had a lot of noise on the conversion results with the BeagleBone Black the situation became worse Conversion results seem to suffer from large delays irregular failure and some kind of cross talk version 1 4 2 27 02 14 page 25 BeBoPr User Manual Protection The pair of Schottky diodes D2 in combination with the 470 Ohm resistor protect the ADC input against over voltage caused by ESD or shorts to the supply Scaling The reference voltage is feeding a voltage divider that has the thermistor in the lower section and a 2k05 resistor in the upper part The thermistor is wired parallel with the voltage divider that feeds the ADC inputs The ADC measures half more exactly 0 4885 times the voltage present over the thermistor TSCADC As the PWR_THRMO voltage is twice the reference used by the BeagleBone s ADC the ADC returns the voltage divider ratio directly rather than a voltage ADS1015 The ADS1015 converter has programmable gain and differential inputs Normally this device would be configured for single ended operation over a 0 2 048 Volt range resulting in 1 mV resolution Voltage inputs Instead of using thermistors on the analogue inputs it is also possible to measure voltages directly Depending o
20. arly distinguishable Note 1 The IO enable must be active before the inputs signals can be seen by the BeagleBone Note 2 The level shifter is inverting the input signal so a low input signal will activate the LED and read back as 1 on the BeagleBone gpio input PWM analogue outputs J2 PWMO BeagleBone ehrpwm2B J3 PWM1 BeagleBone ehrpwm2A 4 PWM2 BeagleBone ehrpwm1A version 1 4 2 27 02 14 page 21 BeBoPr User Manual PWM Power Outputs Output stages The PWM outputs on the BeBoPr can be configured in software to operate at up to very high frequencies 100 kHz PWM at 10 A is possible but this will generate a lot of EMI and some dissipation in the FETs It s advisable to use a more conservative frequency to reduce the amount of heat and EMI generated The MOSFET output stages are shown in illustration 5 The fused 12 24 Volt power comes in at the top connection On the right side the wires go to the three output connectors The wires on the left side connect to the push pull MOSFET drivers used to drive the gates The third bottom output is the 10A HBP bed output and it has two FETs in parallel to reduce the dissipation Im IET 4 Illustration 5 PWM output stages Illustration 6 shows a thermal picture of the BeBoPr HBP bed output when feeding a 10A load at 40 kHz 98 duty cycle Most heat is being dissipated in the fuse on
21. at sink Both Aavid Thermaloy and Fisher have clip on heat sinks Aavid series 5768 and Fisher FK237 and FK240 will fit These can handle around 2 4 Watts depending on type and more with some forced air flow AAVID THERMALLOY 576802B00000G HEAT SINK FOR TO 220 FISCHER ELEKTRONIK FK 237 SA 220 O HEAT SINK TO 220 version 1 4 2 27 02 14 page 24 BeBoPr User Manual Analogue inputs The AM335x processor has an integrated Analog to Digital Converter that can be used as touch screen controller and as general purpose ADC This converter is called the TSCADC hereafter Because of erratic behaviour of this converter with the 3 2 kernel the original BeBoPr had the option to mount an extra ADC for more accurate results With the BeagleBone black and the 3 8 kernel performance even got got worse so the the extra 12 bit converter is now standard on the BeBoPr boards until a software solution is found This converter is called the ADS1015 Both ADCs operate in parallel on the same signals and either one can be used for the application Signal Conditioning Some signal conditioning is done before feeding the analogue signal to the ADCs For a proper understanding of the transfer function the input circuit of the first thermistor is shown drawn in illustration 7 The same circuit is available on all analogue inputs VCLAMP and PWR are low impedance sources VCLAMP is 3 4 Volts and THRMO is twice the reference volt
