meshtastic · thebentern · Nov 18, 2025 · Sep 6, 2025 · Sep 12, 2025 · Sep 28, 2025
diff --git a/src/Power.cpp b/src/Power.cpp
@@ -194,7 +194,7 @@ static HasBatteryLevel *batteryLevel; // Default to NULL for no battery level se
 
 #ifdef BATTERY_PIN
 
-static void adcEnable()
+void battery_adcEnable()
 {
 #ifdef ADC_CTRL // enable adc voltage divider when we need to read
 #ifdef ADC_USE_PULLUP
@@ -214,7 +214,7 @@ static void adcEnable()
 #endif
 }
 
-static void adcDisable()
+static void battery_adcDisable()
 {
 #ifdef ADC_CTRL // disable adc voltage divider when we need to read
 #ifdef ADC_USE_PULLUP
@@ -320,7 +320,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
             uint32_t raw = 0;
             float scaled = 0;
 
-            adcEnable();
+            battery_adcEnable();
 #ifdef ARCH_ESP32 // ADC block for espressif platforms
             raw = espAdcRead();
             scaled = esp_adc_cal_raw_to_voltage(raw, adc_characs);
@@ -332,7 +332,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
             raw = raw / BATTERY_SENSE_SAMPLES;
             scaled = operativeAdcMultiplier * ((1000 * AREF_VOLTAGE) / pow(2, BATTERY_SENSE_RESOLUTION_BITS)) * raw;
 #endif
-            adcDisable();
+            battery_adcDisable();
 
             if (!initial_read_done) {
                 // Flush the smoothing filter with an ADC reading, if the reading is plausibly correct
@@ -903,13 +903,8 @@ void Power::readPowerStatus()
             low_voltage_counter++;
             LOG_DEBUG("Low voltage counter: %d/10", low_voltage_counter);
             if (low_voltage_counter > 10) {
-#ifdef ARCH_NRF52
-                // We can't trigger deep sleep on NRF52, it's freezing the board
-                LOG_DEBUG("Low voltage detected, but not trigger deep sleep");
-#else
                 LOG_INFO("Low voltage detected, trigger deep sleep");
                 powerFSM.trigger(EVENT_LOW_BATTERY);
-#endif
             }
         } else {
             low_voltage_counter = 0;
@@ -1549,4 +1544,4 @@ bool Power::meshSolarInit()
 {
     return false;
 }
-#endif
+#endif
diff --git a/src/platform/nrf52/main-nrf52.cpp b/src/platform/nrf52/main-nrf52.cpp
@@ -14,6 +14,9 @@
 #include "error.h"
 #include "main.h"
 #include "meshUtils.h"
+#include "power.h"
+
+#include <hal/nrf_lpcomp.h>
 
 #ifdef BQ25703A_ADDR
 #include "BQ25713.h"
@@ -389,6 +392,23 @@ void cpuDeepSleep(uint32_t msecToWake)
         nrf_gpio_cfg_sense_set(BUTTON_PIN, sense);           // Apply SENSE to wake up the device from the deep sleep
 #endif
 
+#ifdef BATTERY_LPCOMP_INPUT
+        // Wake up if power rises again
+        nrf_lpcomp_config_t c;
+        c.reference = BATTERY_LPCOMP_THRESHOLD;
+        c.detection = NRF_LPCOMP_DETECT_UP;
+        c.hyst = NRF_LPCOMP_HYST_NOHYST;
+        nrf_lpcomp_configure(NRF_LPCOMP, &c);
+        nrf_lpcomp_input_select(NRF_LPCOMP, BATTERY_LPCOMP_INPUT);
+        nrf_lpcomp_enable(NRF_LPCOMP);
+
+        battery_adcEnable();
+
+        nrf_lpcomp_task_trigger(NRF_LPCOMP, NRF_LPCOMP_TASK_START);
+        while (!nrf_lpcomp_event_check(NRF_LPCOMP, NRF_LPCOMP_EVENT_READY))
+            ;
+#endif
+
         auto ok = sd_power_system_off();
         if (ok != NRF_SUCCESS) {
             LOG_ERROR("FIXME: Ignoring soft device (EasyDMA pending?) and forcing system-off!");
@@ -420,4 +440,4 @@ void enterDfuMode()
 #else
     enterUf2Dfu();
 #endif
-}
+}
diff --git a/src/power.h b/src/power.h
@@ -143,4 +143,6 @@ class Power : private concurrency::OSThread
 #endif
 };
 
+void battery_adcEnable();
+
 extern Power *power;
diff --git a/variants/nrf52840/heltec_mesh_node_t114/variant.h b/variants/nrf52840/heltec_mesh_node_t114/variant.h
@@ -210,6 +210,16 @@ No longer populated on PCB
 #define VBAT_AR_INTERNAL AR_INTERNAL_3_0
 #define ADC_MULTIPLIER (4.916F)
 
+// rf52840 AIN2 = Pin 4
+#define BATTERY_LPCOMP_INPUT NRF_LPCOMP_INPUT_2
+
+// We have AIN2 with a VBAT divider so AIN2 = VBAT * (100/490)
+// We have the device going deep sleep under 3.1V, which is AIN2 = 0.63V
+// So we can wake up when VBAT>=VDD is restored to 3.3V, where AIN2 = 0.67V
+// Ratio 0.67/3.3 = 0.20, so we can pick a bit higher, 2/8 VDD, which means
+// VBAT=4.04V
+#define BATTERY_LPCOMP_THRESHOLD NRF_LPCOMP_REF_SUPPLY_2_8
+
 #define HAS_RTC 0
 #ifdef __cplusplus
 }

diff --git a/variants/nrf52840/rak4631/variant.h b/variants/nrf52840/rak4631/variant.h
@@ -267,6 +267,20 @@ SO GPIO 39/TXEN MAY NOT BE DEFINED FOR SUCCESSFUL OPERATION OF THE SX1262 - TG
 #define VBAT_AR_INTERNAL AR_INTERNAL_3_0
 #define ADC_MULTIPLIER 1.73
 
+// RAK4630 AIN0 = nrf52840 AIN3 = Pin 5
+#define BATTERY_LPCOMP_INPUT NRF_LPCOMP_INPUT_3
+
+// We have AIN3 with a VBAT divider so AIN3 = VBAT * (1.5/2.5)
+// We have the device going deep sleep under 3.1V, which is AIN3 = 1.86V
+// So we can wake up when VBAT>=VDD is restored to 3.3V, where AIN3 = 1.98V
+// 1.98/3.3 = 6/10, but that's close to the VBAT divider, so we
+// pick 6/8VDD, which means VBAT=4.1V.
+// Reference:
+// VDD=3.3V AIN3=5/8*VDD=2.06V VBAT=1.66*AIN3=3.41V
+// VDD=3.3V AIN3=11/16*VDD=2.26V VBAT=1.66*AIN3=3.76V
+// VDD=3.3V AIN3=6/8*VDD=2.47V VBAT=1.66*AIN3=4.1V
+#define BATTERY_LPCOMP_THRESHOLD NRF_LPCOMP_REF_SUPPLY_11_16
+
 #define HAS_RTC 1
 
 #define HAS_ETHERNET 1
-Original file line number
+Diff line change
@@ Expand Up / @@ -143,4 +143,6 @@ class Power : private concurrency::OSThread @@
     #endif
     };
+    void battery_adcEnable();
     extern Power *power;