Reduce sender power draw (RX windows + CPU/WiFi/ADC/pins)

- Add LoRa idle/sleep/receive-window helpers and use short RX windows for ACK/time sync

- Schedule sender time-sync windows (fast/slow) and track RX vs sleep time in debug

- Lower sender power (80 MHz CPU, WiFi/BT off, reduced ADC sampling, unused pins pulldown)

- Make SERIAL_DEBUG_MODE a build flag, add prod envs with debug off, and document changes

README.md

@@ -256,6 +256,7 @@ inline constexpr uint16_t EXPECTED_SENDER_IDS[NUM_SENDERS] = { 0xF19C };
   - 3.0 V = 0%
   - 4.2 V = 100%
 - Uses deep sleep between cycles (`SENDER_WAKE_INTERVAL_SEC`).
+- Sender CPU is throttled to 80 MHz and LoRa RX is only enabled in short windows (ACK wait or time-sync).
 
 ## Web UI
 - AP SSID: `DD3-Bridge-<short_id>` (prefix configurable)
@@ -296,12 +297,14 @@ inline constexpr uint16_t EXPECTED_SENDER_IDS[NUM_SENDERS] = { 0xF19C };
 - When no RTC is present or enabled, the receiver keeps sending time sync every 60 seconds.
 
 ## Build Environments
-- `lilygo-t3-v1-6-1`: production build
+- `lilygo-t3-v1-6-1`: production build (debug on)
 - `lilygo-t3-v1-6-1-test`: test build with `ENABLE_TEST_MODE`
-- `lilygo-t3-v1-6-1-868`: production build for 868 MHz modules
+- `lilygo-t3-v1-6-1-868`: production build for 868 MHz modules (debug on)
 - `lilygo-t3-v1-6-1-868-test`: test build for 868 MHz modules
 - `lilygo-t3-v1-6-1-payload-test`: build with `PAYLOAD_CODEC_TEST`
 - `lilygo-t3-v1-6-1-868-payload-test`: 868 MHz build with `PAYLOAD_CODEC_TEST`
+- `lilygo-t3-v1-6-1-prod`: production build with serial debug off
+- `lilygo-t3-v1-6-1-868-prod`: 868 MHz production build with serial debug off
 
 ## Config Knobs
 Key timing settings in `include/config.h`:
@@ -311,9 +314,11 @@ Key timing settings in `include/config.h`:
 - `BATCH_MAX_RETRIES`
  - `BATCH_QUEUE_DEPTH`
  - `BATCH_RETRY_POLICY` (keep or drop on retry exhaustion)
- - `SERIAL_DEBUG_MODE` / `SERIAL_DEBUG_DUMP_JSON`
+ - `SERIAL_DEBUG_MODE_FLAG` (build flag) / `SERIAL_DEBUG_DUMP_JSON`
  - `LORA_SEND_BYPASS` (debug only)
  - `ENABLE_SD_LOGGING` / `PIN_SD_CS`
+ - `SENDER_TIMESYNC_WINDOW_MS`
+ - `SENDER_TIMESYNC_CHECK_SEC_FAST` / `SENDER_TIMESYNC_CHECK_SEC_SLOW`
  - `SD_HISTORY_MAX_DAYS` / `SD_HISTORY_MIN_RES_MIN`
  - `SD_HISTORY_MAX_BINS` / `SD_HISTORY_TIME_BUDGET_MS`
  - `WEB_AUTH_REQUIRE_STA` / `WEB_AUTH_REQUIRE_AP` / `WEB_AUTH_DEFAULT_USER` / `WEB_AUTH_DEFAULT_PASS`

