PiKoder/SSC-HP User`s Manual ( file)
Contents
1. Once you hit the Send 3 byte command button the bytes are sent to the PiKoder see below as per protocol definition there is no response by the SSC Pololu Serial Transmitter v1 3 Connected FEER COM Port COM4 Baud Rate bps _ append CRC7 byte use Ox prefix for hex e g you can write 128 or 0x80 single byte 2 byte command 3 byte command Send 3 byte command 4 byte command 5 byte command 6 byte command Sent Received data hex 06 49 34 sent FF 08 FE PiKoder SSC HP User s Guide ASCII Command Interface The ASCII Command Interface ACI provides access to all relevant system pa rameters All commands are simple ASCII not case sensitive and are sent using a Windows based terminal program such as Hyperterm or Tera Term The com mands can be typed in right away and the response of the controller is readable without referring to any specific code tables Please note that neither CR nor LF is needed to send the command to the controller There are two basic types of commands commands for quering parameters and for setting parameters If a parameter is read the PiKoder SSC HP will provide for proper formatting by sending a CRLF prior to sending the parameter value and support readability by sending another CRLF after the parameter value If a parameter is set th2. out value gt 0 a value of 0 would disable the timer function Com mand execution is acknowledged by the PiKoder with a Tr te query the current time out value in multiples of 0 1 s response of 000 indicates that the fail safe function is not activated 11 PiKoder SSC HP User s Guide Room for notes 12 Pin Description and Packaging The PiKoder SSC comes in an 18 pin DIP package see below The device oper ates at 5 Volts Please refer to the PIC 16F648 data sheet from Microchip www microchip com for complete electrical and physical specifications A complete description of the pins is given on the following page If a different package would be re Servo 3 Servo 1 quired for your application then please contact sales pikoder com per Servo for more information NC OSC1 MCLRIVPP osc2 For evaluating the PiKoder SSC a pcb and a complete kit is available VSS VDD at www pikoder com This kit can Servo 5 PGD make your development process more efficient and provides for R ras modularity in your design TX Servo 7 Servo 6 Servo 8 13 PiKoder SSC HP User s Guide Description of pins Pin Symbol Description 1 Servo 3 Output pin with PWM signal for servo channel 3 2 Servo 4 Output pin with PWM signal for servo channel 4 3 NC Not connected reserved for later use 4 MCLR VPP Reset pin active low Connects dir
3. PiKoder SSC HP User s Guide Version 1 0 dated 05 01 15 Gregor Schlechtriem PiKoder SSC HP User s Guide Content Overview 3 Features 5 Daisy CHADE aiser asset 5 Failsafe Positions orenera easa phat atet pit wet miata niet ate nits 5 Serial Interface 7 Mint SSC Protocole cecctvestoecivestevnicestecsteecteccsvecencses Seaside naa 7 ASCII Command Intertace sindene annen 10 Pin Description and Packaging 13 Deschipfion of PINS arasina ren 14 Standard application 15 ii Overview The PiKoder SSC HP is a single chip solution for implementing a high precision serial servo controller SSC which gives you full control of up to eight servos or electronic speed controls with a resolution of 0 2 us which is currently the best resolution available in the industry This User s Guide covers the features the programming and the serial interface of the PiKoder SSC HP You can connect e g your Arduino or Raspberry Pi without any additional inter face hardware directly to the PiKoder s UART With the addition of a simple off the shelf USB to UART adapter you control the servos directly from your com puter The PiKoder SSC HP supports two protocols MiniSSC protocol representing a very common protocol for controlling SSCs and a two way ASCH Protocol designed to support controlling the SSC HP with standard terminal programs such as but not limited to Tera Term and TTY The PiKoder SSC HP Serial Servo C
4. WM GND PWM GND PWM Servo 1 Servo 2 Servo 3 Servo 4 Servo 5 Servo 6 Servo 7 Servo 8 15
