watchrobot/libraries/AP_HAL/utility/sumd.h

/*
  SUMD decoder, based on PX4Firmware/src/rc/lib/rc/sumd.c from PX4Firmware
  modified for use in AP_HAL_* by Andrew Tridgell
 */
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/**
 * @file sumd.h
 *
 * RC protocol definition for Graupner HoTT transmitter
 *
 * @author Marco Bauer <marco@wtns.de>
 */

#pragma once

/**
 * Decoder for SUMD/SUMH protocol
 *
 * @param byte current char to read
 * @param rssi pointer to a byte where the RSSI value is written back to
 * @param rx_count pointer to a byte where the receive count of packets signce last wireless frame is written back to
 * @param channels pointer to a datastructure of size max_chan_count where channel values (12 bit) are written back to
 * @param max_chan_count maximum channels to decode - if more channels are decoded, the last n are skipped and success (0) is returned
 * @return 0 for success (a decoded packet), 1 for no packet yet (accumulating), 2 for unknown packet, 3 for out of sync, 4 for checksum error
 */
int sumd_decode(uint8_t byte, uint8_t *rssi, uint8_t *rx_count, uint16_t *channel_count,
                uint16_t *channels, uint16_t max_chan_count);