aod: PPI/RTC-based backlight brightness

1 files changed, 23 insertions, 1 deletions

diff --git a/src/components/brightness/BrightnessController.h b/src/components/brightness/BrightnessController.h
index 7f86759a..650749a8 100644
--- a/src/components/brightness/BrightnessController.h
+++ b/src/components/brightness/BrightnessController.h
@@ -2,11 +2,14 @@
 
 #include <cstdint>
 
+#include "nrf_ppi.h"
+#include "nrfx_gpiote.h"
+
 namespace Pinetime {
   namespace Controllers {
     class BrightnessController {
     public:
-      enum class Levels { Off, Low, Medium, High };
+      enum class Levels { Off, AlwaysOn, Low, Medium, High };
       void Init();
 
       void Set(Levels level);
@@ -20,6 +23,25 @@ namespace Pinetime {
 
     private:
       Levels level = Levels::High;
+      static constexpr uint8_t UNSET = UINT8_MAX;
+      uint8_t lastPin = UNSET;
+      // Maximum time (μs) it takes for the RTC to fully stop
+      static constexpr uint8_t rtcStopTime = 46;
+      // Frequency of timer used for PWM (Hz)
+      static constexpr uint16_t timerFrequency = 32768;
+      // Backlight PWM frequency (Hz)
+      static constexpr uint16_t pwmFreq = 1000;
+      // Wraparound point in timer ticks
+      // Defines the number of brightness levels between each pin
+      static constexpr uint16_t timerPeriod = timerFrequency / pwmFreq;
+      // Warning: nimble reserves some PPIs
+      // https://github.com/InfiniTimeOrg/InfiniTime/blob/034d83fe6baf1ab3875a34f8cee387e24410a824/src/libs/mynewt-nimble/nimble/drivers/nrf52/src/ble_phy.c#L53
+      // SpiMaster uses PPI 0 for an erratum workaround
+      // Channel 1, 2 should be free to use
+      static constexpr nrf_ppi_channel_t ppiBacklightOn = NRF_PPI_CHANNEL1;
+      static constexpr nrf_ppi_channel_t ppiBacklightOff = NRF_PPI_CHANNEL2;
+
+      void ApplyBrightness(uint16_t val);
     };
   }
 }