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SBUS 32 Channel #536

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9027559
SBUS 32 Channel
jlpoltrack Oct 5, 2026
a37f76a
Feedback, work with AP & INAV
jlpoltrack Oct 5, 2026
67a8c9d
Don't send flags
jlpoltrack Oct 6, 2026
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1 change: 1 addition & 0 deletions mLRS/Common/protocols/sbus_protocol.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@

typedef enum {
SBUS_STX = 0x0F,
SBUS_STX_CH17_CH32 = 0x2F, // frame with channels 17-32, sent in between normal frames
SBUS_END_STX = 0x00,
} SBUS_STX_ENUM;

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97 changes: 66 additions & 31 deletions mLRS/CommonRx/out.cpp
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Expand Up @@ -35,6 +35,8 @@ void tOutBase::Init(tRxSetup* const _setup)

rc = {};
rc_channels32_tlast_ms = 0;
sbus_ch17_ch32_pending = false;
sbus_ch17_ch32_tstart_us = 0;

setup = _setup;
}
Expand Down Expand Up @@ -82,7 +84,7 @@ void tOutBase::Do(void)
switch (config) {
case OUT_CONFIG_SBUS:
case OUT_CONFIG_SBUS_INVERTED:
// nothing to do
do_sbus();
break;
case OUT_CONFIG_CRSF:
do_crsf();
Expand Down Expand Up @@ -163,21 +165,32 @@ void tOutBase::SendRcData(tRcData* const rc_orig, bool frame_missed, bool failsa
switch (config) {
case OUT_CONFIG_SBUS:
case OUT_CONFIG_SBUS_INVERTED:
send_sbus_rcdata(frame_missed, failsafe);
send_sbus_rcdata(frame_missed, failsafe, false);
if (do_rc_channels32()) { // ch17-32 frame is sent delayed, in do_sbus()
sbus_ch17_ch32_pending = true;
sbus_ch17_ch32_tstart_us = micros16();
}
break;
case OUT_CONFIG_CRSF:
send_crsf_rcdata();
if (rc.do_32channels) {
uint32_t tnow_ms = millis32();
if ((tnow_ms - rc_channels32_tlast_ms) < 200) break; // send only at 5 Hz
rc_channels32_tlast_ms = tnow_ms;
send_crsf_rcdata_0x17();
}
if (do_rc_channels32()) send_crsf_rcdata_0x17();
break;
}
}


// returns true if it is time to send channels 17-32
bool tOutBase::do_rc_channels32(void)
{
if (!rc.do_32channels) return false;

uint32_t tnow_ms = millis32();
if ((tnow_ms - rc_channels32_tlast_ms) < 200) return false; // send only at 5 Hz
rc_channels32_tlast_ms = tnow_ms;
return true;
}


void tOutBase::SendLinkStatistics(tOutLinkStats* const lstats)
{
switch (config) {
Expand Down Expand Up @@ -225,35 +238,43 @@ void tOutBase::SendLinkStatisticsDisconnected(void)
// SBus
//-------------------------------------------------------

void tOutBase::send_sbus_rcdata(bool frame_lost, bool failsafe)
// do_ch17_ch32 = true: frame with start byte 0x2F holding channels 17-32, as understood by INAV
void tOutBase::send_sbus_rcdata(bool frame_lost, bool failsafe, bool do_ch17_ch32)
{
tSBusFrame frame;
uint8_t ofs = (do_ch17_ch32) ? 16 : 0;

// chX = (((int32_t)(rc->ch[X]) - 1024) * 1920) / 2047 + 1000;
frame.ch.ch0 = rc_to_sbus(rc.ch[0]);
frame.ch.ch1 = rc_to_sbus(rc.ch[1]);
frame.ch.ch2 = rc_to_sbus(rc.ch[2]);
frame.ch.ch3 = rc_to_sbus(rc.ch[3]);
frame.ch.ch4 = rc_to_sbus(rc.ch[4]);
frame.ch.ch5 = rc_to_sbus(rc.ch[5]);
frame.ch.ch6 = rc_to_sbus(rc.ch[6]);
frame.ch.ch7 = rc_to_sbus(rc.ch[7]);
frame.ch.ch8 = rc_to_sbus(rc.ch[8]);
frame.ch.ch9 = rc_to_sbus(rc.ch[9]);
frame.ch.ch10 = rc_to_sbus(rc.ch[10]);
frame.ch.ch11 = rc_to_sbus(rc.ch[11]);
frame.ch.ch12 = rc_to_sbus(rc.ch[12]);
frame.ch.ch13 = rc_to_sbus(rc.ch[13]);
frame.ch.ch14 = rc_to_sbus(rc.ch[14]);
frame.ch.ch15 = rc_to_sbus(rc.ch[15]);

