From 4f767e412687d3400eeebabee74691ec31a997b8 Mon Sep 17 00:00:00 2001
From: Ethan-chen1234-zy <ethan.chen@rakwireless.com>
Date: Sat, 14 Mar 2026 16:42:50 +0800
Subject: [PATCH] nRF52: Move low-VDD System OFF logic to variant hook

---
 src/platform/nrf52/main-nrf52.cpp            | 23 ++++---------------
 variants/nrf52840/rak_wismeshtag/variant.cpp | 24 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/src/platform/nrf52/main-nrf52.cpp b/src/platform/nrf52/main-nrf52.cpp
index af65446b4..9b26721c0 100644
--- a/src/platform/nrf52/main-nrf52.cpp
+++ b/src/platform/nrf52/main-nrf52.cpp
@@ -45,13 +45,16 @@
 #endif
 
 uint16_t getVDDVoltage();
-void cpuDeepSleep(uint32_t msecToWake);
 
 // Weak empty variant shutdown prep function.
 // May be redefined by variant files.
 void variant_shutdown() __attribute__((weak));
 void variant_shutdown() {}
 
+// Optional variant hook called each nrf52Loop(); e.g. for low-VDD System OFF.
+void variant_nrf52LoopHook(void) __attribute__((weak));
+void variant_nrf52LoopHook(void) {}
+
 static nrfx_wdt_t nrfx_wdt = NRFX_WDT_INSTANCE(0);
 static nrfx_wdt_channel_id nrfx_wdt_channel_id_nrf52_main;
 
@@ -328,23 +331,7 @@ void nrf52Loop()
     checkSDEvents();
     reportLittleFSCorruptionOnce();
 
-#ifdef LOW_VDD_SYSTEMOFF_DELAY_MS   // rak_wismeshtag does not have a USB VBUS connected
-    // If VDD stays unsafe for a while (typically during brownout),
-    // force System OFF to avoid flash writes / SoftDevice instability loops.
-    // Skip when VBUS is present to allow recovery while USB-powered.
-    if (!powerHAL_isVBUSConnected()) {
-        static uint32_t low_vdd_since_ms = 0;
-        if (!powerHAL_isPowerLevelSafe()) {
-            if (low_vdd_since_ms == 0)
-                low_vdd_since_ms = millis();
-            if ((uint32_t)(millis() - low_vdd_since_ms) >= (uint32_t)LOW_VDD_SYSTEMOFF_DELAY_MS) {
-                cpuDeepSleep(portMAX_DELAY);
-            }
-        } else {
-            low_vdd_since_ms = 0;
-        }
-    }
-#endif
+    variant_nrf52LoopHook();  // Optional variant hook called each nrf52Loop();
 }
 
 #ifdef USE_SEMIHOSTING
diff --git a/variants/nrf52840/rak_wismeshtag/variant.cpp b/variants/nrf52840/rak_wismeshtag/variant.cpp
index a035fbaf0..c2a899ed5 100644
--- a/variants/nrf52840/rak_wismeshtag/variant.cpp
+++ b/variants/nrf52840/rak_wismeshtag/variant.cpp
@@ -22,6 +22,10 @@
 #include "nrf.h"
 #include "wiring_constants.h"
 #include "wiring_digital.h"
+#include "power/PowerHAL.h"
+#include "sleep.h"
+#include "FreeRTOS.h"
+#include "Arduino.h"
 
 const uint32_t g_ADigitalPinMap[] = {
     // P0
@@ -40,3 +44,23 @@ void initVariant()
     pinMode(PIN_3V3_EN, OUTPUT);
     digitalWrite(PIN_3V3_EN, HIGH);
 }
+
+#ifdef LOW_VDD_SYSTEMOFF_DELAY_MS
+void variant_nrf52LoopHook(void)
+{
+    // If VDD stays unsafe for a while (brownout), force System OFF.
+    // Skip when VBUS present to allow recovery while USB-powered.
+    if (!powerHAL_isVBUSConnected()) {
+        static uint32_t low_vdd_since_ms = 0;
+        if (!powerHAL_isPowerLevelSafe()) {
+            if (low_vdd_since_ms == 0)
+                low_vdd_since_ms = millis();
+            if ((uint32_t)(millis() - low_vdd_since_ms) >= (uint32_t)LOW_VDD_SYSTEMOFF_DELAY_MS) {
+                cpuDeepSleep(portMAX_DELAY);
+            }
+        } else {
+            low_vdd_since_ms = 0;
+        }
+    }
+}
+#endif