From afd4c333587a7714731dea9b18cea81bea21660a Mon Sep 17 00:00:00 2001
From: Wessel Nieboer <wessel@weebl.me>
Date: Mon, 2 Mar 2026 15:10:43 +0100
Subject: [PATCH] Fix RAK4631 boot issue

Wait 50ms after boot before actually shutting down on low voltage

Also fix deadlock issue where only USB can wake the device
---
 src/helpers/NRF52Board.cpp             | 25 +++++++++++++++++++++----
 src/helpers/NRF52Board.h               |  2 +-
 variants/heltec_t114/T114Board.cpp     |  4 +++-
 variants/rak4631/RAK4631Board.cpp      |  4 +++-
 variants/xiao_nrf52/XiaoNrf52Board.cpp |  4 +++-
 5 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/helpers/NRF52Board.cpp b/src/helpers/NRF52Board.cpp
index 23f7cafc..0a629d22 100644
--- a/src/helpers/NRF52Board.cpp
+++ b/src/helpers/NRF52Board.cpp
@@ -117,10 +117,17 @@ bool NRF52Board::checkBootVoltage(const PowerMgtConfig* config) {
   // Only trigger shutdown if reading is valid (>1000mV) AND below threshold
   // This prevents spurious shutdowns on ADC glitches or uninitialized reads
   if (boot_voltage_mv > 1000 && boot_voltage_mv < config->voltage_bootlock) {
-    MESH_DEBUG_PRINTLN("PWRMGT: Boot voltage too low - entering protective shutdown");
+    // First reading below threshold - wait for DCDC to stabilize and re-read
+    delay(50);
+    boot_voltage_mv = getBattMilliVolts();
+    MESH_DEBUG_PRINTLN("PWRMGT: Boot voltage (confirmed) = %u mV (threshold = %u mV)",
+        boot_voltage_mv, config->voltage_bootlock);
 
-    initiateShutdown(SHUTDOWN_REASON_BOOT_PROTECT);
-    return false;  // Should never reach this
+    if (boot_voltage_mv > 1000 && boot_voltage_mv < config->voltage_bootlock) {
+      MESH_DEBUG_PRINTLN("PWRMGT: Boot voltage too low - entering protective shutdown");
+      initiateShutdown(SHUTDOWN_REASON_BOOT_PROTECT);
+      return false;  // Should never reach this
+    }
   }
 
   return true;
@@ -164,7 +171,7 @@ void NRF52Board::enterSystemOff(uint8_t reason) {
   NVIC_SystemReset();
 }
 
-void NRF52Board::configureVoltageWake(uint8_t ain_channel, uint8_t refsel) {
+bool NRF52Board::configureVoltageWake(uint8_t ain_channel, uint8_t refsel) {
   // LPCOMP is not managed by SoftDevice - direct register access required
   // Halt and disable before reconfiguration
   NRF_LPCOMP->TASKS_STOP = 1;
@@ -200,6 +207,14 @@ void NRF52Board::configureVoltageWake(uint8_t ain_channel, uint8_t refsel) {
     delayMicroseconds(50);
   }
 
+  // Safety: if voltage is already above threshold, UP detection will never fire
+  if (NRF_LPCOMP->RESULT & LPCOMP_RESULT_RESULT_Msk) {
+    MESH_DEBUG_PRINTLN("PWRMGT: LPCOMP shows voltage above threshold - unsafe for SYSTEMOFF");
+    NRF_LPCOMP->TASKS_STOP = 1;
+    NRF_LPCOMP->ENABLE = LPCOMP_ENABLE_ENABLE_Disabled;
+    return false;
+  }
+
   if (refsel == 7) {
     MESH_DEBUG_PRINTLN("PWRMGT: LPCOMP wake configured (AIN%d, ref=ARef)", ain_channel);
   } else if (refsel <= 6) {
@@ -222,6 +237,8 @@ void NRF52Board::configureVoltageWake(uint8_t ain_channel, uint8_t refsel) {
   }
 
   MESH_DEBUG_PRINTLN("PWRMGT: VBUS wake configured");
+
+  return true;
 }
 #endif
 
diff --git a/src/helpers/NRF52Board.h b/src/helpers/NRF52Board.h
index dba15f97..089e1dad 100644
--- a/src/helpers/NRF52Board.h
+++ b/src/helpers/NRF52Board.h
@@ -40,7 +40,7 @@ protected:
 
   bool checkBootVoltage(const PowerMgtConfig* config);
   void enterSystemOff(uint8_t reason);
-  void configureVoltageWake(uint8_t ain_channel, uint8_t refsel);
+  bool configureVoltageWake(uint8_t ain_channel, uint8_t refsel);
   virtual void initiateShutdown(uint8_t reason);
 #endif
 
diff --git a/variants/heltec_t114/T114Board.cpp b/variants/heltec_t114/T114Board.cpp
index 51db72fc..8eeb90a2 100644
--- a/variants/heltec_t114/T114Board.cpp
+++ b/variants/heltec_t114/T114Board.cpp
@@ -25,7 +25,9 @@ void T114Board::initiateShutdown(uint8_t reason) {
   digitalWrite(PIN_BAT_CTL, enable_lpcomp ? HIGH : LOW);
 
   if (enable_lpcomp) {
-    configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);
+    if (!configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel)) {
+      NVIC_SystemReset();
+    }
   }
 
   enterSystemOff(reason);
diff --git a/variants/rak4631/RAK4631Board.cpp b/variants/rak4631/RAK4631Board.cpp
index 1b5698d0..21fcbce2 100644
--- a/variants/rak4631/RAK4631Board.cpp
+++ b/variants/rak4631/RAK4631Board.cpp
@@ -31,7 +31,9 @@ void RAK4631Board::initiateShutdown(uint8_t reason) {
 
   if (reason == SHUTDOWN_REASON_LOW_VOLTAGE ||
       reason == SHUTDOWN_REASON_BOOT_PROTECT) {
-    configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);
+    if (!configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel)) {
+      NVIC_SystemReset();
+    }
   }
 
   enterSystemOff(reason);
diff --git a/variants/xiao_nrf52/XiaoNrf52Board.cpp b/variants/xiao_nrf52/XiaoNrf52Board.cpp
index 42ee6a87..85e02627 100644
--- a/variants/xiao_nrf52/XiaoNrf52Board.cpp
+++ b/variants/xiao_nrf52/XiaoNrf52Board.cpp
@@ -22,7 +22,9 @@ void XiaoNrf52Board::initiateShutdown(uint8_t reason) {
   digitalWrite(VBAT_ENABLE, enable_lpcomp ? LOW : HIGH);
 
   if (enable_lpcomp) {
-    configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);
+    if (!configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel)) {
+      NVIC_SystemReset();
+    }
   }
 
   enterSystemOff(reason);