include/config.h

@@ -60,6 +60,9 @@ constexpr uint32_t SENDER_WAKE_INTERVAL_SEC = 30;
 constexpr uint32_t TIME_SYNC_INTERVAL_SEC = 60;
 constexpr uint32_t TIME_SYNC_SLOW_INTERVAL_SEC = 3600;
 constexpr uint32_t TIME_SYNC_FAST_WINDOW_MS = 10UL * 60UL * 1000UL;
+constexpr uint32_t SENDER_TIMESYNC_WINDOW_MS = 300;
+constexpr uint32_t SENDER_TIMESYNC_CHECK_SEC_FAST = 60;
+constexpr uint32_t SENDER_TIMESYNC_CHECK_SEC_SLOW = 3600;
 constexpr bool ENABLE_DS3231 = true;
 constexpr uint32_t OLED_PAGE_INTERVAL_MS = 4000;
 constexpr uint32_t OLED_AUTO_OFF_MS = 10UL * 60UL * 1000UL;
@@ -73,7 +76,10 @@ constexpr uint8_t BATCH_QUEUE_DEPTH = 10;
 constexpr BatchRetryPolicy BATCH_RETRY_POLICY = BatchRetryPolicy::Keep;
 constexpr uint32_t WATCHDOG_TIMEOUT_SEC = 120;
 constexpr bool ENABLE_HA_DISCOVERY = true;
-constexpr bool SERIAL_DEBUG_MODE = true;
+#ifndef SERIAL_DEBUG_MODE_FLAG
+#define SERIAL_DEBUG_MODE_FLAG 0
+#endif
+constexpr bool SERIAL_DEBUG_MODE = SERIAL_DEBUG_MODE_FLAG != 0;
 constexpr bool SERIAL_DEBUG_DUMP_JSON = false;
 constexpr bool LORA_SEND_BYPASS = false;
 constexpr bool ENABLE_SD_LOGGING = true;

include/lora_transport.h

@@ -19,5 +19,7 @@ struct LoraPacket {
 void lora_init();
 bool lora_send(const LoraPacket &pkt);
 bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms);
+void lora_idle();
 void lora_sleep();
+bool lora_receive_window(LoraPacket &pkt, uint32_t timeout_ms);
 uint32_t lora_airtime_ms(size_t packet_len);

include/power_manager.h

@@ -5,6 +5,7 @@
 
 void power_sender_init();
 void power_receiver_init();
+void power_configure_unused_pins_sender();
 void read_battery(MeterData &data);
 uint8_t battery_percent_from_voltage(float voltage_v);
 void light_sleep_ms(uint32_t ms);

platformio.ini

@@ -18,6 +18,8 @@ lib_deps =
   adafruit/Adafruit SSD1306@^2.5.9
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
 
 [env:lilygo-t3-v1-6-1-test]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
@@ -30,6 +32,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DENABLE_TEST_MODE
 
 [env:lilygo-t3-v1-6-1-868]
@@ -43,6 +46,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DLORA_FREQUENCY_HZ=868E6
 
 [env:lilygo-t3-v1-6-1-868-test]
@@ -56,6 +60,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DENABLE_TEST_MODE
   -DLORA_FREQUENCY_HZ=868E6
 
@@ -70,6 +75,7 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DPAYLOAD_CODEC_TEST
 
 [env:lilygo-t3-v1-6-1-868-payload-test]
@@ -83,5 +89,33 @@ lib_deps =
   adafruit/Adafruit GFX Library@^1.11.9
   knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
   -DPAYLOAD_CODEC_TEST
   -DLORA_FREQUENCY_HZ=868E6
+
+[env:lilygo-t3-v1-6-1-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+
+[env:lilygo-t3-v1-6-1-868-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+  -DLORA_FREQUENCY_HZ=868E6

src/lora_transport.cpp

@@ -110,10 +110,24 @@ bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms) {
   }
 }
 
+void lora_idle() {
+  LoRa.idle();
+}
+
 void lora_sleep() {
   LoRa.sleep();
 }
 
+bool lora_receive_window(LoraPacket &pkt, uint32_t timeout_ms) {
+  if (timeout_ms == 0) {
+    return false;
+  }
+  LoRa.receive();
+  bool got = lora_receive(pkt, timeout_ms);
+  LoRa.sleep();
+  return got;
+}
+
 uint32_t lora_airtime_ms(size_t packet_len) {
   if (packet_len == 0) {
     return 0;

src/main.cpp

@@ -88,6 +88,10 @@ static uint8_t g_inflight_count = 0;
 static uint16_t g_inflight_batch_id = 0;
 static bool g_inflight_active = false;
 static uint32_t g_last_debug_log_ms = 0;
+static uint32_t g_sender_last_timesync_check_ms = 0;
+static uint32_t g_sender_rx_window_ms = 0;
+static uint32_t g_sender_sleep_ms = 0;
+static uint32_t g_sender_power_log_ms = 0;
 
 static void watchdog_kick();
 
