From c8e61243008ea9f74fb6b744407fd5c629058d4a Mon Sep 17 00:00:00 2001
From: Mark Haslinghuis <mark@numloq.nl>
Date: Mon, 17 Jul 2023 22:51:25 +0200
Subject: [PATCH] [MAINT] Add dshot_telemetry_start_margin setting (#12912)
 (#12964)

---
 src/main/cli/settings.c                 |  1 +
 src/main/drivers/dshot_bitbang_decode.c | 17 ++++++++++++++---
 src/main/pg/motor.c                     | 19 ++++++++++++++++++-
 src/main/pg/motor.h                     |  1 +
 4 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/src/main/cli/settings.c b/src/main/cli/settings.c
index 1aaba47b692..ee895408aeb 100644
--- a/src/main/cli/settings.c
+++ b/src/main/cli/settings.c
@@ -847,6 +847,7 @@ 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
index 591436cdeea..8b723acd84b 100644
--- a/src/main/drivers/dshot_bitbang_decode.c
+++ b/src/main/drivers/dshot_bitbang_decode.c
@@ -49,7 +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 {
@@ -220,7 +219,13 @@ 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;
@@ -330,7 +335,13 @@ 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
index 3f70786fd0c..1707c64d96e 100644
--- a/src/main/pg/motor.c
+++ b/src/main/pg/motor.c
@@ -33,7 +33,23 @@
 #include "pg/pg_ids.h"
 #include "pg/motor.h"
 
-PG_REGISTER_WITH_RESET_FN(motorConfig_t, motorConfig, PG_MOTOR_CONFIG, 1);
+#if !defined(DEFAULT_DSHOT_BITBANG)
+#define DEFAULT_DSHOT_BITBANG DSHOT_BITBANG_AUTO
+#endif
+
+#if !defined(DSHOT_BITBANGED_TIMER_DEFAULT)
+#define DSHOT_BITBANGED_TIMER_DEFAULT DSHOT_BITBANGED_TIMER_AUTO
+#endif
+
+#if !defined(DEFAULT_DSHOT_BURST)
+#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)
 {
@@ -81,6 +97,7 @@ void pgResetFn_motorConfig(motorConfig_t *motorConfig)
 #ifdef USE_DSHOT_BITBANG
     motorConfig->dev.useDshotBitbang = DSHOT_BITBANG_DEFAULT;
     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
index a2ea0fb5515..929b4195676 100644
--- 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 {