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GTRUVIN9XPCB: DSM2=PPM mode -- Implemented hardware switching of PPM_OUT pin

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and compensated for main clock synchronisation to get accurate 8us bit 
lengths, as measured on the logic analsyser. 

Specifically, all 1 and 0 bits now measure 8.000us in length, instead of 
varyting from 6.250us to 10.750us, as before.

NOTE: A similar len-5 / len+3 compensation is almost certainly required
      to improve bit timing on the stock board, in software bit-bang mode,
      but I did not want to commit such a change to trunk without being
      able to bench test it first. The values might differ slightly, due
      to the number of instruction cycles executed before the actual
      PORT B bit toggle code is reached. But it will NOT be the same for 
      both 1 and 0 bits.
This commit is contained in:
gruvin@gmail.com
2012-11-01 08:44:14 +00:00
parent d02ef1b603
commit 37387f91fd
2 changed files with 62 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/Makefile
+1
View File
@@ -183,6 +183,7 @@ EXTRA_ROTARY_ENCODERS = NO
# On G9X V4 board, when VOICE=NO:
# PORTH:7 --> Transistion LOW to HIGH = start of setupPulses(). Transistion HIGH to LOW = end of setupPulses().
# PORTH:6 --> LOW->HIGH = start of mixer calcs. HIGH->LOW, end of mixer calcs.
# Values = YES, NO
DEBUG = NO
# Flight Phases
src/pulses_avr.cpp
+61 -9
View File
@@ -501,13 +501,27 @@ void sendByteDsm2(uint8_t b) //max 10changes 0 10 10 10 10 1
if(lev == nlev){
len += BITLEN_DSM2;
}else{
#if defined (GRUVIN9XPCB)
// G: Compensate for main clock synchronisation -- to get accurate 8us bit length
// NOTE: This is probably required for the stock board (S/W bit-bang mode) also,
// but I did not want to commit that to trunk without testing it first.
if (nlev)
_send_1(len-5);// -1);
else
_send_1(len+3);
#else
_send_1(len -1);
#endif
len = BITLEN_DSM2;
lev = nlev;
}
b = (b>>1) | 0x80; //shift in stop bit
}
#if defined (GRUVIN9XPCB)
_send_1(len+BITLEN_DSM2+3); // 2 stop bits
#else
_send_1(len+BITLEN_DSM2-1); // 2 stop bits
#endif
}
void setupPulsesDsm2()
@@ -556,7 +570,10 @@ void setupPulsesDsm2()
sendByteDsm2(dsmDat[counter]);
pulses2MHzWPtr -= 1; //remove last stopbits and
_send_1(255); //prolong them
//G: Removed to get waveform correct on analyser
//_send_1(255); //prolong them
_send_1(0); //end of pulse stream
pulses2MHzRPtr = pulses2MHz;
@@ -730,7 +747,7 @@ void setupPulses()
{
uint8_t required_protocol = g_model.protocol;
#if defined(PCBGRUVIN9X) && defined(DEBUG) && !defined(VOICE)
#if defined(DEBUG) && !defined(VOICE)
PORTH |= 0x80; // PORTH:7 LOW->HIGH signals start of setupPulses()
#endif
@@ -751,10 +768,12 @@ void setupPulses()
TCNT1 = 300; // Past the OCR1C value
ICR1 = 44000; // Next frame starts in 22 mS
#if defined(PCBGRUVIN9X)
TIMSK1 &= ~0x2F; // All interrupts off
TIMSK1 &= ~0x2F; // All Timer1 interrupts off
TIFR1 = 0x2F;
TIMSK1 |= 0x28; // Enable CAPT and COMPC
TCCR1A = (0 << WGM10); // Also disconnects OC1B for PPM_OUT bit-bang mode
TIMSK1 |= 0x28; // Enable COMPC and CAPT interrupts
TCCR1A = (0 << WGM10); // Set output waveform mode to normal, for now. Note that
// WGM will be set to toggle OCR1B pin on compare capture,
// in next switch(required_protocol) {...}, below
#else
TIMSK &= ~0x3C; // All Timer1 interrupts off
TIFR = 0x3C;
@@ -873,6 +892,12 @@ void setupPulses()
case PROTO_DSM2:
sei();
setupPulsesDsm2();
#if defined(PCBGRUVIN9X)
// Ensure each DSM packet starts out with the correct bit polarity
TCCR1A = (0 << WGM10) | (3<<COM1B1); // Have Waveform Generator Mode 'SET' OCR1B pin on next compare event and ...
TCCR1C = (1<<FOC1B); // ... force compare event, to set OCR1B pin high now.
TCCR1A = (1<<COM1B0); // Output is ready. Initiate OCR1B pin *TOGGLE* mode (H/W switching.)
#endif
break;
#endif
@@ -890,9 +915,10 @@ void setupPulses()
break;
}
#if defined(PCBGRUVIN9X) && defined(DEBUG) && !defined(VOICE)
#if defined(DEBUG) && !defined(VOICE)
PORTH &= ~0x80; // PORTH:7 HIGH->LOW signals end of setupPulses()
#endif
}
#ifndef SIMU
@@ -900,12 +926,35 @@ void setupPulses()
#if defined(DSM2_PPM) || defined(PXX)
ISR(TIMER1_CAPT_vect) // 2MHz pulse generation
{
#if defined (PCBGRUVIN9X)
/*** G9X V4 hardware toggled PPM_out avoids interrupt latency jitter on the output.
In most (but not all) foreseeable cases, the jitter removal afforded by this is
inside the bit timing tolerances of async serial data at 125,000bps. But I cannot
afford to crash models. So I like to have the extra assurance. Gruvin.
(It can be done on the stock board's PB7 too. Nove LED BL to PB0.) ***/
// OCR1B output pin (PPM_OUT) is pre-set to HIGH in setupPulses -- for safety, on each
// and every frame -- and configured to toggle on each OCR1B / TC1 count register match.
// All we need to do here then, is update the compare regisiter(s) ...
uint8_t x ;
PORTB ^= (1<<OUT_B_PPM);
x = *pulses2MHzRPtr++; // Byte size
ICR1 = x;
OCR1B = (uint16_t)x; // Duplicate capture compare value for OCR1B, because Timer1 is in CTC mode
// and thus we cannot use the OCR1B INT vector. (Should have put PPM_OUT
// pin on OCR1A. Oh well.)
#else
uint8_t x ;
PORTB ^= (1<<OUT_B_PPM); // Toggle PPM_OUT
x = *pulses2MHzRPtr++; // Byte size
ICR1 = x ;
if (x > 200) PORTB |= (1<<OUT_B_PPM); // Make sure pulses are the correct way up
heartbeat |= HEART_TIMER_PULSES; // TODO why not in TIMER1_COMPB_vect (in setupPulses)?
if (x > 200) PORTB |= (1<<OUT_B_PPM); // Make sure pulses are the correct way up.
#endif
}
#if defined(PXX)
@@ -954,6 +1003,9 @@ ISR(TIMER1_COMPC_vect) // DSM2 or PXX end of frame
// sei will be called inside setupPulses()
setupPulses();
}
heartbeat |= HEART_TIMER_PULSES;
#endif
#if defined(DSM2_PPM) && defined(PXX)