22. connection of a simple I2C LCD A level shifter allows connection of 3 3 or 5 Volt powered devices without chance of damaging the BeagleBone Emergency Stop input The BeBoPr now also has a hardware emergency stop ESTOP input Activation of the ESTOP signal negates the 1 0 enable without depending on the software The ESTOP immediately disables the PWM outputs and stepper signals A red LED signals the ESTOP state If preferred the ESTOP signal can be configured to latch remain active once asserted until it s cleared by software negation of the 1 0 enable signal Closing a jumper the BeBoPr activates the latch The ESTOP signal should connect to a normally closed contact or some open collector open drain type sensor When not used a jumper or piece of wire can replace the sensor An external opto coupler isolator can be used to interface to 24 Volt signals version 1 4 2 27 02 14 page 8 BeBoPr User Manual Improved PWM outputs The PWM output stages have been redesigned to generate less heat in the output switches FETs and allow up to 32 kHz PWM switching frequency without significant losses The T0220 FETs have been replaced by SMD parts with lower Roson The heated bed output now can deliver 120 Watt 10 A at 12 Volt or up to 200 Watt 8 A at 24 Volt Most heated build platform can now connect without the need for an external mechanical or solid state relay All PWM outputs now have on board free wheeling dio
23. des as described in the section named PWM analogue outputs These diodes protect the FETs and the rest of the board from the voltage spikes that occur when switching at high speed or with inductive loads I O enable LED This LED indicates that the 1 0 devices are live An inadvertently de activated 1 0 enable will prevent the I O signals to function properly This was not always obvious and hard to debug now this signal s state is directly visible Larger bypass capacitor for stepper modules The bulk capacitance that bypasses the stepper motors power supply has been increased A high quality 220 uF 50V electrolytic capacitor has been added This should prevent damage to the Pololu stepper driver modules caused from over voltage spikes generated by the motors Reset button The location of the reset button was moved to the opposite side of the board It s now situated next to the power button beneath the power jack on the BeagleBone Sensor power The 5 Volts on the limit sensor input connectors is no longer controlled by the BeagleBone but available as soon as board input power is present This supply can be used for many limit switches that need a supply to function e g optical sensors or three wire industrial proximity sensors or special functions that need 5 Volt when the BeagleBone is not present or has been powered down t For EMC reasons it may still be necessary to mount an anti parallel free wheeling diode d
24. e F1 SW3 un un 5 _ N 5 5 i 8 2 Illustration 12 Fuses and switches The BeBoPr has two push button switches that connect directly to the BeagleBone SW1 is used to control the BeagleBone s power state Push this button for several seconds until the BeagleBone turns off Push it again to turn the BeagleBone on again SW2 is used to hard reset the BeagleBone Note that this is not the same as a power on reset Switches SW3 up to SW6 connect to the stepper modules and are used to configure the stepper mode micro stepping setting Refer to the module documentation The switch number corresponds to the MS signal and the on position generates a logic high on the corresponding signal version 1 4 2 27 02 14 page 33 BeBoPr User Manual Fuses The BeBoPr has a thermal PTC type fuse F4 on board that limits the current supplied to the switches or sensors be connected to J9 J14 In case of a short circuit the current will be reduced to less than 300 mA and after removal of the short operation will be back to normal The power that is connected to J20 is fused by a single fuse F1 on illustration 12 This fuse protects the BeBoPr against short circuits on the PWM outputs and will also blow on long term overload conditions Replace the fuse only by an identical type Schurter SPT 10A HT ceram fuse time lag nr 0001 2514 version 1 4 2 27 02 14 page 34 BeBoPr User Manual Jumpers On the back
25. eBoPr since the original first BeBoPr and all software including the PRU stepper code is open source As a community effort it evolves faster than the BeBoPr 3D printer code Other NC Applications What has been written about 3D printer software above also applies for other numerical control applications Being it a simple router a laser engraver or another dedicated machine These applications will probably not need the PWM heater outputs from the BeBoPr But often they need to control devices like a spindle coolant fluid pump or laser power supply These can then be controlled from the otherwise unused outputs Unlike 3D printers and small routers a real mill or big router will require more powerful stepper motors than will fit on the BeBoPr In that case instead of using the Pololu kind of plug in stepper modules off board power stepper drivers can be used This way LinuxCNC can control up to 5 axis that connect via a flat cable to the BeBoPr version 1 4 2 27 02 14 page 15 BeBoPr User Manual The Cape Pinheader with stepper signals e g TB6560 board Rees User LED 4 Power LED 3 EC peel Reset switch Standby switch USB slave port on BeagleBone Ethernet Analog inputs on BeagleBone 4 EG vite ae t 5 Digital inputs 6x PWM power outputs 3x 12V system power Input state LED 6x with 2 status LEDs each input Illustration 2 BeBoPr
