Communication Module

Overview

This module encompasses all communication subsystems in the Galvanic Isolator: CAN bus for vehicle-level integration and UART (RS-232) for inverter interface. The implementation emphasizes reliability through interrupt-driven hardware interfaces, ring buffers, and efficient deferred processing.

Code Organization

• Headers: Core/Inc/App/Communication/
• Source: Core/Src/App/Communication/
• UART Implementation: uart_comm.h, uart_comm.c
• CAN Implementation: can_comm.h, can_comm.c, can_driver.h, can_driver.c

Documentation Split

For detailed protocol information, see the specialized documents:

UART/RS-232 Communication

Covers the inverter serial interface with:

• DMA circular buffering - Continuous non-blocking reception into 2048-byte buffer
• Idle Line detection - Automatic message boundary detection (~95 µs idle threshold)
• Key=value protocol - RS-232 telemetry format (S, U, I, RPM, PWM, temperatures)
• Speed control encoding - Compact command format (e.g., s04++ for 44% speed)
• Pass-through mode - Bridge UART data across CAN for remote debugging

CAN Bus Communication

Covers the vehicle integration network with:

• FDCAN peripheral - STM32L562 hardware, 11-bit IDs, classic CAN 2.0B format
• Status frames - Periodic 50 Hz telemetry broadcast (PWM, voltage, current, RPM, temperatures)
• Debug frames - On-demand diagnostic information
• Bootloader frames - Remote firmware update and device programming
• Pass-through framing - Multi-frame UART data tunneling with START/END markers
• Ring buffer processing - 128-frame buffering with batch ISR limits
• Bus-off recovery - Automatic error state handling

System Architecture

Data Flow Sequence

Quick Reference Guide

UART Communication Cheat Sheet

Item	Value	Notes
Peripheral	UART4	STM32L562xx
Baud Rate	115200 8N1	RS-232 compatible
RX Buffer	2048 bytes	Circular, DMA-fed
Trigger	Idle Line	~95 µs @ 115200
Poll Rate	1-3 ms	Main task loop
Speed Encoding	Compact	s04++ = 44%, m = 100%
Telemetry Format	Key=Value	S=2.45, RPM=2450

Example UART Speed Commands:

0         → 0% (stop)
s1----    → 4% (4 dashes)
s04++     → 44% (tens=4, ++=additional 4%)
m         → 100% (max speed)

CAN Bus Cheat Sheet

Item	Value	Notes
Peripheral	FDCAN	STM32L562xx
Protocol	CAN 2.0B Classic	11-bit standard IDs
Bitrate	500 kbps (typical)	Configurable
RX Buffer	128 frames	Ring buffer
TX Buffer	128 frames	Queued frames
Status Rate	50 Hz	20 ms period
ISR Batch Size	2 frames	Prevents overrun
Process Budget	8 frames	Per task cycle
Passthrough Delay	1 ms	Inter-frame spacing

Message ID Ranges:

0x020-0x021 → Left inverter status (L_ID=0x004)
0x030-0x031 → Right inverter status (R_ID=0x005)
0x0E0       → ECU command broadcast
0x4F0-0x4F1 → Bootloader & programming
0x023-0x025 → Left inverter passthrough
0x033-0x035 → Right inverter passthrough

Integration Notes

• UART polling should be called from main task loop (e.g., every 1-3 ms)
• CAN RX processing uses time budgets to prevent starvation
• Status frame transmission runs on 20 ms timer (50 Hz)
• Pass-through mode bridges UART↔CAN for remote diagnostics
• Hardware errors trigger FSM fault states for safety handling
• Both subsystems are transport-independent for future protocol additions