Firmware Architecture

ECU A, B, C and D share a common architecture, with the exception that ECU A also has USB enabled. On this page, we detail the architecture of the firmware for each ECU, starting with the simpler ECU B, C, and D.

ECU B, C, and D

Firmware of ECU B, C and D contains six tasks:

  • The CAN Receive Task, which receives and processes CAN messages through a Stream Buffer filled by the CAN-FD peripheral Interrupt Service Routine (ISR).

  • The Diag RX Task, which receives and processes full (reconstructed) diagnostic messages through a Stream Buffer filled by the CAN Receive Task.

  • The main Periodic Task, which is executed periodically at a specified interval (typically, 10ms). It is responsible for updating various modules of the firmware. Periodic CAN message transmissions are requested by this task.

  • The Diag TX Task, which is responsible for fragmenting and sending diagnostic answers, with specified Flow Control settings.

  • The CAN Send Task, which is responsible for sending CAN messages requested through a Stream Buffer. Messages may be requested by any other task that needs to communicate over CAN.

  • The Error Handling Task, which is woken up when an error needs to be processed and reported.

../_images/ECUBCD_firmware_architecture.png

Architecture of firmware of ECU B, C, and D.

ECU A

Firmware of ECU A is identical to ECU B, C, and D, but with two additional tasks:

  • The USB Receive Task, which receives USB commands and processes them

  • The USB Send Task, which sends requested data (again, through a Stream Buffer) over USB.

With ECU A, diagnostic commands may also be sent over USB instead of CAN.

../_images/ECUA_firmware_architecture.png

Architecture of firmware of ECU A.

Additional Tasks

In recent versions, new tasks have been added to allow users to easily implement their custom tasks. ECU A can (optionally) use these tasks to implement a gs_usb (candlelight) device.