Add dshot_telemetry_start_margin setting (betaflight#12912)

freasy · Jul 19, 2023 · 50a5d2d · 50a5d2d
1 parent 76a7636
commit 50a5d2d
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Showing 4 changed files with 21 additions and 4 deletions.
diff --git a/src/main/cli/settings.c b/src/main/cli/settings.c
@@ -859,6 +859,7 @@ const clivalue_t valueTable[] = {
 #ifdef USE_DSHOT_BITBANG
     { "dshot_bitbang",               VAR_UINT8  | HARDWARE_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON_AUTO }, PG_MOTOR_CONFIG, offsetof(motorConfig_t, dev.useDshotBitbang) },
     { "dshot_bitbang_timer",         VAR_UINT8  | HARDWARE_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_DSHOT_BITBANGED_TIMER }, PG_MOTOR_CONFIG, offsetof(motorConfig_t, dev.useDshotBitbangedTimer) },
+    { "dshot_telemetry_start_margin", VAR_UINT8  | HARDWARE_VALUE , .config.minmaxUnsigned = { 0, 100 }, PG_MOTOR_CONFIG, offsetof(motorConfig_t, dev.telemetryStartMargin) },
 #endif
 #endif
     { PARAM_NAME_USE_UNSYNCED_PWM,  VAR_UINT8  | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON }, PG_MOTOR_CONFIG, offsetof(motorConfig_t, dev.useUnsyncedPwm) },

diff --git a/src/main/drivers/dshot_bitbang_decode.c b/src/main/drivers/dshot_bitbang_decode.c
@@ -49,8 +49,6 @@ uint16_t bbBuffer[134];
 #define BITBAND_SRAM_BASE  0x22000000
 #define BITBAND_SRAM(a,b) ((BITBAND_SRAM_BASE + (((a)-BITBAND_SRAM_REF)<<5) + ((b)<<2)))  // Convert SRAM address
 
-#define DSHOT_TELEMETRY_START_MARGIN 10
-
 static uint8_t preambleSkip = 0;
 
 typedef struct bitBandWord_s {
@@ -217,7 +215,13 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
 #endif
 
     // The anticipated edges were observed
-    preambleSkip = startMargin - DSHOT_TELEMETRY_START_MARGIN;
+
+    // Attempt to skip the preamble ahead of the telemetry to save CPU
+    if (startMargin > motorConfig()->dev.telemetryStartMargin) {
+        preambleSkip = startMargin - motorConfig()->dev.telemetryStartMargin;
+    } else {
+        preambleSkip = 0;
+    }
 
     if (nlen > 0) {
         value <<= nlen;
@@ -325,7 +329,13 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
     }
 
     // The anticipated edges were observed
-    preambleSkip = startMargin - DSHOT_TELEMETRY_START_MARGIN;
+
+    // Attempt to skip the preamble ahead of the telemetry to save CPU
+    if (startMargin > motorConfig()->dev.telemetryStartMargin) {
+        preambleSkip = startMargin - motorConfig()->dev.telemetryStartMargin;
+    } else {
+        preambleSkip = 0;
+    }
 
     if (nlen > 0) {
         value <<= nlen;

diff --git a/src/main/pg/motor.c b/src/main/pg/motor.c
@@ -44,6 +44,10 @@
 #define DEFAULT_DSHOT_BURST DSHOT_DMAR_OFF
 #endif
 
+#if !defined(DSHOT_TELEMETRY_START_MARGIN)
+#define DSHOT_TELEMETRY_START_MARGIN 10
+#endif
+
 PG_REGISTER_WITH_RESET_FN(motorConfig_t, motorConfig, PG_MOTOR_CONFIG, 2);
 
 void pgResetFn_motorConfig(motorConfig_t *motorConfig)
@@ -110,6 +114,7 @@ void pgResetFn_motorConfig(motorConfig_t *motorConfig)
 #ifdef USE_DSHOT_BITBANG
     motorConfig->dev.useDshotBitbang = DEFAULT_DSHOT_BITBANG;
     motorConfig->dev.useDshotBitbangedTimer = DSHOT_BITBANGED_TIMER_DEFAULT;
+    motorConfig->dev.telemetryStartMargin = DSHOT_TELEMETRY_START_MARGIN;
 #endif
 }
 

diff --git a/src/main/pg/motor.h b/src/main/pg/motor.h
@@ -50,6 +50,7 @@ typedef struct motorDevConfig_s {
     uint8_t  useDshotBitbang;
     uint8_t  useDshotBitbangedTimer;
     uint8_t  motorOutputReordering[MAX_SUPPORTED_MOTORS]; // Reindexing motors for "remap motors" feature in Configurator
+    uint8_t  telemetryStartMargin;
 } motorDevConfig_t;
 
 typedef struct motorConfig_s {