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Revision as of 16:20, 17 February 2012 by Tom (talk | contribs) (Overview)

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The SPI_Servo PCB
The SPI_Servo PCB

This is the documentation page for the SPI_servo board.


This module enables you to easily control upto 7 servomotors over an SPI interface, while needing minimal resources from your CPU. The PCB is equipped with two SPI connectors, so daisychaining multiple SPI modules is an option.
This allows you to control the LCD with only 4 data lines (MOSI, MISO, SS and SCK). This is not only pin-saving, but is is also possible do daisy-chain multiple modules (we will be releasing additional boards with other functions in the very near future)!
The board can be used with all microcontrollers, such as the Atmel AVR, Arduino/Freeduino boards, Microchip PIC, etcetera. Other computers/boards with an SPI interface (such as the Raspberry Pi) should also be able to control this module.

For small servos, the power supplied by the SPI connector is enough. For larger servos however, the voltage drop may be to high. We suggest conneting an auxillary 5V power source to the PCB, and cutting the trace connecting the servo power rail to the SPI power rail. Future versions will have a jumper for this cause, and a dedicated servo power connector.

External resources


The CPU:

Additional software

Related projects


The pinout is standard for servo-motors; Pin 1 is GND (near the edge of the board) Pin 2 is VCC (5V) Pin 3 is data


The only LED is a power-LED.

Jumper settings

Solder jumper (on bottom layer): ICSP-Enable. CAUTION! Pin 1 and 2 are connected by a narrow PCB track. Cut this if you want to change this jumper setting.
1-2: Default: Both SPI connectors connected in parallel.
2-3: ICSP enabled; programming the MCU over the 6-pin connector marked SPI3 (near the edge of the board) is enabled.


To control the servos, you need to send things over the SPI bus to the PCB. The protocol is explained here.

The software

Default operation

Future hardware enhancements

  • Add extra power connector for servo power
  • Add possibility to disconnect servo-power from VCC

Future software enhancements



  • Initial public release