26. g the Pololu or StepStick driver modules in the sockets the DIP switches should be set for the proper micro stepping options Refer to the stepper module s documentation for the proper settings The numbers on the switches correspond with the MS input signals of the modules The position of a switch makes the corresponding signal high 1 in the off position the signal is set low 0 Take care to orient the modules properly as there are no provisions to prevent improper orientation Inserting a module backwards will destroy the module and may damage the rest of the hardware Refer to the photos in this document for the proper orientation illustration 9 shows a single stepper module inserted in the Z axis socket Often the signal names can be found printed on the board The st e p ena ble and dir ection signals should face the BeagleBone The side with the stepper motor output signals should face the stepper motor connector on the edge of the BeBoPr cape Do not orient on the location of the current limit trimmer depending on the stepper module type it s location it may be on either side of the board H3 BBY a 1 see 4 lt see cn Pt Seine PP sere Illustration 9 Z axis stepper module location Connect a proper power source regulated 12 35 Volt 10 to connector J18 Note that the stepper motors receive their power via J18 and not from J20 Impor
27. ible with built in hysteresis version 1 4 2 27 02 14 page 37 BeBoPr User Manual Connectors For each connector the pins are numbered from 1 up to the total number of pins present All connectors have a square pad on the PCB layout That pad identifies the first pin nr 1 The dual row connector J5 uses the normal header numbering scheme an even row and an odd row On the BeBoPr signal polarity is also shown on the bottom of the PCB by plus and minus symbols Pin nr Direction J2 J3 J4 PWM outputs 1 OUT Load negative terminal 2 OUT Load positive terminal Pin nr Directio J5 5 5 Pololu 4 axis mode 5 axis mode PEPPER board 1 GND 2 IN ZDISABLE 5 Volt supply 3 OUT ZSTEPPER IO SELECT 4 OUT Z ENA B DIR 5 OUT Y ENA B STP 6 OUT E DIR DIR 7 OUT E SIP A_STP 8 OUT Z_DIR Z_DIR 9 OUT Z_STP Z_STP 10 OUT Y_DIR Y_DIR 11 OUT Y_STP Y_STP 12 OUT X_DIR X_DIR 13 OUT X_STP X_STP 14 OUT ENA2 15 OUT X_ENA ENA1 16 IN Do not connect SPI_IN T This pin acts as disable input with on board pull up active low when JP4 is left open See 1 0 enable description on page 30 t For the PEPPER add on module JP4 must be closed and 5 Volt 30 mA max is supply on this pin JP3 should only be closed when attaching a PEPPER stepper driver board to J5 This signal connects directly to the BeagleBone 3 3
28. ion necessary to install operate and troubleshoot the BeBoPr This manual is still work in progress Partly the content may still refer to the original BeBoPr and may not be applicable on the BeBoPr Please do not hesitate to report errors and or send other constructive feedback to the author bas aeselectronics nl version 1 4 2 27 02 14 page 5 BeBoPr User Manual Getting Started Although the BeBoPr may seem to have an overwhelming number of connectors one can start with only a power supply and a BeagleBone attached This way some of the functionality can be tested to get familiar with the board and before integrating it into the final configuration Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 First get a BeagleBone that has been working before so that you don t run into USB or networking configuration issues Don t connect any cables or other capes to the BeagleBone If the BeagleBone was powered from the USB cable previously do not connect that cable to the BeagleBone yet Find a DC power supply that can deliver at around 1 Ampere or 10 Watt at some voltage in the range from 12 to 24 Volts Even a car battery might do for now If not done so already prepare a power cable that connects to your supply on one side and attach a power plug see Power connectors on page 41 to the other side of that cable Make sure that the negative pole of the supply connects to pi
