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ardupilot/libraries/AP_RCProtocol/AP_RCProtocol_ST24.cpp

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/*
SUMD decoder, based on PX4Firmware/src/rc/lib/rc/sumd.c from PX4Firmware
modified for use in AP_HAL_* by Andrew Tridgell
*/
/****************************************************************************
*
* Copyright (c) 2015 PX4 Development Team. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/*
* @file sumd.h
*
* RC protocol definition for Graupner HoTT transmitter (SUMD/SUMH Protocol)
*
* @author Marco Bauer <marco@wtns.de>
*/
#include "AP_RCProtocol_ST24.h"
// #define SUMD_DEBUG
extern const AP_HAL::HAL& hal;
uint8_t AP_RCProtocol_ST24::st24_crc8(uint8_t *ptr, uint8_t len)
{
uint8_t i, crc ;
crc = 0;
while (len--) {
for (i = 0x80; i != 0; i >>= 1) {
if ((crc & 0x80) != 0) {
crc <<= 1;
crc ^= 0x07;
} else {
crc <<= 1;
}
if ((*ptr & i) != 0) {
crc ^= 0x07;
}
}
ptr++;
}
return (crc);
}
void AP_RCProtocol_ST24::process_pulse(uint32_t width_s0, uint32_t width_s1)
{
// convert to bit widths, allowing for up to about 4usec error, assuming 115200 bps
uint16_t bits_s0 = ((width_s0+4)*(uint32_t)115200) / 1000000;
uint16_t bits_s1 = ((width_s1+4)*(uint32_t)115200) / 1000000;
uint8_t bit_ofs, byte_ofs;
uint16_t nbits;
if (bits_s0 == 0 || bits_s1 == 0) {
// invalid data
goto reset;
}
byte_ofs = st24_state.bit_ofs/10;
bit_ofs = st24_state.bit_ofs%10;
if (byte_ofs >= ST24_MAX_FRAMELEN) {
goto reset;
}
// pull in the high bits
nbits = bits_s0;
if (nbits+bit_ofs > 10) {
nbits = 10 - bit_ofs;
}
st24_state.bytes[byte_ofs] |= ((1U<<nbits)-1) << bit_ofs;
st24_state.bit_ofs += nbits;
bit_ofs += nbits;
if (bits_s0 - nbits > 10) {
// we have a full frame
uint8_t byte;
uint8_t i;
for (i=0; i <= byte_ofs; i++) {
// get raw data
uint16_t v = st24_state.bytes[i];
// check start bit
if ((v & 1) != 0) {
break;
}
// check stop bits
if ((v & 0x200) != 0x200) {
break;
}
byte = ((v>>1) & 0xFF);
process_byte(byte);
}
memset(&st24_state, 0, sizeof(st24_state));
}
byte_ofs = st24_state.bit_ofs/10;
bit_ofs = st24_state.bit_ofs%10;
if (bits_s1+bit_ofs > 10) {
// invalid data
goto reset;
}
// pull in the low bits
st24_state.bit_ofs += bits_s1;
return;
reset:
memset(&st24_state, 0, sizeof(st24_state));
}
void AP_RCProtocol_ST24::process_byte(uint8_t byte)
{
switch (_decode_state) {
case ST24_DECODE_STATE_UNSYNCED:
if (byte == ST24_STX1) {
_decode_state = ST24_DECODE_STATE_GOT_STX1;
}
break;
case ST24_DECODE_STATE_GOT_STX1:
if (byte == ST24_STX2) {
_decode_state = ST24_DECODE_STATE_GOT_STX2;
} else {
_decode_state = ST24_DECODE_STATE_UNSYNCED;
}
break;
case ST24_DECODE_STATE_GOT_STX2:
/* ensure no data overflow failure or hack is possible */
if ((unsigned)byte <= sizeof(_rxpacket.length) + sizeof(_rxpacket.type) + sizeof(_rxpacket.st24_data)) {
_rxpacket.length = byte;
_rxlen = 0;
_decode_state = ST24_DECODE_STATE_GOT_LEN;
} else {
_decode_state = ST24_DECODE_STATE_UNSYNCED;
