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DShot bitbang decode - simple refactor (#12688)

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* dshot bitbang decode simple refactor saves about 80 cycles

Co-Authored-By: 4712 <4712@users.noreply.github.com>

* int recommendation

---------

Co-authored-by: 4712 <4712@users.noreply.github.com>
This commit is contained in:
ctzsnooze 2023-05-12 02:41:07 +10:00 • committed by GitHub
parent 10067ad6ad
commit f44cc9fa6e
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1 changed files with 9 additions and 13 deletions
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22
src/main/drivers/dshot_bitbang_decode.c
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@ -32,8 +32,8 @@
#include "drivers/dshot.h" #include "drivers/dshot.h"
#include "drivers/dshot_bitbang_decode.h" #include "drivers/dshot_bitbang_decode.h"
#define MIN_VALID_BBSAMPLES ((21 - 2) * 3) #define MIN_VALID_BBSAMPLES ((21 - 2) * 3) // 57
#define MAX_VALID_BBSAMPLES ((21 + 2) * 3) #define MAX_VALID_BBSAMPLES ((21 + 2) * 3) // 69
// setting this define in dshot.h allows the cli command dshot_telemetry_info to // setting this define in dshot.h allows the cli command dshot_telemetry_info to
// display the received telemetry data in raw form which helps identify // display the received telemetry data in raw form which helps identify
@ -50,7 +50,8 @@ uint16_t bbBuffer[134];
#define BITBAND_SRAM(a,b) ((BITBAND_SRAM_BASE + (((a)-BITBAND_SRAM_REF)<<5) + ((b)<<2))) // Convert SRAM address #define BITBAND_SRAM(a,b) ((BITBAND_SRAM_BASE + (((a)-BITBAND_SRAM_REF)<<5) + ((b)<<2))) // Convert SRAM address
#define DSHOT_TELEMETRY_START_MARGIN 10 #define DSHOT_TELEMETRY_START_MARGIN 10
static uint8_t preambleSkip = 0;
static unsigned int preambleSkip = 0;
typedef struct bitBandWord_s { typedef struct bitBandWord_s {
uint32_t value; uint32_t value;
@ -58,7 +59,6 @@ typedef struct bitBandWord_s {
} bitBandWord_t; } bitBandWord_t;
#ifdef DEBUG_BBDECODE #ifdef DEBUG_BBDECODE
uint32_t sequence[MAX_GCR_EDGES]; uint32_t sequence[MAX_GCR_EDGES];
int sequenceIndex = 0; int sequenceIndex = 0;
@ -106,8 +106,6 @@ static uint32_t decode_bb_value(uint32_t value, uint16_t buffer[], uint32_t coun
uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit) uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
{ {
uint8_t startMargin;
#ifdef DEBUG_BBDECODE #ifdef DEBUG_BBDECODE
memset(sequence, 0, sizeof(sequence)); memset(sequence, 0, sizeof(sequence));
sequenceIndex = 0; sequenceIndex = 0;
@ -132,7 +130,7 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
} }
} }
startMargin = p - b; const unsigned int startMargin = p - b;
DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin); DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin);
if (p >= endP) { if (p >= endP) {
@ -142,7 +140,7 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
return DSHOT_TELEMETRY_NOEDGE; return DSHOT_TELEMETRY_NOEDGE;
} }
int remaining = MIN(count - (p - b), (unsigned int)MAX_VALID_BBSAMPLES); const int remaining = MIN(count - startMargin, (unsigned int)MAX_VALID_BBSAMPLES);
bitBandWord_t* oldP = p; bitBandWord_t* oldP = p;
uint32_t bits = 0; uint32_t bits = 0;
@ -232,7 +230,6 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit) FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
{ {
uint8_t startMargin;
#ifdef DEBUG_BBDECODE #ifdef DEBUG_BBDECODE
memset(sequence, 0, sizeof(sequence)); memset(sequence, 0, sizeof(sequence));
@ -265,7 +262,7 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
} }
} }
startMargin = p - buffer; const unsigned int startMargin = p - buffer;
DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin); DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin);
if (p >= endP) { if (p >= endP) {
@ -277,8 +274,7 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
return DSHOT_TELEMETRY_NOEDGE; return DSHOT_TELEMETRY_NOEDGE;
} }
int remaining = MIN(count - (p - buffer), (unsigned int)MAX_VALID_BBSAMPLES); const int remaining = MIN(count - startMargin, (unsigned int)MAX_VALID_BBSAMPLES);
uint16_t* oldP = p; uint16_t* oldP = p;
uint32_t bits = 0; uint32_t bits = 0;
endP = p + remaining; endP = p + remaining;
@ -300,7 +296,7 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
// A level of length n gets decoded to a sequence of bits of // A level of length n gets decoded to a sequence of bits of
// the form 1000 with a length of (n+1) / 3 to account for 3x // the form 1000 with a length of (n+1) / 3 to account for 3x
// oversampling. // oversampling.
const int len = MAX((p - oldP + 1) / 3,1); const int len = MAX((p - oldP + 1) / 3, 1);
bits += len; bits += len;
value <<= len; value <<= len;
value |= 1 << (len - 1); value |= 1 << (len - 1);