29. irectly on the load version 1 4 2 27 02 14 page 9 BeBoPr User Manual What did not change Dimensions The board dimensions and mounting hole pattern have remained the same Connectors All connectors have remained the same and are compatible with the original BeBoPr connectors The locations on the board haven t changed either making the BeBoPr plug in replacement for BeBoPr boards or BeBoPr with Bridge combinations The new connectors for the I2C bus and the ESTOP input are located between the reset button and the stepper motor power connector beneath the RJ45 connector of the BeagleBone Software Compatibility The hardware is backwards compatible with the BeBoPr and BeBoPr with Bridge No software changes should be necessary to operate a BeBoPr with the software designed for a BeBoPr or BeBoPr with Bridge T When using the extra current that the BeBoPr can deliver compared to the BeBoPr and BeBoPr boards the power plugs and wiring should to be changed to handle the extra current Read more on this subject in Mating Connectors on page 40 version 1 4 2 27 02 14 page 10 BeBoPr User Manual BeBoPr Features Although designed as 3D printer controller the BeBoPr can be used for many other applications This chapter describes the interfaces in a generic way first followed by mapping these features on 3D printer hardware Generic I O view Analogue inputs 3x Three analogue inputs accep
30. n 1 of the connector on the BeBoPr Take the BeBoPr and only connect the power cable Do not install the BeagleBone yet Now turn the supply on Only the green LED close to the power connector should light Use a small screwdriver or some other metallic object to short two adjacent pins on one of the limit switch connectors Shorting the left pin pin 1 to the middle pin should light the yellow LED next to the connector This step verifies that the step down voltage converter on the BeBoPr is working A voltmeter should measure 5 00 0 05 Volts on the outer two pins of each limit switch connector Now turn the power off wait one minute and then attach the BeagleBone to the BeBoPr Take note of the orientation and make sure all of the pins of the header connectors on the BeBoPr are inserted in the connectors on the BeagleBone Start by aligning the BeagleBone onto the pins before applying pressure to engage the connectors Have a look from all sides and make sure all pins are inserted Be gentle Now turn the supply on again Immediately the two green LEDs on the BeBoPr should light as well as some of the blue LEDs on the BeagleBone You can now connect a network cable or USB cable Wait for the BeagleBone to boot Use the console cable if available to view the boot process Shortly after Linux has started the yellow status LED on the BeBoPr should start blinking synchronously with the heartbeat LED on the BeagleBone At this point
31. n the internal resistance of the source it may be necessary to remove the 2k05 resistors for best results R22 in illustration 7 R28 and R34 for the other inputs Thermistor curve The analogue input circuit is optimized for the widely used Epcos B57560G104F glass bead or a similar 100 thermistor The curve slope is positioned to give best resolution over the entire 25 to 250 degrees Celsius operating range The thermistor can be connected directly to the two pins of the analogue input connector It will withstand up to 12 Volts on the signal side pin 1 without damage to the BeagleBone This may happen during an accidental short circuit of a thermistor wire to a supply or heater wire t As long as the input voltage is within range and not being clipped by the over voltage protection version 1 4 2 27 02 14 page 26 BeBoPr User Manual 1 800 1 600 Vadc 1 400 1 200 1 000 ain 0 800 0 600 0 400 0 200 0 000 100 50 0 50 100 150 200 250 300 350 degrees Celcius Illustration 8 Epcos B57560G104F 100k thermistor transfer function With the component used on the BeBoPr a 100k thermistor is probably the best choice For each new thermistor a similar calculation will be necessary This curve will then be used by the application to determine the temperature that corresponds to a given analogue input value version 1 4 2 27 02 14 page 27 BeBoPr User Manual Plug in stepper drivers Before insertin
32. nfo 4 Charles Steinkuehler maintains an excellent blog about his MachineKit effort at this place http blog machinekit io p machinekit 16 html 5 If you re going to run LinuxCNC watch ntp newsgroups emc users and emc developers or register for the mailing lists version 1 4 2 27 02 14 page 43 BeBoPr User Manual Board dimensions The sketch beneath shows the board dimensions and the positions of the four mounting holes at the corners of the board All dimensions are in mm Illustration 18 Board dimensions T The drawing above if from the original BeBoPr and BeBoPr The BeBoPr board has the same dimensions and identical mounting hole spacing The outline and other holes shown on the drawing differ version 1 4 2 27 02 14 page 44
