ThinkNode M1: low battery auto shutdown

examples/companion_radio/ui-new/UITask.cpp

@@ -551,7 +551,22 @@ void UITask::loop() {
   if (millis() > next_batt_chck) {
     uint16_t milliVolts = getBattMilliVolts();
     if (milliVolts > 0 && milliVolts < AUTO_SHUTDOWN_MILLIVOLTS) {
+
+      // show low battery shutdown alert
+      // we should only do this for eink displays, which will persist after power loss
+      #ifdef THINKNODE_M1
+      if (_display != NULL) {
+        _display->startFrame();
+        _display->setTextSize(2);
+        _display->setColor(DisplayDriver::RED);
+        _display->drawTextCentered(_display->width() / 2, 20, "Low Battery.");
+        _display->drawTextCentered(_display->width() / 2, 40, "Shutting Down!");
+        _display->endFrame();
+      }
+      #endif
+
       shutdown();
+
     }
     next_batt_chck = millis() + 8000;
   }

src/helpers/nrf52/ThinkNodeM1Board.h

@@ -57,6 +57,14 @@ class ThinkNodeM1Board : public mesh::MainBoard {
   }
 
   void powerOff() override {
+
+    // turn off all leds, sd_power_system_off will not do this for us
+    #ifdef P_LORA_TX_LED
+    digitalWrite(P_LORA_TX_LED, LOW);
+    #endif
+
+    // power off board
     sd_power_system_off();
+
   }
 };

variants/thinknode_m1/platformio.ini

@@ -77,6 +77,7 @@ build_flags =
   -D DISPLAY_CLASS=GxEPDDisplay
   -D OFFLINE_QUEUE_SIZE=256
   -D PIN_BUZZER=6
+  -D AUTO_SHUTDOWN_MILLIVOLTS=3300
 ;  -D MESH_PACKET_LOGGING=1
 ;  -D MESH_DEBUG=1
 build_src_filter = ${ThinkNode_M1.build_src_filter}