frame.ch.ch0 = rc_to_sbus(rc.ch[ofs + 0]);
frame.ch.ch1 = rc_to_sbus(rc.ch[ofs + 1]);
frame.ch.ch2 = rc_to_sbus(rc.ch[ofs + 2]);
frame.ch.ch3 = rc_to_sbus(rc.ch[ofs + 3]);
frame.ch.ch4 = rc_to_sbus(rc.ch[ofs + 4]);
frame.ch.ch5 = rc_to_sbus(rc.ch[ofs + 5]);
frame.ch.ch6 = rc_to_sbus(rc.ch[ofs + 6]);
frame.ch.ch7 = rc_to_sbus(rc.ch[ofs + 7]);
frame.ch.ch8 = rc_to_sbus(rc.ch[ofs + 8]);
frame.ch.ch9 = rc_to_sbus(rc.ch[ofs + 9]);
frame.ch.ch10 = rc_to_sbus(rc.ch[ofs + 10]);
frame.ch.ch11 = rc_to_sbus(rc.ch[ofs + 11]);
frame.ch.ch12 = rc_to_sbus(rc.ch[ofs + 12]);
frame.ch.ch13 = rc_to_sbus(rc.ch[ofs + 13]);
frame.ch.ch14 = rc_to_sbus(rc.ch[ofs + 14]);
frame.ch.ch15 = rc_to_sbus(rc.ch[ofs + 15]);

// no flags in the ch17-32 frame, INAV ors them into each following frame until the next one
uint8_t flags = 0;
if (rc.ch[16] >= 1450) flags |= SBUS_FLAG_CH17; // 1450 = +50%
if (rc.ch[17] >= 1450) flags |= SBUS_FLAG_CH18;
if (frame_lost) flags |= SBUS_FLAG_FRAME_LOST;
if (failsafe) flags |= SBUS_FLAG_FAILSAFE;
if (!do_ch17_ch32) {
// in 32 channels mode ch17,18 are in the ch17-32 frame, INAV would mirror the flags to ch33,34
if (!rc.do_32channels) {
if (rc.ch[16] >= 1450) flags |= SBUS_FLAG_CH17; // 1450 = +50%
if (rc.ch[17] >= 1450) flags |= SBUS_FLAG_CH18;
}
if (frame_lost) flags |= SBUS_FLAG_FRAME_LOST;
if (failsafe) flags |= SBUS_FLAG_FAILSAFE;
}

frame.stx = SBUS_STX;
frame.stx = (do_ch17_ch32) ? SBUS_STX_CH17_CH32 : SBUS_STX;

frame.flags = flags;
frame.end_stx = SBUS_END_STX;
Expand All @@ -262,6 +283,20 @@ tSBusFrame frame;
}


// sends the ch17-32 frame in the idle time after the normal frame, which takes 3 ms
// INAV needs 3 ms gap after the normal frame, ArduPilot needs 2 ms gap before the next normal frame
void tOutBase::do_sbus(void)
{
if (!sbus_ch17_ch32_pending) return;

uint16_t dt = micros16() - sbus_ch17_ch32_tstart_us;
if (dt > 6500) {
sbus_ch17_ch32_pending = false;
send_sbus_rcdata(false, false, true);
}
}


//-------------------------------------------------------
// Crsf
//-------------------------------------------------------
Expand Down
6 changes: 5 additions & 1 deletion mLRS/CommonRx/out.h
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Original file line number Diff line number Diff line change
Expand Up @@ -61,10 +61,12 @@ class tOutBase
tRcData* GetRcDataPtr(void) { return &rc; }

private:
void send_sbus_rcdata(bool frame_lost, bool failsafe);
bool do_rc_channels32(void);
void send_sbus_rcdata(bool frame_lost, bool failsafe, bool do_ch17_ch32);
void send_crsf_rcdata(void);
void send_crsf_rcdata_0x17(void);
void send_crsf_linkstatistics(tOutLinkStats* const lstats);
void do_sbus(void);
void do_crsf(void);

virtual void putbuf(uint8_t* const buf, uint16_t len) {}
Expand All @@ -84,6 +86,8 @@ class tOutBase

tRcData rc;
uint32_t rc_channels32_tlast_ms;
bool sbus_ch17_ch32_pending;
uint16_t sbus_ch17_ch32_tstart_us;
};


Expand Down