90 lines
2.8 KiB
C
90 lines
2.8 KiB
C
/**
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* @file protocol.c
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* @brief AliceRC communication protocol implementation
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*/
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#include <string.h>
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#include "protocol.h"
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void protocol_init(void)
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{
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/* Nothing to initialize for now */
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}
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void protocol_pack_sbus(const uint16_t *channels, uint8_t *sbus_data)
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{
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memset(sbus_data, 0, 22);
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/* Pack 16 × 11-bit channels into 22 bytes, little-endian bitstream */
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for (int i = 0; i < SBUS_CHANNEL_COUNT; i++) {
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uint16_t ch = channels[i] & 0x07FF; /* Mask to 11 bits */
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int byte_idx = (i * SBUS_CHANNEL_BITS) / 8;
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int bit_off = (i * SBUS_CHANNEL_BITS) % 8;
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sbus_data[byte_idx] |= (ch << bit_off) & 0xFF;
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sbus_data[byte_idx + 1] |= (ch >> (8 - bit_off)) & 0xFF;
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if (bit_off > 5) {
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/* 11-bit crosses 3-byte boundary when bit_off >= 6 */
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sbus_data[byte_idx + 2] |= (ch >> (16 - bit_off)) & 0xFF;
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}
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}
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}
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void protocol_unpack_sbus(const uint8_t *sbus_data, uint16_t *channels)
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{
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for (int i = 0; i < SBUS_CHANNEL_COUNT; i++) {
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int byte_idx = (i * SBUS_CHANNEL_BITS) / 8;
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int bit_off = (i * SBUS_CHANNEL_BITS) % 8;
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uint16_t ch = sbus_data[byte_idx] >> bit_off;
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ch |= (uint16_t)(sbus_data[byte_idx + 1]) << (8 - bit_off);
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if (bit_off > 5) {
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ch |= (uint16_t)(sbus_data[byte_idx + 2]) << (16 - bit_off);
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}
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channels[i] = ch & 0x07FF;
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}
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}
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void protocol_build_tx_payload(rf_tx_payload_t *payload,
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const uint16_t *adc_channels,
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uint8_t model_id,
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uint8_t seq)
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{
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uint16_t sbus_channels[SBUS_CHANNEL_COUNT];
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/* Convert 8 ADC channels to SBUS range, center the rest */
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for (int i = 0; i < 8; i++) {
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sbus_channels[i] = protocol_map_to_sbus(adc_channels[i]);
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}
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for (int i = 8; i < SBUS_CHANNEL_COUNT; i++) {
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sbus_channels[i] = SBUS_CENTER;
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}
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/* Build payload */
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memset(payload, 0, sizeof(rf_tx_payload_t));
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payload->frame_id = FRAME_ID_CHANNELS;
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payload->seq = seq;
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payload->model_id = model_id;
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payload->flags = 0;
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protocol_pack_sbus(sbus_channels, payload->sbus_data);
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}
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void protocol_parse_telemetry(const rf_rx_telemetry_t *telemetry,
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uint16_t *battery_mv)
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{
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if (telemetry->frame_id == FRAME_ID_TELEMETRY) {
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/* Battery voltage is big-endian */
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*battery_mv = (telemetry->battery_mv >> 8) |
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(telemetry->battery_mv << 8);
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}
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}
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uint16_t protocol_map_to_sbus(uint16_t adc_value)
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{
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/* Map 12-bit ADC (0-4095) to SBUS range (200-1844) */
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uint32_t result = SBUS_MIN + ((uint32_t)adc_value * (SBUS_MAX - SBUS_MIN) / 4095);
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if (result > SBUS_MAX) result = SBUS_MAX;
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return (uint16_t)result;
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}
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