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dshot: check for bad pulses and handle wrap correctly #78

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dshot: check for bad pulses and handle wrap correctly #78

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48 changes: 25 additions & 23 deletions Src/dshot.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,45 +12,47 @@
#include "sounds.h"
#include "targets.h"

int dpulse[16] = { 0 };
static uint8_t dpulse[16];

const char gcr_encode_table[16] = {
static const uint8_t gcr_encode_table[16] = {
0b11001, 0b11011, 0b10010, 0b10011, 0b11101, 0b10101, 0b10110, 0b10111,
0b11010, 0b01001, 0b01010, 0b01011, 0b11110, 0b01101, 0b01110, 0b01111
};

char EDT_ARM_ENABLE = 0;
char EDT_ARMED = 0;
int shift_amount = 0;
uint32_t gcrnumber;
char EDT_ARM_ENABLE;
char EDT_ARMED;
static int shift_amount;
static uint32_t gcrnumber;
extern int zero_crosses;
extern char send_telemetry;
extern uint8_t max_duty_cycle_change;
int dshot_full_number;
static uint32_t dshot_full_number;
extern char play_tone_flag;
uint8_t command_count = 0;
uint8_t last_command = 0;
uint8_t high_pin_count = 0;
uint32_t gcr[37] = { 0 };
uint16_t dshot_frametime;
uint16_t dshot_goodcounts;
uint16_t dshot_badcounts;
char dshot_extended_telemetry = 0;
uint16_t send_extended_dshot = 0;
uint16_t processtime = 0;
uint16_t halfpulsetime = 0;
static uint8_t command_count;
static uint8_t last_command;
static uint8_t high_pin_count;
uint32_t gcr[37];
static uint16_t dshot_frametime;
static uint16_t dshot_goodcounts;
static uint16_t dshot_badcounts;
char dshot_extended_telemetry;
uint16_t send_extended_dshot;
static uint16_t halfpulsetime;

void computeDshotDMA()
{
dshot_frametime = dma_buffer[31] - dma_buffer[0];
halfpulsetime = dshot_frametime >> 5;
if ((dshot_frametime > dshot_frametime_low) && (dshot_frametime < dshot_frametime_high)) {
signaltimeout = 0;
signaltimeout = 0;
for (int i = 0; i < 16; i++) {
// note that dma_buffer[] is uint32_t, we cast the difference to uint16_t to handle
// timer wrap correctly
const uint16_t pdiff = dma_buffer[(i << 1) + 1] - dma_buffer[(i << 1)];
dpulse[i] = (pdiff > halfpulsetime);
const uint16_t pwidth = dma_buffer[(i << 1) + 1] - dma_buffer[(i << 1)];
if (pwidth < (halfpulsetime>>1) || pwidth > (halfpulsetime<<1)) {
// pulse width way off, bad frame
dshot_badcounts++;
return;
}
dpulse[i] = (pwidth > halfpulsetime);
}
uint8_t calcCRC = ((dpulse[0] ^ dpulse[4] ^ dpulse[8]) << 3 | (dpulse[1] ^ dpulse[5] ^ dpulse[9]) << 2 | (dpulse[2] ^ dpulse[6] ^ dpulse[10]) << 1 | (dpulse[3] ^ dpulse[7] ^ dpulse[11]));
uint8_t checkCRC = (dpulse[12] << 3 | dpulse[13] << 2 | dpulse[14] << 1 | dpulse[15]);
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