Power Board v4

The SRv4 Power Board

The Power Board distributes power to the SR kit from the battery. It provides six individual general-purpose power outputs along with two low current 5V power outputs.

It also holds the internal On|Off switch for the whole robot as well as the Start button which is used to start your robot code running.

Board Diagram

Diagram of the SRv4 Power Board


There are six power output connectors on the board, labelled L0–L3, H0, and H1. These can be enabled over USB and supply around 11.1V (±15%). The “H” connectors will supply more current than the “L” connectors.

The 5V connectors can be used to connect low-current devices that take 5V inputs.

Finally, there are connectors for external Start and On|Off switches. You may connect any push-to-make latching switch for the On|Off button, or a push-to-make button for the start button.


If you intend to use only the internal On|Off switch, you must connect a CamCon to the On|Off connector with a wire connecting one pin to the other pin on the same connector.


LED Meaning Initial power-up state

Green when powered

Flashing red and green when the battery is low



5V Green when 5V is being supplied Green
H0-1, L0-3

Green when the output is on.

Red when the output’s current limit is reached

RUN|ERROR Orange on power-up, or USB reset Flashing green when ready to run Solid green when running or booting Orange

On power-up, the Power Board will emit some beeps, which are related to the version of the firmware it has installed.

If the Power Board starts beeping (and all the outputs turn off) then this means that the whole board’s current limit has been triggered.


Control Use
ON|OFF Turns the power board on, when used in conjunction with an external switch
START Intended to start the robot. The state is accessible over USB.

USB Interface

The Vendor ID is 1bda (University of Southampton) and the product ID is 0010.

The Power Board is controlled over USB by sending requests to the control endpoint.

Parameter Value
bmRequestType 0x00
bRequest 64

There are a list of ids defined in the firmware of the power board that will let you read and write values to it.

It is recommended to read the source to further understand how to control this device.

It should also be noted that as the control endpoint 0x00 is used to send data to this device, it is not actually compliant with the USB 2.0 specification.

udev Rule

If you are connecting the Power Board to a Linux computer with udev, the following rule can be added in order to access the Power Board interface without root privileges:

SUBSYSTEM=="usb", ATTRS{idVendor}=="1bda", ATTRS{idProduct}=="0010", GROUP="plugdev", MODE="0666"

It should be noted that plugdev can be changed to any Unix group of your preference.

Case Dimensions

The case measures 83x99x24mm. Don’t forget that the cables will stick out.


Parameter Value
Main battery fuse current 40A
Overall current limit 30A
High current outputs (H0-1) 20A
Low current outputs (L0-3) 10A
Main output voltage (nominal) 11.1V ± 15%
Maximum output current per 5V channel 1A


You can access the schematics and source code of the firmware for the power board in the following places. You do not need this information to use the board but it may be of interest to some people.


Some of the documentation in this section has been taken and modified from `Student Robotics`_. See here for more information.