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20-Channel Serial Servo Controller

Posted March 15th, 2010 in Controlers, Products by Victor D


USB adapter

The COM-SRV20 servo controller is a very compact solution for controlling up to 20 radio control (RC) servos from a computer or microcontroller. The controller measures just 2.1in x 1.3in, it incorporates a 5V servo powered voltage regulator (no need for external power supply, it can provide up to 150mA power for an external microprocessor), and yet it is one of the most robust servo controllers available. Each servo range can be controlled independently, including any standard RC servos or the giant 1/4-scale servos.


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The communication protocol used is similar (compatible) with the MiniSSC II servo controller and any software written for it. The COM-SRV20 servo controller is less than half the size and price of similar servo controllers. This means that the servo controller is an ideal solution even if you need to control few or more servos. The interface to the servo controller is a standard RS-232 serial port with +/-15V levels or TTL-levels (5V or 3.3V Logic Levels), using 9600b/s baud rate.

The COM-SRV20 uses a very simple protocol(like the Mini SSC II)

    Byte 1                                       Byte 2                               Byte 3

[ sync marker “FF” (255) ]               [ servo # (0-19) ]               [ position (0-200) ]

To command a servo to a new position requires sending three bytes at the serial rate of 9600b/s baud, no parity check, and 1 stop bit (known as 9600N1).

These must be sent as individual byte values, not as text representations of numbers as you might type at a keyboard.

The Power/Activity LED on the COM-SRV20 board it lights steadily when power is applied to the board and stays on until data is received, when the data is received the LED will start blinking.



  • PCB size: 2.1″ x 1.3″ (55mm x 33mm)
  • Controls up to 20 servos
  • Serial interface (RS-232 and TTL @ 9600)
  • Data In voltage levels: 5V (TTL) or +/-15V (from RS-232 connector)
  • Accepts 3.3V Data In from 0-3.3V (Logic) Interfaces (no 3.3V to 5V conversion needed)
  • Servo type supported: Futaba, Hitec, T-pro, EXI, etc.
  • Power supply: Servo powered(min. 5V) or external power(min. 5V to 12V)
  • Servo travel range: 0 – 180°
  • Servo resolution:1uS, .09° (200 steps / 180°)
  • Low power consumption: 15mA



20 Ch Serial
Servo Controller

4 Servo Controller – Example

20 Ch Serial Servo Controller – Connections

20 Ch Serial Servo Controller – Utility



User Manual: COM-SRV20 Serial servo controller.pdf
Servo Controller Utility: SYSCONE 20-Channel Serial Servo Controller-Utility.exe