@@ -144,6 +148,22 @@ static void update_battery_cache() {
   g_last_battery_ms = millis();
 }
 
+static bool sender_timesync_window_due() {
+  uint32_t interval_sec = SENDER_TIMESYNC_CHECK_SEC_FAST;
+  if (time_is_synced() && time_rtc_present()) {
+    interval_sec = SENDER_TIMESYNC_CHECK_SEC_SLOW;
+  }
+  if (g_sender_last_timesync_check_ms == 0) {
+    g_sender_last_timesync_check_ms = millis() - interval_sec * 1000UL;
+  }
+  uint32_t now_ms = millis();
+  if (now_ms - g_sender_last_timesync_check_ms >= interval_sec * 1000UL) {
+    g_sender_last_timesync_check_ms = now_ms;
+    return true;
+  }
+  return false;
+}
+
 static bool batch_queue_drop_oldest() {
   if (g_batch_count == 0) {
     return false;
@@ -620,6 +640,7 @@ void setup() {
 
   if (g_role == DeviceRole::Sender) {
     power_sender_init();
+    power_configure_unused_pins_sender();
     meter_init();
     g_last_sample_ms = millis() - METER_SAMPLE_INTERVAL_MS;
     g_last_send_ms = millis();
@@ -712,37 +733,18 @@ static void sender_loop() {
   }
 
   if (g_batch_ack_pending) {
-    uint32_t end_ms = millis() + 400;
+    LoraPacket ack_pkt = {};
-    while (millis() < end_ms) {
+    uint32_t rx_start = millis();
-      LoraPacket ack_pkt = {};
+    bool got_ack = lora_receive_window(ack_pkt, 400);
-      if (!lora_receive(ack_pkt, 0) || ack_pkt.protocol_version != PROTOCOL_VERSION) {
+    uint32_t rx_elapsed = millis() - rx_start;
-        delay(5);
+    if (SERIAL_DEBUG_MODE) {
-        continue;
+      g_sender_rx_window_ms += rx_elapsed;
-      }
-      if (ack_pkt.payload_type == PayloadType::Ack && ack_pkt.payload_len >= 6 && ack_pkt.role == DeviceRole::Receiver) {
-        uint16_t ack_id = read_u16_le(ack_pkt.payload);
-        uint16_t ack_sender = read_u16_le(&ack_pkt.payload[2]);
-        uint16_t ack_receiver = read_u16_le(&ack_pkt.payload[4]);
-        if (ack_sender == g_short_id && ack_receiver == ack_pkt.device_id_short &&
-            g_batch_ack_pending && ack_id == g_last_sent_batch_id) {
-          g_last_acked_batch_id = ack_id;
-          serial_debug_printf("ack: ok batch_id=%u", ack_id);
-          finish_inflight_batch();
-          break;
-        }
-      }
     }
-  }
+    if (got_ack && ack_pkt.payload_type == PayloadType::Ack && ack_pkt.payload_len >= 6 && ack_pkt.role == DeviceRole::Receiver) {
-
+      uint16_t ack_id = read_u16_le(ack_pkt.payload);
-  LoraPacket rx = {};
+      uint16_t ack_sender = read_u16_le(&ack_pkt.payload[2]);
-  if (lora_receive(rx, 0) && rx.protocol_version == PROTOCOL_VERSION) {
+      uint16_t ack_receiver = read_u16_le(&ack_pkt.payload[4]);
-    if (rx.payload_type == PayloadType::TimeSync) {
+      if (ack_sender == g_short_id && ack_receiver == ack_pkt.device_id_short &&
-      time_handle_timesync_payload(rx.payload, rx.payload_len);
-    } else if (rx.payload_type == PayloadType::Ack && rx.payload_len >= 6 && rx.role == DeviceRole::Receiver) {
-      uint16_t ack_id = read_u16_le(rx.payload);
-      uint16_t ack_sender = read_u16_le(&rx.payload[2]);
-      uint16_t ack_receiver = read_u16_le(&rx.payload[4]);
-      if (ack_sender == g_short_id && ack_receiver == rx.device_id_short &&
           g_batch_ack_pending && ack_id == g_last_sent_batch_id) {
         g_last_acked_batch_id = ack_id;
         serial_debug_printf("ack: ok batch_id=%u", ack_id);
@@ -751,6 +753,23 @@ static void sender_loop() {
     }
   }
 
