117 lines
3.4 KiB
C
117 lines
3.4 KiB
C
/*
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* (c) 2021 by Tomasz bla Fortuna
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* License: GPLv2
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*
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* This file is shared with the Shine firmware. Keep it in sync (and in the
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* shine's clang formatting).
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*
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* Implementation of a robust serial protocol which can handle single dropped
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* characters during transit without locking.
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*
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* At 115200, transmitting the shortest message takes 0.043ms, at 9600 - 0.52ms.
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*
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*/
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#include "protocol.h"
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#include "board.h"
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#include "ch.h"
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#include "hal.h"
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/* UART communication protocol state */
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protocol_t proto;
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void proto_init(protocol_t *proto, void (*callback)(const message_t *)) {
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proto->previous_id = 0;
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proto->callback = callback;
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proto->state = STATE_SYNC_1;
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proto->errors = 0;
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}
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static uint8_t msg_id = 0;
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void proto_tx(uint8_t cmd, const unsigned char *buf, int payload_size, int retries) {
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chDbgCheck(payload_size <= MAX_PAYLOAD_SIZE);
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const uint8_t header[5] = {
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0x7A, 0x1D, cmd, ++msg_id, payload_size,
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};
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/* We don't implement ACKs, yet some messages should not be lost. */
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for (int i = 0; i < retries; i++) {
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sdWrite(&PROTOCOL_SD, header, sizeof(header));
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if (payload_size) sdWrite(&PROTOCOL_SD, buf, payload_size);
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}
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}
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static inline void messageReceived(protocol_t *proto) {
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if (proto->buffer.msg_id != proto->previous_id) {
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/* It's not a resend / duplicate */
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proto->callback(&proto->buffer);
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proto->previous_id = proto->buffer.msg_id;
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}
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proto->state = STATE_SYNC_1;
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}
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void proto_consume(protocol_t *proto, uint8_t byte) {
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switch (proto->state) {
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case STATE_SYNC_1:
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if (byte == 0x7A) {
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proto->state = STATE_SYNC_2;
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} else {
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proto->errors++;
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}
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return;
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case STATE_SYNC_2:
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if (byte == 0x1D) {
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proto->state = STATE_CMD;
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} else {
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proto->state = STATE_SYNC_1;
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proto->errors++;
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}
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return;
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case STATE_CMD:
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proto->buffer.command = byte;
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proto->state = STATE_ID;
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return;
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case STATE_ID:
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proto->buffer.msg_id = byte;
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proto->state = STATE_PAYLOAD_SIZE;
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return;
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case STATE_PAYLOAD_SIZE:
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proto->buffer.payload_size = byte;
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if (proto->buffer.payload_size > MAX_PAYLOAD_SIZE) {
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proto->buffer.payload_size = MAX_PAYLOAD_SIZE;
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proto->errors++;
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}
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proto->payload_position = 0;
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if (proto->buffer.payload_size == 0) {
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/* No payload - whole message received */
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messageReceived(proto);
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} else {
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proto->state = STATE_PAYLOAD;
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}
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return;
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case STATE_PAYLOAD:
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/* NOTE: This could be read with sdReadTimeout probably, but that breaks
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* abstraction */
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proto->buffer.payload[proto->payload_position] = byte;
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proto->payload_position++;
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if (proto->payload_position == proto->buffer.payload_size) {
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/* Payload read - message received */
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messageReceived(proto);
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}
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return;
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}
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}
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void proto_silence(protocol_t *proto) {
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if (proto->state != STATE_SYNC_1) {
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proto->state = STATE_SYNC_1;
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proto->errors++;
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}
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}
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