Remove dshot_telemetry_start_margin setting to use auto-tune(#13075) (#13082)

src/main/cli/settings.c

@@ -847,7 +847,6 @@ 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) },

src/main/drivers/dshot_bitbang_decode.c

@@ -31,6 +31,7 @@
 #include "build/debug.h"
 #include "drivers/dshot.h"
 #include "drivers/dshot_bitbang_decode.h"
+#include "drivers/time.h"
 
 #define MIN_VALID_BBSAMPLES ((21 - 2) * 3)
 #define MAX_VALID_BBSAMPLES ((21 + 2) * 3)
@@ -49,6 +50,15 @@ 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
 
+// Period at which to check preamble length
+#define MARGIN_CHECK_INTERVAL_US 500000
+
+// Target 5 clock cycles of input data ahead of leading edge
+#define DSHOT_TELEMETRY_START_MARGIN 5
+
+static uint32_t minMargin = UINT32_MAX;
+static timeUs_t nextMarginCheckUs = 0;
+
 static uint8_t preambleSkip = 0;
 
 typedef struct bitBandWord_s {
@@ -102,11 +112,10 @@ static uint32_t decode_bb_value(uint32_t value, uint16_t buffer[], uint32_t coun
     return value;
 }
 
-
+#ifdef USE_DSHOT_BITBAND
 uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
 {
-    uint8_t startMargin;
-
+    timeUs_t now = micros();
 #ifdef DEBUG_BBDECODE
     memset(sequence, 0, sizeof(sequence));
     sequenceIndex = 0;
@@ -120,6 +129,8 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
     // Jump forward in the buffer to just before where we anticipate the first zero
     p += preambleSkip;
 
+    DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, preambleSkip);
+
     // Eliminate leading high signal level by looking for first zero bit in data stream.
     // Manual loop unrolling and branch hinting to produce faster code.
     while (p < endP) {
@@ -131,13 +142,16 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
         }
     }
 
-    startMargin = p - b;
-    DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin);
+    const uint32_t startMargin = p - b;
 
     if (p >= endP) {
         // not returning telemetry is ok if the esc cpu is
         // overburdened.  in that case no edge will be found and
         // BB_NOEDGE indicates the condition to caller
+        if (preambleSkip > 0) {
+            // Increase the start margin
+            preambleSkip--;
+        }
         return DSHOT_TELEMETRY_NOEDGE;
     }
 
@@ -203,6 +217,7 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
         }
     }
 
+    // length of last sequence has to be inferred since the last bit with inverted dshot is high
     if (bits < 18) {
         return DSHOT_TELEMETRY_NOEDGE;
     }
@@ -213,20 +228,34 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
         return DSHOT_TELEMETRY_NOEDGE;
     }
 
+    // Data appears valid
+    if (startMargin < minMargin) {
+        minMargin = startMargin;
+    }
+
+    if (cmpTimeUs(now, nextMarginCheckUs) >= 0) {
+        nextMarginCheckUs += MARGIN_CHECK_INTERVAL_US;
+
+        // Handle a skipped check
+        if (nextMarginCheckUs < now) {
+            nextMarginCheckUs = now + DSHOT_TELEMETRY_START_MARGIN;
+        }
+
+        if (minMargin > DSHOT_TELEMETRY_START_MARGIN) {
+            preambleSkip = minMargin - DSHOT_TELEMETRY_START_MARGIN;
+        } else {
+            preambleSkip = 0;
+        }
+
+        minMargin = UINT32_MAX;
+    }
+
 #ifdef DEBUG_BBDECODE
     sequence[sequenceIndex] = sequence[sequenceIndex] + (nlen) * 3;
     sequenceIndex++;
 #endif
 
     // The anticipated edges were observed
-
-    // 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;
         value |= 1 << (nlen - 1);
@@ -235,10 +264,11 @@ uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit)
     return decode_bb_value(value, buffer, count, bit);
 }
 
+#else // USE_DSHOT_BITBAND
+
 FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
 {
-    uint8_t startMargin;
-
+    timeUs_t now = micros();
 #ifdef DEBUG_BBDECODE
     memset(sequence, 0, sizeof(sequence));
     sequenceIndex = 0;
@@ -259,6 +289,8 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
     // Jump forward in the buffer to just before where we anticipate the first zero
     p += preambleSkip;
 
