The switch table is the "brain" of the car, used for controlling functions like lights, wiper, brake and acceleration. It processes the inputs from the switches, steering wheel and throttle pedal then compiles them into it's state message and sends that out over CAN.

1. State Broadcasting: Sends a CAN message every 50ms about its own state (switch positions, throttle position)
2. Wiper Control: Controls the wiper's DC-DC converter and servo with PWM
3. Throttle Input: Reads and filters the analog potentiometer connected to the throttle pedal
4. Motor Control: Optionally sends throttle reference commands to the motor controller over CAN

Nucleo C092RC Development Board

• Microcontroller: STM32C092RCTx (LQFP64)
• Clock: Internal HSI oscillator running at 48MHz
• CAN Interface: FDCAN1 using the on-board CAN transceiver
• Programmer/Debugger: Nucleo built-in ST-Link

Custom board: "Switch Table v4"

• Microcontroller: STM32F412RET6 (LQFP64)
• Clock: 8MHz external crystal, HSE
• CAN Interface: CAN2 using an ESDCAN24-2BLY transceiver
• Programmer/Debugger: External ST-Link programmer

This project uses 4 types of peripherals to achive it's functionality:

The CAN2 peripheral is used for CAN communication on the pins PB12 and PB13.

The messages used are the following:

Byte 0 (STW_STATE_A):
  Bit 0: ACC (Cruise Control Activate)
  Bit 1: DRIVE (Drive Mode)
  Bit 2: REVERSE (Reverse Mode)
  Bit 3: LAP (Lap timing signal)
  Bit 4: TS_L (Traction Control Left)
  Bit 5: TS_R (Traction Control Right)
  Bit 6: FUNCTION1 (Reserved)
  Bit 7: FUNCTION2 (Reserved)

Bytes 1-3: Position of the 3 switches on the steering wheel (STW_STATE_B/C/D)

Byte 0 (VCU_STATE_A):
  Bit 0: HEADLIGHT
  Bit 1: HAZARD
  Bit 2: AUTO
  Bit 3: BRAKE
  Bit 4: LIGHTS_ENABLE
  Bit 5: MC_OW (Motor Control Override)
  Bit 6: WIPER
  Bit 7: Reserved

Byte 1 (VCU_STATE_B):
  Bit 0: RELAY_NO
  Bit 1: RELAY_NC
  Bits 2-7: Reserved

• TIM2 is used to trigger the ADC
• TIM3 is for PWM generation to the wiper, on it's CH1 output (pin PB4)
• TIM14 is the tick timer that fires every 50ms to wake up the CPU

ADC1 with IN0 on pin PA0 is used to read the throttle pedal position. It is started in DMA mode with the TIM2 timer triggering it every 5ms. It writes the conversions to the throttle_adc_buffer variable.

This is only used for debugging purposes. In the user.h file, its possible to set what debug outputs the MCU sends over UART.

This code is designed to minimize the amount of user code in generated files. The main working logic is in user.c and user.h. Another key factor is limiting power consumption, which means also limiting CPU time.

sw_table_stm32/
├── sw_table_stm32.ioc            # STM32CubeIDE pin/peripheral configuration
├── sw_table_stm32.pdf            # Auto-generated hardware pinout diagram
├── Core/
│   ├── Inc/
│   │   ├── main.h               # Generated header, contains the pin definitions
│   │   └── user.h               # User-defined functions and structures
│   ├── Src/
│   │   ├── main.c               # Main entry point and peripheral initialization
│   │   └── user.c               # User-defined functions, main controller logic

• main.c: System initialization, timer setup, interrupt handlers and main function (entry point)
• user.c: Core application logic including CAN communication, GPIO control, and throttle processing
• user.h: Data structures, function declarations and constant definitions

• Use fixed-point math instead of floating-point where possible because its faster
• Keep ISRs short: Set flags and do the actual processing in main loop
• Power efficiency is key: Try to use DMA and other hardware logic to limit CPU usage as much as possible

Created by SZEnergy Team for Shell Eco Marathon

• Váradi Marcell (varma02@GitHub)

This project is licensed under the MIT License - see the license file for details.