+  bool timesync_due = (!g_batch_ack_pending && sender_timesync_window_due());
+  if (timesync_due) {
+    LoraPacket rx = {};
+    uint32_t rx_start = millis();
+    bool got = lora_receive_window(rx, SENDER_TIMESYNC_WINDOW_MS);
+    uint32_t rx_elapsed = millis() - rx_start;
+    if (SERIAL_DEBUG_MODE) {
+      g_sender_rx_window_ms += rx_elapsed;
+    }
+    if (got && rx.payload_type == PayloadType::TimeSync) {
+      time_handle_timesync_payload(rx.payload, rx.payload_len);
+    }
+  }
+  if (!g_batch_ack_pending) {
+    lora_sleep();
+  }
+
   if (g_batch_ack_pending && (now_ms - g_last_batch_send_ms >= g_batch_ack_timeout_ms)) {
     if (g_batch_retry_count < BATCH_MAX_RETRIES) {
       g_batch_retry_count++;
@@ -780,6 +799,15 @@ static void sender_loop() {
   uint32_t next_due = next_sample_due < next_send_due ? next_sample_due : next_send_due;
   if (!g_batch_ack_pending && next_due > now_ms) {
     watchdog_kick();
+    if (SERIAL_DEBUG_MODE) {
+      g_sender_sleep_ms += (next_due - now_ms);
+      if (now_ms - g_sender_power_log_ms >= 10000) {
+        g_sender_power_log_ms = now_ms;
+        serial_debug_printf("power: rx_ms=%lu sleep_ms=%lu", static_cast<unsigned long>(g_sender_rx_window_ms),
+                            static_cast<unsigned long>(g_sender_sleep_ms));
+      }
+    }
+    lora_sleep();
     light_sleep_ms(next_due - now_ms);
   }
 }

src/power_manager.cpp

@@ -10,7 +10,10 @@ static constexpr float BATTERY_CAL = 1.0f;
 static constexpr float ADC_REF_V = 3.3f;
 
 void power_sender_init() {
+  setCpuFrequencyMhz(80);
+  WiFi.mode(WIFI_OFF);
   esp_wifi_stop();
+  esp_wifi_deinit();
   btStop();
   analogReadResolution(12);
   pinMode(PIN_BAT_ADC, INPUT);
@@ -22,14 +25,19 @@ void power_receiver_init() {
   pinMode(PIN_BAT_ADC, INPUT);
 }
 
-void read_battery(MeterData &data) {
+void power_configure_unused_pins_sender() {
-  const int samples = 8;
+  // Board-specific: only touch pins that are known unused and safe on TTGO LoRa32 v1.6.1
-  uint32_t sum = 0;
+  const uint8_t pins[] = {32, 33};
-  for (int i = 0; i < samples; ++i) {
+  for (uint8_t pin : pins) {
-    sum += analogRead(PIN_BAT_ADC);
+    pinMode(pin, INPUT_PULLDOWN);
-    delay(5);
   }
-  float avg = static_cast<float>(sum) / samples;
+}
+
+void read_battery(MeterData &data) {
+  uint32_t sum = 0;
+  sum += analogRead(PIN_BAT_ADC);
+  sum += analogRead(PIN_BAT_ADC);
+  float avg = static_cast<float>(sum) / 2.0f;
   float v = (avg / 4095.0f) * ADC_REF_V * BATTERY_DIVIDER * BATTERY_CAL;
 
   data.battery_voltage_v = v;