}
break;
case ST24_DECODE_STATE_GOT_LEN:
_rxpacket.type = byte;
_rxlen++;
_decode_state = ST24_DECODE_STATE_GOT_TYPE;
break;
case ST24_DECODE_STATE_GOT_TYPE:
_rxpacket.st24_data[_rxlen - 1] = byte;
_rxlen++;
if (_rxlen == (_rxpacket.length - 1)) {
_decode_state = ST24_DECODE_STATE_GOT_DATA;
}
break;
case ST24_DECODE_STATE_GOT_DATA:
_rxpacket.crc8 = byte;
_rxlen++;
if (st24_crc8((uint8_t *) & (_rxpacket.length), _rxlen) == _rxpacket.crc8) {
/* decode the actual packet */
switch (_rxpacket.type) {
case ST24_PACKET_TYPE_CHANNELDATA12: {
uint16_t values[12];
uint8_t num_values;
ChannelData12 *d = (ChannelData12 *)_rxpacket.st24_data;
//TBD: add support for RSSI
// *rssi = d->rssi;
//*rx_count = d->packet_count;
/* this can lead to rounding of the strides */
num_values = (MAX_RCIN_CHANNELS < 12) ? MAX_RCIN_CHANNELS : 12;
unsigned stride_count = (num_values * 3) / 2;
unsigned chan_index = 0;
for (unsigned i = 0; i < stride_count; i += 3) {
values[chan_index] = ((uint16_t)d->channel[i] << 4);
values[chan_index] |= ((uint16_t)(0xF0 & d->channel[i + 1]) >> 4);
/* convert values to 1000-2000 ppm encoding in a not too sloppy fashion */
values[chan_index] = (uint16_t)(values[chan_index] * ST24_SCALE_FACTOR + .5f) + ST24_SCALE_OFFSET;
chan_index++;
values[chan_index] = ((uint16_t)d->channel[i + 2]);
values[chan_index] |= (((uint16_t)(0x0F & d->channel[i + 1])) << 8);
/* convert values to 1000-2000 ppm encoding in a not too sloppy fashion */
values[chan_index] = (uint16_t)(values[chan_index] * ST24_SCALE_FACTOR + .5f) + ST24_SCALE_OFFSET;
chan_index++;
}
}
break;
case ST24_PACKET_TYPE_CHANNELDATA24: {
uint16_t values[24];
uint8_t num_values;
ChannelData24 *d = (ChannelData24 *)&_rxpacket.st24_data;
//*rssi = d->rssi;
//*rx_count = d->packet_count;
/* this can lead to rounding of the strides */
num_values = (MAX_RCIN_CHANNELS < 24) ? MAX_RCIN_CHANNELS : 24;
unsigned stride_count = (num_values * 3) / 2;
unsigned chan_index = 0;
for (unsigned i = 0; i < stride_count; i += 3) {
values[chan_index] = ((uint16_t)d->channel[i] << 4);
values[chan_index] |= ((uint16_t)(0xF0 & d->channel[i + 1]) >> 4);
/* convert values to 1000-2000 ppm encoding in a not too sloppy fashion */
values[chan_index] = (uint16_t)(values[chan_index] * ST24_SCALE_FACTOR + .5f) + ST24_SCALE_OFFSET;
chan_index++;
values[chan_index] = ((uint16_t)d->channel[i + 2]);
values[chan_index] |= (((uint16_t)(0x0F & d->channel[i + 1])) << 8);
/* convert values to 1000-2000 ppm encoding in a not too sloppy fashion */
values[chan_index] = (uint16_t)(values[chan_index] * ST24_SCALE_FACTOR + .5f) + ST24_SCALE_OFFSET;
chan_index++;
}
}
break;
case ST24_PACKET_TYPE_TRANSMITTERGPSDATA: {
// ReceiverFcPacket* d = (ReceiverFcPacket*)&_rxpacket.st24_data;
/* we silently ignore this data for now, as it is unused */
}
break;
default:
break;
}
} else {
/* decoding failed */
}
_decode_state = ST24_DECODE_STATE_UNSYNCED;
break;
}
}
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