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AP_RCProtocol: increased robustness of SBUS parsing

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take full advantage of the frame gap to reduce CPU and the chance of a
bad decode
This commit is contained in:
Andrew Tridgell 2018-11-26 22:18:46 +11:00
parent 69c4fb671e
commit d4c2945a48
1 changed files with 12 additions and 1 deletions
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13
libraries/AP_RCProtocol/AP_RCProtocol_SBUS.cpp
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@ -226,11 +226,22 @@ void AP_RCProtocol_SBUS::process_pulse(uint32_t width_s0, uint32_t width_s1)
// support byte input
void AP_RCProtocol_SBUS::_process_byte(uint32_t timestamp_us, uint8_t b)
{
if (timestamp_us - byte_input.last_byte_us > 2000U ||
const bool have_frame_gap = (timestamp_us - byte_input.last_byte_us > 2000U);
if (have_frame_gap &&
byte_input.ofs == sizeof(byte_input.buf)) {
byte_input.ofs = 0;
}
byte_input.last_byte_us = timestamp_us;
if (b != 0x0F && byte_input.ofs == 0) {
// definately not SBUS, missing header byte
return;
}
if (byte_input.ofs == 0 && !have_frame_gap) {
// must have a frame gap before the start of a new SBUS frame
return;
}
byte_input.buf[byte_input.ofs++] = b;
if (byte_input.ofs == sizeof(byte_input.buf)) {