5. e PiKoder SSC HP will acknowledge the proper execution by sending an framed by CRLF If a command could not be interpreted at all then a question mark framed by CR LF would be echoed Please note that protocol syntax checking is very lim ited at this point in time All pulse widths are given in units of 0 2 us If you want to calculate the value in us then simply devide the respective value by 5 E g the neutral position of 1 500 us would be represented by a numerical value of 7 500 5 1 500 us The following ACI commands are available iP query the current pulse width for channel i i 1 8 PiKoder will re spond CR LF xxxxx CR LF with xxxxx representing the pulse width in multiples of 0 2 us set the pulse width for channel i to xxxxx 0 2 us xxxxx in dec imal format i 1 8 PiKoder will acknowledge execution of the program by sending an CR LF CR LF O query the firmware version PiKoder will respond in a format n nn framed by CR LF S will save the current parameters to the controller s EEPROM making the current servo positions the start up positions after powering up re turns a upon successful completion framed by CR LF Uir query the upper limit for pulse width for channel i PiKoder will re spond xxxxx with xxxxx representing the pulse width in multiples of 0 2 us xxxxx in decimal format i 1 8 Ui xxxxx set the upper lim
6. ectly to Vss for au tomatic reset at power up 5 VSS Supply voltage Connect to 5 V DC 6 Servo 5 Output pin with PWM signal for servo channel 5 i RX Serial receive input 8 TX Serial transmit output 9 Servo 6 Output pin with PWM signal for servo channel 6 10 Servo 8 Output pin with PWM signal for servo channel 8 11 Servo 7 Output pin with PWM signal for servo channel 7 12 PGC Clock pin for In Circuit Serial Programming 13 PGD Data pin for In Circuit Serial Programming 14 VDD Ground connection 15 OSC2 Crystal 20 MHz Please refer to Microchip documenta tion for details 16 OSC1 Crystal 20 MHz Please refer to Microchip documenta tion for details 17 Servo 2 Output pin with PWM signal for servo channel 2 18 Servo 1 Output pin with PWM signal for servo channel 1 14 Standard application The following schematic shows the standard application of the PiKoder SSC HP Plesase note that the components colored in blue are only required for In Circuit Serial Programming on your board ICSP PINs 12 RB6 PGC PIC 16F648A 13 RB7 PGD 18 RANAN 8 TX o RB2 TX CK RX o RB1 RX DT RA5 MCLR VPP 6 R1 D1 16 ik 1N4148 da RATIOSCHICLIN Controller Power o 5V JP1 Connects Controller Power to Servo power GND o Servo Power 4 8 6V amp amp 3 4 88 88 68 4 b 5 4 GND PWM GND PWM GND PWM GND PWM GND PWM GND P
7. it for pulse width for channel i to xxxxx 0 2 us xxxxx in decimal format i 1 8 PiKoder will acknowledge execution with a framed by CR LF Li query the lower limit for pulse width for channel i PiKoder will re spond xxxxx with xxxxx representing the pulse width in multiples of 0 2 us xxxxx in decimal format i 1 8 10 Li xxxxx set the lower limit for pulse width for channel i to xxxxx 0 2 us xxxxx in decimal format i 1 8 PiKoder will acknowledge execution with a framed by CR LF Ni query the pulse width for the neutral position for channel i PiKoder will respond xxxxx with xxxxx representing the pulse width in multiples of 0 2 us xxxxx in decimal format i 1 8 Ni xxxxx set the pulse width for the neutral position for channel i to xxxxx 0 2 us xxxxx in decimal format i 1 8 PiKoder will acknowledge execution with a framed by CR LF M or m query the current channel offset for the miniSSC protocol M iii or m ii set the channel offset for the miniSSC protocol Z query the current zero offset value Z ii set the zero offset T iii t iii enables the fail safe timer iii is given in multiples of 0 1 s Please note that input is always given in three decimal digits ranging from 001 0 1 s to 999 99 9 s In the factory default configuration the fail safe timer is not active You would activate the monitoring by sending a time
8. ontroller would automatically detect the pro tocol used and no user interaction would be required The PiKoder SSC HP also has non volatile EEPROM data storage for retaining application specific operating parameters such as startup position after powering up neutral position and upper as well as lower limits for servo pulse width This User s Guide is based on the most recent hard and firmware available for the PiKoder SSC HP Please check for updated information and new software releas es on www pikoder com PiKoder SSC HP User s Guide Please share with me any comments improvement ideas or errors you will find or encounter in working with your PiKoder SSC HP I can be reached at webmas ter pikoder com Thank you very much Features This section will familiarize you with some specific aspects of the feature set of the PiKoder SSC HP allowing you to customize the controller to your specific needs and requirements Daisy Chaining The PiKoder SSC does fully support the miniSSC protocol and allows you to daisy chain controllers in order to control up to 255 servos as specified in the miniSSC protocol definition The latest version of the SSC Control Center pro vides for setting a miniSSC Offset and thereby defining the channel base address the PiKoder SSC would respond to This means that the PiKoder SSC can con trol any contiguous block of eight servo numbers from 0 to 254 Please refer to www pikoder_ssc_en htm f
