piezo power on/off 시점 조정(전력 절감)

- on 구간 최소화

src/command/handlers/cmd_piezo.c

@@ -64,7 +64,11 @@ int cmd_mbb(const uint8_t *data, uint8_t data_len)
         cmd_send_response_bundle((uint16_t)batt_mv, accel, gyro, temp_cdeg);
 
         DBG_PRINTF("[MBB] piezo sweep start\r\n");
+
         status = piezo_measure_sweep();
+
+        piezo_power_off();
+        
         if (status == ECHO_STATUS_OK)
         {
             for (uint8_t ch = 0; ch < PIEZO_NUM_CHANNELS; ch++)
@@ -75,7 +79,7 @@ int cmd_mbb(const uint8_t *data, uint8_t data_len)
         }
     }
 
-    piezo_power_off();
+    
     DBG_PRINTF("[MBB] done\r\n");
     cmd_send_response_u16("raa:", (uint16_t)status); // 최종 상태 raa: 전송
     DBG_PRINTF("[CMD] mbb status=0x%04X\r\n", status);
@@ -123,6 +127,9 @@ int cmd_mtb(const uint8_t *data, uint8_t data_len)
     {
         DBG_PRINTF("[MTB] piezo sweep start\r\n");
         status = piezo_measure_sweep();
+
+        piezo_power_off();
+
         if (status == ECHO_STATUS_OK)
         {
             for (uint8_t ch = 0; ch < PIEZO_NUM_CHANNELS; ch++)
@@ -157,7 +164,6 @@ int cmd_mtb(const uint8_t *data, uint8_t data_len)
     }
     DBG_PRINTF("[CMD] mtb status=0x%04X\r\n", status);
 
-    piezo_power_off();
     DBG_PRINTF("[CMD] mtb status=0x%04X rim=%u\r\n", status, rim_count);
 
     processing = false;

src/measurement/piezo_measure.c

@@ -167,9 +167,6 @@ int piezo_measure_start_session(void)
         return ECHO_STATUS_PIEZO;
     }
 
-    piezo_power_on();
-    k_msleep(PIEZO_POWER_STABILIZE_MS);
-
     err = echo_adc_init();
     if (err)
     {
@@ -233,6 +230,9 @@ int piezo_measure_sweep(void)
         
         if (ch == 0U) // 채널 0 시작 전에만 dummy burst + ADC capture 수행
         {
+            piezo_power_on();
+            k_msleep(PIEZO_POWER_STABILIZE_MS);
+
             // Dummy burst + ADC caputre
             /*
             for (uint8_t dummy = 0; dummy < PIEZO_DUMMY_CAPTURE_COUNT; dummy++)