Sensors I/O

The sensors layer ties the physical inputs to the board's runtime objects. It is where the CAN-Gateway decides which sensors exist on a given variant, how they are initialized, and which periodic or interrupt-driven hooks keep them updated.

The core implementation is found in repos/CAN-Gateway/Core/Src/App/SensorsIO/sensors.c with header definitions in repos/CAN-Gateway/Core/Inc/App/SensorsIO/sensors.h.

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Compile-Time Board Variants

The same codebase compiles for both the front and rear physical PCB instances. The active variant is configured in repos/CAN-Gateway/Core/Inc/App/system_var.h by setting the DEVICE_TYPE preprocessor macro:

#define DEVICE_FRONT_GATEWAY 1
#define DEVICE_REAR_GATEWAY  2
#define DEVICE_TYPE DEVICE_FRONT_GATEWAY  // Change here to toggle compiled variant

Variant compilation alters sensor initialization lists and updates how signals map to the FDCAN structures.

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Sensor Mapping Matrix

The board supports a wide range of analog and digital inputs, routed based on the compile-time configuration:

Sensor Name	Front Gateway Variant	Rear Gateway Variant	Driver Class / Header	Input Hardware Peripheral
Wheel Speed	Front Right & Front Left	Rear Right & Rear Left	MX5051	TIM4 period update / TIM2 input capture
Suspension Travel	Front Right & Front Left	Rear Right & Rear Left	KPM12J	ADC1 (DMA conversion)
APPS	APPS 1 & APPS 2	N/A	APPS	ADC2 (DMA conversion)
Steering Angle	Steering displacement	N/A	steering	ADC2 (DMA conversion)
Brake Pressure	N/A	Brake line sensor	PU8702	ADC2 (DMA conversion)
Current Sensor	N/A	JB Current (50A & 200A)	DHAB_S134	ADC2 (DMA conversion)
Coolant Temp	N/A	Temp 1 & Temp 2	GE1935	ADC2 (DMA) & ADC1 (DMA)
Coolant Flow	N/A	Flow rate sensor	debit_2061	EXTI Interrupt (GPIO pulse counter)
Digital Inputs	Ready-To-Drive (R2D) button	Shutdown Circuit (SDC)	debouncer	GPIO Digital Input

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NMOS Output Control & Hysteresis

The board manages high-side/low-side switching via on-board NMOS transistors (repos/CAN-Gateway/Core/Src/App/SensorsIO/nmos_vars.c):

• Front Gateway Variant: Controls the R2D button LED (NMOS1_Pin) blinking period configured via CAN command.
• Rear Gateway Variant:
  • Brake LED Output (NMOS1_Pin): Automatically driven based on PU8702 brake pressure with hysteresis to prevent output chatter:
    • Turn ON Threshold: Brake pressure $\ge 2.3\text{ bar}$
    • Turn OFF Threshold: Brake pressure $\le 1.7\text{ bar}$
    • Hysteresis Band ($1.7\text{ bar}<P<2.3\text{ bar}$): Retains the previous output state.
  • R2D Buzzer Output (NMOS2_Pin): Controlled directly by incoming CAN message state.

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Sensor Calibration & NVM Storage

Critical analog sensors require on-the-fly range calibration (such as APPS and steering sensors). The calibration sequences automatically register raw min/max voltages and save them to internal flash using the nimaltd/ee EEPROM Emulation Library.

For deep-dives into NVM configuration and calibration drivers, see:

• Sensor Recalibration & NVM Storage
• DHAB S134 driver reference
• DHAB S134 physical configuration