From 0f834e0ce227812499f28be36b93b07a0414ad98 Mon Sep 17 00:00:00 2001
From: Jorj Bauer <jorj@jorj.org>
Date: Mon, 28 Dec 2020 19:28:35 -0500
Subject: [PATCH] add battery status

---
 apple/appleui.cpp |  7 +++---
 teensy/teensy.ino | 54 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/apple/appleui.cpp b/apple/appleui.cpp
index 238065b..040f2e1 100644
--- a/apple/appleui.cpp
+++ b/apple/appleui.cpp
@@ -54,9 +54,9 @@ void AppleUI::drawPercentageUIElement(uint8_t element, uint8_t percent)
 
 void AppleUI::drawBatteryStatus(uint8_t percent)
 {
-  uint16_t xoff = 301*2;
+  uint16_t xoff = 301;
   uint16_t yoff = 222;
-  
+
   // the area around the apple is 12 wide; it's exactly 11 high the
   // color is 210/202/159
 
@@ -93,7 +93,8 @@ void AppleUI::drawBatteryStatus(uint8_t percent)
       g = (float)g * alpha + (bgg * (1.0 - alpha));
       b = (float)b * alpha + (bgb * (1.0 - alpha));
 
-      g_display->drawPixel(x+xoff, y+yoff, r, g, b);
+      uint16_t color16 = ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | ((b & 0xF8) >> 3);
+      g_display->drawUIPixel(x+xoff, y+yoff, color16);
     }
   }
 }
diff --git a/teensy/teensy.ino b/teensy/teensy.ino
index 18e3ab8..9212fda 100644
--- a/teensy/teensy.ino
+++ b/teensy/teensy.ino
@@ -26,6 +26,8 @@
 
 #define RESETPIN 38
 #define DEBUGPIN 23
+#define BATTERYLEVEL 20 // analog reading of battery voltage (scaled to half)
+#define BATTERYSELECT 21 // digital select that turns on the power reading ckt
 
 #include "globals.h"
 #include "teensy-crash.h"
@@ -43,6 +45,23 @@ Bounce resetButtonDebouncer = Bounce();
 
 volatile bool cpuClockInitialized = false;
 
+// The battery voltage measurement comes through a 50% ratio voltage
+// divider; and the analog resolution is set to 8 bits (so a max of
+// 256); with a fixed voltage reference of 3.3v (standard in the
+// Teensy 4.1).  Since the voltage of a 16550 battery is 4.2v (at
+// 100%) to 2.5v (at 0%), that means we should expect the
+// currentBatteryReading to be about 97 - 163.  Since this is
+// imperfect due to tolerance in the resistors and whatnot, we might
+// as well call that 100 - 160.
+volatile uint16_t currentBatteryReading = 0;
+volatile uint16_t currentBatteryCount = 0;
+volatile uint16_t currentBatterySum = 0;
+
+#define BATTERYMIN 100
+#define BATTERYMAX 160
+// how often should we read the battery level?
+#define BATTERYPERIOD (60 * 100000)
+
 void onKeypress(int unicode)
 {
   /*
@@ -80,6 +99,9 @@ void setup()
   delay(120); // let the power settle
 
   pinMode(DEBUGPIN, OUTPUT); // for debugging
+  pinMode(BATTERYSELECT, OUTPUT);
+  digitalWrite(BATTERYSELECT, false); // leave it off by default
+  pinMode(BATTERYLEVEL, INPUT);
 
 //  enableFaultHandler();
 //  SCB_SHCSR |= SCB_SHCSR_BUSFAULTENA | SCB_SHCSR_USGFAULTENA | SCB_SHCSR_MEMFAULTENA;
@@ -344,8 +366,40 @@ void runCPU(uint32_t now)
 
 void loop()
 {
+  static uint32_t readingBattery = 0; // set to millis() + a settle time constant when we start reading
+  static uint32_t nextReadBattery = micros() + BATTERYPERIOD;
+  
   uint32_t now = micros();
 
+  if (readingBattery && now >= readingBattery) {
+    // Take 10 readings over a second and average them
+    currentBatterySum += analogRead(BATTERYLEVEL);
+    readingBattery = now + 100000; // 100 ms
+    if (++currentBatteryCount >= 10) {
+      currentBatteryReading = currentBatterySum / currentBatteryCount;
+      readingBattery = 0;
+      digitalWrite(BATTERYSELECT, false);
+      nextReadBattery = now + BATTERYPERIOD;
+
+      // Set up the displayed battery level
+      if (currentBatteryReading < BATTERYMIN)
+	currentBatteryReading = BATTERYMIN;
+      if (currentBatteryReading > BATTERYMAX)
+	currentBatteryReading = BATTERYMAX;
+	
+      ((AppleUI *)g_ui)->drawBatteryStatus(map(currentBatteryReading,
+					       BATTERYMIN, BATTERYMAX,
+					       0, 100));
+    }
+  }
+  else if (!readingBattery && now >= nextReadBattery) {
+    // start reading the battery
+    readingBattery = now + 1 * 1000000; // let it settle for 1 second
+    currentBatterySum = 0;
+    currentBatteryCount = 0;
+    digitalWrite(BATTERYSELECT, true);
+  }
+
   static bool wasBios = false; // so we can tell when it's done
   if (g_biosInterrupt) {
     runBIOS(now);