33. oard will accept many different female counter parts either polarized or not The official mating parts are from MOLEX type KK series 6471 The 1 0 connectors required for a complete board are specified in the table below Count Partno Brand Description 4 22 01 2025 Molex Crimp housing 2 54mm 2 way 6 22 01 2035 Molex Crimp housing 2 54mm 3 way 5 22 01 2045 Molex Crimp housing 2 54mm 4 way 46 08 50 0032 Molex Crimp contact tin 22 30AWG Illustration 14 connector housing Illustration 15 crimp contacts Officially these connectors require special and very expensive tooling to attach the contacts to wires If you don t have to manufacture hundreds of wires daily and according to industrial norms it is also possible to solder the wires to the contacts Illustration 18 shows a relatively cheap crimp tool that s being sold online Search on YouTube for instructions on how to attach the contacts without special tooling version 1 4 2 27 02 14 page 40 BeBoPr User Manual Illustration 16 HT 225D crimping tool Power connectors Both power inputs on the BeBoPr board power stepper power use the same type of connector A 5 08 mm pitch plug that mates the pins the BeBoPr Illustration 17 power connector Warning Because the BeBoPr board has higher current ratings for the PWM outputs than the previous BeBoPr versions a mating power connector with corresponding higher current
34. r specific 1 cseeese see seexovesesheseseezesxkeue ve EuErAROSETR RC EE VEN eE EU 13 BOTW Ae ces ocu ak NEP so aon 14 LINUX operating SYSCEIN isses ons a E ER 14 3D printer SDIEWAFB 14 LiINUXCNC 15 Other ING ADBIICALIODS oos VOR CHE px 15 WMG Gape 16 ew 16 Configuration EEPROM sssssesssssossossossossoseossoseoseoseososeseosescsesroseseseseeseseeeo 16 Daushter MOd UlES UR REEROUU T cea nde RPM Ex eR DR QM Du eben tad Kd ag ER EVE 17 CONNECUONG REDIT 19 Power CONNECTIONS UE ERRAT FEX 19 Stepper Motor CONNECTIONS 032s usee vos RE PY 20 Stepper signals Connector da E RD 20 Thermistor colla DES ped EXER ine 21 Limit switcli conlectors 21 PWM analogue E nter CRM ER ERE SINE 21 PWM Power OUELDIS E ER
35. rating was selected Connector manufacturs often only guarantee their products if you don t mix brands for two mating connectors In most cases this is not an issue but at the high currents used in this design every 4 mQ of resistance in the connection will generate a full Watt of power being dissipated in the connectors Although many of these connectors look similar they may differ in quality and materials used Only the connector specified below should be used with the BeBoPr Other connectors may mechanically fit but will require proper electrical de rating i e a reduction of the permitted current Only go this way if you re have sufficient knowledge and understand the risks involved Count Description 2 691 351 500 002 Wurth Serie 351 5 08mm Vertical WR TBL T When running at the board s rated 16A current version 1 4 2 27 02 14 page 41 BeBoPr User Manual Troubleshooting T B D version 1 4 2 27 02 14 page 42 BeBoPr User Manual References 1 main source of information is https github com modmaker BeBoPr It contains the open source code for the Mendel 3D printer port 2 sure to read and watch the wiki pages at https github com modmaker BeBoPr wiki for new information These may contain more up to date information and other useful links 3 For on line help and other links don t forget to visit and register at the BeBoPr forum http forum bebopr i
36. stop is not required or during set up and testing I2C Bus The BeagleBone s I2C bus that also connects to the cape s EEPROM and AD converter is connected to the first four pins of J22 J22A A bi directional level shifter converts the BeagleBone s 3 3 Volt bus to the levels used on the external bus and isolates the bus if the external device is powered downt The supply voltage used by the external device s has to be connected to the I2C connector as reference Any voltage in the range 3 3 up to 5 0 Volts can be used for the external devices An external device requiring only a several tens of milli Amperes at 5 0 Volts could take this supply from one of the limit sensor supply pins This way no additional external supply is needed and in many situations not all inputs will be used leaving a connector with supply pin free to use T The BeBoPr board comes with a red jumper installed on J22B t If this wasn t done the I2C bus would hang and the BeagleBone wouldn t be able to detect the cape properly once the external device has no power version 1 4 2 27 02 14 page 36 BeBoPr User Manual Specifications preliminary Board Power input J20 min 10 8 Volt max 26 4 Volt Stepper Power input J18 max 35 Volt see text Board Power consumption via J20 BeBoPr only no external connections T B D BeBoPr with BeagleBone and no external connections T B D Step down converter efficiency T B D The combined current drawn via