9. or more information and an application note detailing the setup for daisy chaining Failsafe Position The PiKoder SSC does support a failsafe position for the use in autonomous and rc applications You can activate a timer for 0 1 s to 99 9 s to monitor the commu nication If no message is received within this preset time frame then the PiKoder SSC would set all servo outputs to the neutral position If you were to use this function you might want to implement a regular ping in your application to make sure that the failsafe function is not triggered by a period of inactivity PiKoder SSC HP User s Guide Room for notes Serial Interface The PiKoder SSC HP s serial interface is based on TX and RX lines which allow the controller to sent and receive non inverted TTL 0 5V serial bytes The parameters for the serial transmission are 9600 Baud 8 data bits one stop bit with no parity The bytes sent to the PiKoder SSC HP are commands which allow you to control the program and control the SSC The PiKoder SSC HP supports two protocols MiniSSC protocol representing a very common protocol for controlling SSCs a two way ASCH Protocol designed to support controlling the SSC HP with standard terminal programs such as but not limited to TerraTerm Putty hyperterm The PiKoder SSC HP Serial Servo Controller does automatically detect the termi nal protocol no user interaction would be required Mini SSC P
10. pect to du and di e du and dl are calculated per channel and may differ per channel allowing for asymmetric ranges and a neutral positon outside of the mechanical central position of the servo e du and dl are calculated during controller startup and there is no update when you change the values of neutral upper or lower limit without reset ting the controller This means the intended operation would be to set the values reset the PiKoder SSC and then verify the setting e du and dl are calculated based on 8 bit arithmetic Depending on the num bers a slight overrun over the upper limit resp a slight underrun of the lower limit may occur For testing the miniSSC protocol you may want to use a byte oriented tool such as the Pololu Serial Transmitter utility for Windows see http www pololu com docs 0 23 for more details After installing and starting the software you would have to connect to the PiKoder SSC by selecting the COM port and pushing the connect button The miniSSC protocol is a three byte command and should be entered in the respective column as shown below Pololu Serial Transmitter v1 3 Connected Baud Rate 9500 bps append CRC byte use Ox prefix for hex e g you can write 128 or 0x80 single byte Send single byte 2 byte command 3 byte command 4 byte command Send 4 byte command 5 byte command 6 byte command Sent Received data hex
11. rotocol This protocol allows you to control up to 255 different servos by chaining multiple servo controllers together It only takes three serial bytes to set the target of one servo so this protocol is good if need to send many commands rapidly The Mini SSC protocol is to transmit OxFF as the first command byte followed by a servo number byte and then the 8 bit servo target byte for the servo position A servo target byte of 127 Ox7F will always indicate the neutral position main tained as a PiKoder SSC parameter The actual position taken by sending a servo target byte to the controller is calcu lated depending on the actual parameters If you wanted to move the servo from PiKoder SSC HP User s Guide neutral towards the upper limit then the increment in pulse length du is calculated based on du Upper Limit Neutral 127 Steps This meas for example that with an upper limit of 2008 us and a neutal position of 1500 us an increment of one in the servo target byte would result in du 2008 1500 us 127 Steps 4 us Step Therefore a servo target byte of 0x80 which is an increment of one to the neutral position would result in a pulse length of 1500 us 4 us 1504 us The same procedure is applied when you wanted to move the servo from neutral towards the lower limit then the decrement in pulse length d is calculated based on dl Neutral Lower Limit 127 Steps Please note the following with res
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