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Update drv_pwm.c #153

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Update drv_pwm.c #153

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544bb17
Update drv_pwm.c
Crashpilot1000 Jul 31, 2014
91761fc
Update drv_pwm.c
Crashpilot1000 Jul 31, 2014
5a9468c
Update drv_pwm.c
Crashpilot1000 Aug 1, 2014
7654af3
Update drv_pwm.c
Crashpilot1000 Aug 2, 2014
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45 changes: 33 additions & 12 deletions src/drv_pwm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -281,24 +281,45 @@ static void failsafeCheck(uint8_t channel, uint16_t pulse)
}
}

// Contains detection & fix for the "8 channels in 18ms Frsky problem" see:
// http://diydrones.com/profiles/blogs/why-frsky-cppm-signal-is-so-disappointing
// http://forums.openpilot.org/topic/16146-cc3d-with-frsky-8-channels-in-cppm-mode/
// Tested on: Frsky D8R-II and Frsky D4FR
static void ppmCallback(uint8_t port, uint16_t capture)
{
(void)port;
uint16_t diff;
static uint16_t now;
uint16_t newval = capture;
static uint16_t last = 0;
static uint8_t chan = 0;

last = now;
now = capture;
diff = now - last;

if (diff > 2700) { // Per http://www.rcgroups.com/forums/showpost.php?p=21996147&postcount=3960 "So, if you use 2.5ms or higher as being the reset for the PPM stream start, you will be fine. I use 2.7ms just to be safe."
static uint16_t frametime = 0;
static int8_t chan = 0;
static int8_t chan_order = 0;
static uint8_t frsky_problemcnt = 0;
uint16_t diff = newval - last;
bool sync = diff > 2700; // rcgroups.com/forums/showpost.php?p=21996147&postcount=3960 "So, if you use 2.5ms or higher as being the reset for the PPM stream start, you will be fine. I use 2.7ms just to be safe."
last = newval;

if (frsky_problemcnt == 30)
sync |= chan == 8; // FrSky 18ms Fix, force sync after 8 channels
else
frametime += diff;

if (sync) {
if (frsky_problemcnt != 30) {
if (frametime < 18300 && chan == 8)
frsky_problemcnt++;
else
frsky_problemcnt = 0;
frametime = 0;
}
chan = 0;
chan_order = 0;
} else {
if (diff > PULSE_MIN && diff < PULSE_MAX && chan < MAX_INPUTS) { // 750 to 2250 ms is our 'valid' channel range
captures[chan] = diff;
failsafeCheck(chan, diff);
if (diff > PULSE_MIN && diff < PULSE_MAX && chan == chan_order) { // Only capture if channel order is correct and Range: 750 to 2250 ms
if (chan < MAX_INPUTS) { // Needed and incoming channelnumbers can be different.
captures[chan] = diff;
failsafeCheck(chan, diff);
}
chan_order++;
}
chan++;
}
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