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pio_ppm - RC PPM protocol example works on GPIO 3 #414

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5bc1c3c
pio_ppm - RC PPM protocol example works on GPIO 3
elmot Aug 20, 2023
da095f2
pio_ppm - More precise timing
elmot Aug 20, 2023
7a0b42e
pio_ppm - Code polishing
elmot Aug 22, 2023
a6e1eac
pio_ppm - Comments polishing
elmot Aug 22, 2023
38d1130
pio_ppm - Fixes after testing on real hardware
elmot Aug 22, 2023
439f5f4
pio_ppm - Comments polishing
elmot Aug 23, 2023
1a70e4a
pio_ppm - Proper synchro gap length
elmot Aug 28, 2023
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8 changes: 4 additions & 4 deletions pio/ppm/ppm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,10 +8,10 @@
* 8-channel Radio Control PPM example
* Output on GPIO3
*
* >=5ms 0.5ms 1-2ms 0.5ms 1-2ms 0.5ms 1-2ms 0.5ms
* synchro strobe ch0 value strobe ch1 value strobe ch8 value strobe
* _______ _______ _______ _______
* _______...__| |_____________| |___________...| |____________| |_

* synchro / ch0 value 1-2ms \/ ch0 value 1-2ms \ / ch8 value 1-2ms \
* >=5ms _______ -500ms _______ _______ _______
* _______...__| 0.5ms |_____________| 0.5ms |___________|...| 0.5ms |____________| 0.5ms |_
*/
#include <stdio.h>

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4 changes: 2 additions & 2 deletions pio/ppm/ppm.pio
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Expand Up @@ -39,8 +39,8 @@ void ppm_handler() {
}
}

// 500 microseconds strobe and gap microseconds
#define BUILD_CH_VALUE(gap_us) (((500 - 1) << 16) + (gap_us - 1))
// 500 microseconds strobe + gap = value (microseconds)
#define BUILD_CH_VALUE(value_us) (((500 - 1) << 16) + (value_us - 500 - 1))

static inline void ppm_program_init(PIO pio, uint pin) {
ppm_data.pio = pio == NULL ? pio0 : pio;
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