+    DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, preambleSkip);
+
     // Eliminate leading high signal level by looking for first zero bit in data stream.
     // Manual loop unrolling and branch hinting to produce faster code.
     while (p < endP) {
@@ -269,16 +301,17 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
             break;
         }
     }
-
-    startMargin = p - buffer;
-    DEBUG_SET(DEBUG_DSHOT_TELEMETRY_COUNTS, 3, startMargin);
+    const uint32_t startMargin = p - buffer;
 
     if (p >= endP) {
         // not returning telemetry is ok if the esc cpu is
         // overburdened.  in that case no edge will be found and
         // BB_NOEDGE indicates the condition to caller
         // Increase the start margin
-        preambleSkip--;
+        if (preambleSkip > 0) {
+            // Increase the start margin
+            preambleSkip--;
+        }
         return DSHOT_TELEMETRY_NOEDGE;
     }
 
@@ -317,32 +350,43 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
 
     // length of last sequence has to be inferred since the last bit with inverted dshot is high
     if (bits < 18) {
-        // Increase the start margin
-        preambleSkip--;
         return DSHOT_TELEMETRY_NOEDGE;
     }
 
+    // length of last sequence has to be inferred since the last bit with inverted dshot is high
     const int nlen = 21 - bits;
+    if (nlen < 0) {
+        return DSHOT_TELEMETRY_NOEDGE;
+    }
+
+    // Data appears valid
+    if (startMargin < minMargin) {
+        minMargin = startMargin;
+    }
+
+    if (cmpTimeUs(now, nextMarginCheckUs) >= 0) {
+        nextMarginCheckUs += MARGIN_CHECK_INTERVAL_US;
+
+        // Handle a skipped check
+        if (nextMarginCheckUs < now) {
+            nextMarginCheckUs = now + DSHOT_TELEMETRY_START_MARGIN;
+        }
+
+        if (minMargin > DSHOT_TELEMETRY_START_MARGIN) {
+            preambleSkip = minMargin - DSHOT_TELEMETRY_START_MARGIN;
+        } else {
+            preambleSkip = 0;
+        }
+
+        minMargin = UINT32_MAX;
+    }
+
 #ifdef DEBUG_BBDECODE
     sequence[sequenceIndex] = sequence[sequenceIndex] + (nlen) * 3;
     sequenceIndex++;
 #endif
 
-    if (nlen < 0) {
-        // Increase the start margin
-        preambleSkip--;
-        return DSHOT_TELEMETRY_NOEDGE;
-    }
-
     // The anticipated edges were observed
-
-    // 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;
         value |= 1 << (nlen - 1);
@@ -350,5 +394,6 @@ FAST_CODE uint32_t decode_bb( uint16_t buffer[], uint32_t count, uint32_t bit)
 
     return decode_bb_value(value, buffer, count, bit);
 }
+#endif // USE_DSHOT_BITBAND
 
 #endif

src/main/drivers/dshot_bitbang_decode.h

@@ -18,14 +18,14 @@
  * If not, see <http://www.gnu.org/licenses/>.
  */
 
-
+#include "platform.h"
 
 #if defined(USE_DSHOT) && defined(USE_DSHOT_TELEMETRY)
 
-
-
-uint32_t decode_bb(uint16_t buffer[], uint32_t count, uint32_t mask);
+#ifdef USE_DSHOT_BITBAND
 uint32_t decode_bb_bitband( uint16_t buffer[], uint32_t count, uint32_t bit);
-
+#else
+uint32_t decode_bb(uint16_t buffer[], uint32_t count, uint32_t mask);
+#endif
 
 #endif

src/main/pg/motor.c

@@ -45,10 +45,6 @@
 #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)
@@ -97,7 +93,6 @@ 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
 }
 

src/main/pg/motor.h

@@ -50,7 +50,6 @@ 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 {

src/main/target/STM32F405/target.h

@@ -57,6 +57,8 @@
 #define USE_I2C
 #define I2C_FULL_RECONFIGURABILITY
 
+#define USE_DSHOT_BITBAND
+
 #define USE_BEEPER
 
 #define USE_SPI

src/main/target/STM32F411/target.h

@@ -49,6 +49,8 @@
 #define USE_I2C
 #define I2C_FULL_RECONFIGURABILITY
 
+#define USE_DSHOT_BITBAND
+
 #define USE_BEEPER
 
 #ifdef USE_SDCARD