37. t a 0 3 6 Volt input range The inputs are protected against over voltage Accidental shorts between thermistor wires and the 12 Volt supply voltage will not destroy the BeagleBone The input filter scales by a factor 0 5 and limits the analogue input signals to the BeagleBone s 0 1 8 Volt range Instead of using the troublesome BeagleBone s on chip ADC a more stable 12 bit ADS1015 is present on the BeBoPr It operates in parallel to the BeagleBone s ADC and uses a standard Linux driver Analogue PWM outputs 3x Three high power outputs are connected to the processor s PWM devices These outputs can also be used as digital outputs to control a relay a motor or other DC load Digital inputs 6x Six digital inputs can be used for simple logic signals or to connect switches or opto sensors directly The three pin connectors also provide a 5 Volt signal for sensors that need a supply voltage The supply is protected against short circuits by a thermal fuse Digital outputs 12x Twelve 5 Volt TTL CMOS level compatible outputs are available on a header connector These outputs can be switched to tristate via software and by an active low disable signal Supply The board can operate from a single power supply that provides a DC voltage in the range 12 to 24 Volts If required the stepper drivers can operate from a different supply than that is used for the board An efficient step down converter generates the 5 Volt suppl
38. tant Pololu modules can be damaged by the back feed from the motors On the Pololu site the following warning can be found version 1 4 2 27 02 14 page 28 BeBoPr User Manual Warning This carrier board uses low ESR ceramic capacitors which makes it susceptible to destructive LC voltage spikes especially when using power leads longer than a few inches Under the right conditions these spikes can exceed the 45 V maximum voltage rating for the DRV8825 and permanently damage the board even when the motor supply voltage is as low as 12 V One way to protect the driver from such spikes is to put a large at least 47 pF electrolytic capacitor across motor power VMOT and ground somewhere close to the board For the original BeBoPr boards it was recommended to mount some extra bulk capacitance over the input pins of J18 as shown in illustration 10 Use good quality capacitor to handle these recurring current peaks 470 35 Nichicon nr UPW1V471MPD has proven to work at stepper voltages up to 24 Volts A smaller capacity will do but don t lower the working voltage The BeBoPr has a single 220uF electrolytic and two 10uF ceramic capacitors on board So no external capacitor should be needed Illustration 10 Extra capacitor to protect Pololu modules version 1 4 2 27 02 14 page 29 BeBoPr User Manual I O enable To prevent 1 0 conflicts and glitches on stepper or power outputs during initializa
39. the right The free wheeling diode in the center of the top image just between the rightmost FET and the output connector is also getting a little warmer than the FETs version 1 4 2 27 02 14 page 22 BeBoPr User Manual Illustration 6 Temperature profile 10A PWM Free wheeling diodes If an inductive load is installed a free wheeling diode should be used A simple silicon rectifier diode of type 1N4007 or compatible will do in some situations in other cases a fast recovery type will be better It reduces the EMI and protects the BeBoPr and BeagleBone from voltage spikes Place this diode as close to the load as possible or as a last resort mount it together with the wires of the load at the output connector Connect the diode anti parallel to the load i e connect the or Anode to the negative output terminal and the or Cathode to the positive output terminal Power dissipation Most of this section is not applicable for the BeBoPr because of changes to that part of the design As the information herein is still correct and applies to BeBoPr boards with TO 220 FETS this section has not been removed version 1 4 2 27 02 14 page 23 BeBoPr User Manual Some example calculations to show the effect of large currents The dissipation power lost in the FET roughly depends on three factors The current through the FET the switching frequency and the temperature of the FET Using the FET to switch mainly resistive
