aod: lower voltage going to the display

src/drivers/St7789.cpp

@@ -27,6 +27,7 @@ void St7789::Init() {
 #endif
   NormalModeOn();
   SetVdv();
+  PowerControl();
   DisplayOn();
 }
 
@@ -176,6 +177,19 @@ void St7789::DisplayOn() {
   WriteCommand(static_cast<uint8_t>(Commands::DisplayOn));
 }
 
+void St7789::PowerControl() {
+  WriteCommand(static_cast<uint8_t>(Commands::PowerControl1));
+  constexpr uint8_t args[] = {
+    0xa4, // Constant
+    0x00, // Lowest possible voltages
+  };
+  WriteData(args, sizeof(args));
+
+  WriteCommand(static_cast<uint8_t>(Commands::PowerControl2));
+  // Lowest possible boost circuit clocks
+  WriteData(0xb3);
+}
+
 void St7789::SetAddrWindow(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1) {
   WriteCommand(static_cast<uint8_t>(Commands::ColumnAddressSet));
   uint8_t colArgs[] = {

src/drivers/St7789.h

@@ -54,6 +54,7 @@ namespace Pinetime {
       void FrameRateLow();
       void DisplayOn();
       void DisplayOff();
+      void PowerControl();
 
       void SetAddrWindow(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1);
       void SetVdv();
@@ -81,6 +82,8 @@ namespace Pinetime {
         FrameRate = 0xb3,
         VdvSet = 0xc4,
         Command2Enable = 0xdf,
+        PowerControl1 = 0xd0,
+        PowerControl2 = 0xe8,
       };
       void WriteData(uint8_t data);
       void WriteData(const uint8_t* data, size_t size);