The E-stop circuit is composed of four physical buttons in normally-closed configuration and a remote fork in series. With this configuration when the circuit is opened by pushing on a physical button or via the remote fork the 12v E-stop circuit is opened which at first cuts the main power source of the motor and subsequently cuts the 12v motor enable signal to shutdown the canbus modules via the LED boards relay. See bellow a simplified electrical circuit of the E-stop and the different connection to the breakout pcb.

Modifications

As a part of porting the system to Zenoh, the MCU stopped responding to the LLC, which triggered unintended behavior like constant solid red lights. To remediate the problem, the Arduino setup was added to replace the function occupied by the MCU and enhance the diagnostic experience for the user. To remove the MCU it's remaining function had to be emulated the three remaining functions being the LED commands, the estop circuit logic and the DC-DC converter startup. To emulate the later functions electrical modifications had to be made on the breakout board. As seen on the E-stop electrical diagram the Omron G6L-1F 12v relay is controled by both the Estop loop connection and the mcu. A simple bypass of this relay enables the Estop loop to manage itself without the need of the mcu booting to allow the E-stop loop to control the Sevcon motor controler. The second electrical bypass relates to the DC-DC converter the model chosen by Clearpath incorporates an enable pin that needs to be shorted to ground to allow proper operation see picture bellow for details.