40. tion the inputs and outputs are isolated from the BeagleBone during start up Once the BeagleBone has booted it is the responsibility of the user application to initialize the outputs to safe values before enabling the 1 0 Enabling the 1 0 is done by by setting an signal appropriately gpio66 must be configured as output and set to a logic This activates a circuit that enables the level shifters for the inputs and buffers for the outputs On the BeBoPr the 1 0 enable signal is also to the Emergency Stop circuit ESTOP must be negated before 1 0 enable can be activated via gpio66 The BeBoPr has a red LED 023 marked IOE that turns on if the 1 0 enable signal is active Another override is via pin 2 on J5 If this pin is pulled low all stepper driver outputs are disabled tri stated This feature can be used to prevent overloading the stepper outputs when external stepper drivers with a separate power source are being used Depending on the type of inputs used these inputs may form a short circuit for the stepper drivers while the supply is turned off In that case connect the driver s logic supply to pin 2 on J5 to disable the BeBoPr outputs while the drivers are turned off version 1 4 2 27 02 14 page 30 BeBoPr User Manual Indicator LEDs 06 XmaxLeED yellow D7 XminLED yellow 08 YmaxLED ydlow D9 Ymin LED yellow D10 Zmax LED yellow D11 Zmin LED yellow 023 Wenabke LED red D20 power LED green D2
41. urrent for these connectors WARNING Do not connect power to the DC INPUT P5 jack on the BeagleBone once mounted on the BeBoPr This will most likely damage the BeBoPr and or the supply connected to the DC INPUT Stepper Motor Connections If the BeBoPr has the stepper driver modules on board the four stepper motors connect to J15 J16 J17 and J19 In that case connector J5 is hidden underneath the driver modules and can not be used J15 X axis pins 1 amp 2 motor coil A pins 3 amp 4 motor coil B J16 Y axis pins 1 amp 2 motor coil A pins 3 amp 4 motor coil B J17 Z axis pins 1 amp 2 motor coil A pins 3 amp 4 motor coil B J19 E axis pins 1 amp 2 motor coil A pins 3 amp 4 motor coil B Stepper signals connector J5 all stepper signals are present on this connector It connects directly to the 15 pin sub D connector of a TB6560 4V5 3A stepper driver board sold on e Bay Pin nr Direction Signal AM3359 pin 1 GND 2 in out EXT VCC sense 3 out STEPPER IO SELECT 4 out Z BUF V5 5 out Y ENA BUF T4 6 out E_DIR_BUF U9 7 out E STP BUF R6 8 out Z DIR BUF R5 9 out Z STP BUF 05 10 out Y DIR BUF T3 11 out Y STP T2 12 out X DIR BUF R4 13 out X STP BUF R3 14 out E ENA BUF V9 15 out X ENA BUF 1 16 Table 1 5 stepper driver signals version 1 4 2 27 02 14 page 20 BeBoPr User Manual If the BeBoPr controls external stepper drivers the stepper motors connect directly to these
42. y for the BeagleBone This makes the BeBoPr compatible with almost any kind of DC power version 1 4 2 27 02 14 page 11 BeBoPr User Manual source Choose between a cheap ATX power supply a simple laptop 18 20 Volt adapter an adjustable lab bench supply an industrial 24 Volt supply or whatever is available and can deliver sufficient power for your application 3D printer specific I O view Stepper outputs The BeBoPr has four sockets for Pololu StepStick or compatible modules If these modules are used the motors connect to the 4 pin connectors next to the module sockets on the BeBoPr Applications requiring more powerful stepper drivers can connect these drivers to the pin header connector that is located between the Pololu sockets and that carries all relevant signals to control up to 5 axes Limit switch inputs These inputs accept a mix of mechanical switches and or optical sensors They can connect directly to slow changing input signals because of the Schmitt Trigger inputs Each input has a 5 Volt supply pin for external sensors that need power to operate This supply can deliver 0 3A for all inputs combined and is short circuit protected by a thermal fuse Power outputs Three powerful outputs can generate PWM signals for motors and or heaters or analogue signals for laser power control These outputs can be controlled directly by the high resolution PWM controllers in the AM335X processor or via GPIO signals for bit
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