仅为三色中性光启用低亮PDM

project/example/ble/ble_peripheral/app/src/bridge_pwm.c

@@ -18,6 +18,7 @@
  * The available OFF time is distributed around both direction changes and
  * each W/C transition retains at least 25 us protection.
  * Normal dual-color output produces one pulse per color per frame (2 kHz).
+ * Only the low-output neutral section of three-color breathing uses PDM.
  */
 #define BRIDGE_PWM_SCALE          1000U
 #define BRIDGE_PWM_PERIOD         6U
@@ -26,8 +27,11 @@
 #define BRIDGE_DEADTIME_US        25U
 #define BRIDGE_DUAL_ACTIVE_US     450U
 #define BRIDGE_MIN_DUAL_PULSE_US  1U
+#define BRIDGE_NEUTRAL_PDM_PULSE_US 50U
 #define BRIDGE_TIMER_TICKS_PER_US 16U
 #define BRIDGE_PDM_THRESHOLD      (BRIDGE_MIX_SCALE * 4096UL)
+#define BRIDGE_NEUTRAL_PDM_THRESHOLD \
+    (BRIDGE_NEUTRAL_PDM_PULSE_US * BRIDGE_PDM_THRESHOLD)
 
 #define BRIDGE_GPIO_PORT          0U
 #define BRIDGE_GPIO_MASK          ((1UL << IO_PWM_W) | (1UL << IO_PWM_C))
@@ -383,6 +387,40 @@ __RAM_CODE void Bridge_Service_1ms(void)
         goto dual_output_ready;
     }
 
+    /*
+     * In the neutral part of three-color breathing, keep each W/C pulse at
+     * a reliable 50 us and reduce only its frame density below that level.
+     * Single-color breathing never enters this branch and stays on hardware
+     * PWM all the way down to zero.
+     */
+    if (deviceStatus != POWEROFF &&
+        Mode == mode1 && choose_mode_falsg == 5U &&
+        w_mix != 0U && c_mix != 0U) {
+        pdm_w_step =
+            BRIDGE_DUAL_ACTIVE_US * ((uint32_t)w_mix << 12);
+        pdm_c_step =
+            BRIDGE_DUAL_ACTIVE_US * ((uint32_t)c_mix << 12);
+
+        if (pdm_w_step < BRIDGE_NEUTRAL_PDM_THRESHOLD &&
+            pdm_c_step < BRIDGE_NEUTRAL_PDM_THRESHOLD) {
+            next_w_us = BRIDGE_NEUTRAL_PDM_PULSE_US;
+            next_c_us = BRIDGE_NEUTRAL_PDM_PULSE_US;
+            total_off_us =
+                BRIDGE_FRAME_US -
+                (2U * BRIDGE_NEUTRAL_PDM_PULSE_US);
+            next_wc_off_us = (uint16_t)(total_off_us / 2U);
+            next_cw_off_us =
+                (uint16_t)(total_off_us - next_wc_off_us);
+            next_pdm_w_step = pdm_w_step;
+            next_pdm_c_step = pdm_c_step;
+            next_pdm_threshold = BRIDGE_NEUTRAL_PDM_THRESHOLD;
+            next_pdm_enabled = 1U;
+            cached_w_mix = (uint16_t)w_mix;
+            cached_c_mix = (uint16_t)c_mix;
+            goto dual_output_ready;
+        }
+    }
+
     if (next_pdm_enabled) {
         cached_w_mix = 0xFFFFU;
         cached_c_mix = 0xFFFFU;