SENTRx - SENT Protocol Receiver

Overview

SENTRx is a library for receiving and decoding data using the SENT (Single Edge Nibble Transmission) protocol. It is implemented in C and designed to work with STM32 microcontrollers using the HAL library for timer input capture.

Features

• Supports decoding SENT fast and slow channel messages.
• Implements input capture via STM32 HAL timers.
• Provides callback mechanisms for received messages.
• Supports both standard and enhanced slow channel messages.
• Includes automatic synchronization and error checking via CRC validation.

File Structure

• sent_rx.h - Header file containing the SENTRx API, data structures, and macros.
• sent_rx.c - Implementation of the SENTRx receiver functions.

SENTRx Data Structures

SENTRxHandle_t

A handle structure containing:

• Base SENT handle (SENTHandle_t)
• User data pointer
• Capture timing data
• Receiver state machine
• Message buffers for fast and slow channels
• Callback functions for received messages
• Buffers for slow channel bit collection

Callbacks

• SENTRxCallback_t - Called when a fast channel message is received.
• SENTRxSlowCallback_t - Called when a slow channel message is received.

API Functions

uint8_t SENTRx_init(SENTRxHandle_t *const handle, SENTHandleInit_t *const init, SENTRxCallback_t rx_callback, SENTRxSlowCallback_t slow_rx_callback, void *user_data);

Initializes the SENT receiver with the given timer and callbacks.

uint8_t SENTRx_start(SENTRxHandle_t *const handle);

Starts the SENT receiver by enabling timer input capture.

void SENTRx_InputCaptureCallback(SENTRxHandle_t *const handle);

Handles incoming pulse capture events, processes nibbles, and triggers the state machine.

SENT Protocol Handling

Synchronization

• The receiver synchronizes based on a predefined pulse width corresponding to the SENT sync frame.

Fast Channel Processing

• Nibbles are collected and converted into a full message.
• CRC validation is performed before invoking the callback.

Slow Channel Processing

• Uses a state machine to collect slow channel data bits.
• Supports both short and enhanced slow messages.

Usage Example

void SENT_MessageCallback(SENTMsg_t *const msg, void *user_data) {
    // Process fast channel message
}

void SENT_SlowMessageCallback(SENTSlowMsg_t *const msg, void *user_data) {
    // Process slow channel message
}

SENTRxHandle_t sent_rx;
SENTHandleInit_t init = { .htim = &htim1, .channel = TIM_CHANNEL_1 };

if (SENTRx_init(&sent_rx, &init, SENT_MessageCallback, SENT_SlowMessageCallback, NULL)) {
    SENTRx_start(&sent_rx);
}

Dependencies

• STM32 HAL library (for timer handling)
• sent.h (base SENT protocol definitions and utilities)

License

This project is released under the MIT License.