ThinkNode M6: button shutdown/wake for repeater and room server

Fixes #2313. Hold the Function Button ~5s to power off (matches the
board's stock firmware timing); any press wakes it back up, since the
chip is fully halted in SYSTEMOFF and can't measure hold duration
while off. The power LED blinks 3x on both shutdown and wake/boot to
confirm the action registered.

ThinkNodeM6Board::powerOff() now arms the button as a GPIO wake source
(pull-up + SENSE_LOW) before entering SYSTEMOFF via NRF52Board::powerOff().

Scoped to simple_repeater and simple_room_server only, since
companion_radio already has an in-flight change (#2837) moving its
button handling into UITask.

Tested on hardware: shutdown, wake, and LED feedback all verified on
a physical ThinkNode M6 repeater.

examples/simple_repeater/main.cpp

@@ -30,10 +30,14 @@ static char ethernet_command[160];
 // For power saving
 unsigned long POWERSAVING_FIRSTSLEEP_SECS = 120; // The first sleep (if enabled) from boot
 
-#if defined(PIN_USER_BTN) && defined(_SEEED_SENSECAP_SOLAR_H_)
+#if defined(PIN_USER_BTN) && (defined(_SEEED_SENSECAP_SOLAR_H_) || defined(THINKNODE_M6))
 static unsigned long userBtnDownAt = 0;
+#if defined(THINKNODE_M6)
+#define USER_BTN_HOLD_OFF_MILLIS 5000   // matches Elecrow's stock firmware UX
+#else
 #define USER_BTN_HOLD_OFF_MILLIS 1500
 #endif
+#endif
 
 void setup() {
   Serial.begin(115200);
@@ -170,13 +174,22 @@ void loop() {
   }
 #endif
 
-#if defined(PIN_USER_BTN) && defined(_SEEED_SENSECAP_SOLAR_H_) && !defined(DISPLAY_CLASS)
-  // Hold the user button to power off the SenseCAP Solar repeater.
+#if defined(PIN_USER_BTN) && (defined(_SEEED_SENSECAP_SOLAR_H_) || defined(THINKNODE_M6)) && !defined(DISPLAY_CLASS)
+  // Hold the user button to power off the repeater.
   int btnState = digitalRead(PIN_USER_BTN);
   if (btnState == LOW) {
     if (userBtnDownAt == 0) {
       userBtnDownAt = millis();
     } else if ((unsigned long)(millis() - userBtnDownAt) >= USER_BTN_HOLD_OFF_MILLIS) {
+#if defined(THINKNODE_M6) && defined(PIN_LED_RED)
+      // blink the power LED a few times to confirm the hold was registered
+      for (int i = 0; i < 3; i++) {
+        digitalWrite(PIN_LED_RED, HIGH);
+        delay(150);
+        digitalWrite(PIN_LED_RED, LOW);
+        delay(150);
+      }
+#endif
       Serial.println("Powering off...");
       board.powerOff();  // does not return
     }

examples/simple_room_server/main.cpp

@@ -26,6 +26,11 @@ static char command[MAX_POST_TEXT_LEN+1];
 static char ethernet_command[MAX_POST_TEXT_LEN+1];
 #endif
 
+#if defined(PIN_USER_BTN) && defined(THINKNODE_M6)
+static unsigned long userBtnDownAt = 0;
+#define USER_BTN_HOLD_OFF_MILLIS 5000   // matches Elecrow's stock firmware UX
+#endif
+
 void setup() {
   Serial.begin(115200);
   delay(1000);
@@ -148,6 +153,30 @@ void loop() {
   }
 #endif
 
+#if defined(PIN_USER_BTN) && defined(THINKNODE_M6) && !defined(DISPLAY_CLASS)
+  // Hold the user button to power off the room server.
+  int btnState = digitalRead(PIN_USER_BTN);
+  if (btnState == LOW) {
+    if (userBtnDownAt == 0) {
+      userBtnDownAt = millis();
+    } else if ((unsigned long)(millis() - userBtnDownAt) >= USER_BTN_HOLD_OFF_MILLIS) {
+#ifdef PIN_LED_RED
+      // blink the power LED a few times to confirm the hold was registered
+      for (int i = 0; i < 3; i++) {
+        digitalWrite(PIN_LED_RED, HIGH);
+        delay(150);
+        digitalWrite(PIN_LED_RED, LOW);
+        delay(150);
+      }
+#endif
+      Serial.println("Powering off...");
+      board.powerOff();  // does not return
+    }
+  } else {
+    userBtnDownAt = 0;
+  }
+#endif
+
   the_mesh.loop();
   sensors.loop();
 #ifdef DISPLAY_CLASS

variants/thinknode_m6/ThinkNodeM6Board.cpp

@@ -15,6 +15,20 @@ void ThinkNodeM6Board::begin() {
   digitalWrite(P_LORA_TX_LED, LOW);
 #endif
 
+#ifdef PIN_USER_BTN
+  pinMode(PIN_USER_BTN, INPUT_PULLUP);
+#endif
+
+#ifdef PIN_LED_RED
+  // blink the power LED a few times to confirm power-on/wake
+  for (int i = 0; i < 3; i++) {
+    digitalWrite(PIN_LED_RED, HIGH);
+    delay(150);
+    digitalWrite(PIN_LED_RED, LOW);
+    delay(150);
+  }
+#endif
+
   delay(10); // give sx1262 some time to power up
 }
 

variants/thinknode_m6/ThinkNodeM6Board.h

@@ -43,6 +43,12 @@ public:
     digitalWrite(P_LORA_TX_LED, LOW);
     #endif
 
+    #ifdef PIN_USER_BTN
+    while (digitalRead(PIN_USER_BTN) == LOW);  // wait for release, avoid instant re-trigger
+    // keep pull-up enabled in system-off so the wake line doesn't float low
+    nrf_gpio_cfg_sense_input(digitalPinToInterrupt(g_ADigitalPinMap[PIN_USER_BTN]), NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_SENSE_LOW);
+    #endif
+
     // power off board
     NRF52Board::powerOff();
   }