commit a02be354e0eb5493518c00786cc2fd5643693d06
Author: Adam Pippin <adam@label-engine.com>
Date:   Fri Apr 17 16:58:56 2020 -0700

    Initial commit

diff --git a/Colours.h b/Colours.h
new file mode 100644
index 0000000..64be257
--- /dev/null
+++ b/Colours.h
@@ -0,0 +1,19 @@
+#define TFT_BLACK         0x0000
+#define TFT_NAVY          0x000F
+#define TFT_DARKGREEN     0x03E0
+#define TFT_MAROON        0x7800
+#define TFT_PURPLE        0x780F
+#define TFT_OLIVE         0x7BE0
+#define TFT_LIGHTGREY     0xC618
+#define TFT_DARKGREY      0x7BEF
+#define TFT_BLUE          0x001F
+#define TFT_GREENYELLOW   0xB7E0
+#define TFT_GREEN         0x07E0
+#define TFT_YELLOW        0xFFE0
+#define TFT_ORANGE        0xFDA0
+#define TFT_PINK          0xFC9F
+#define TFT_CYAN          0x07FF
+#define TFT_DARKCYAN      0x03EF
+#define TFT_RED           0xF800
+#define TFT_MAGENTA       0xF81F
+#define TFT_WHITE         0xFFFF
diff --git a/Kernel.cpp b/Kernel.cpp
new file mode 100644
index 0000000..b59187c
--- /dev/null
+++ b/Kernel.cpp
@@ -0,0 +1,170 @@
+#include <M5StickC.h>
+#include "Kernel.h"
+#include "Util.h"
+#include "Colours.h"
+
+#define MAX_TASKS 8
+
+struct Task *Kernel_get_task(int pid);
+
+struct Task tasks[MAX_TASKS];
+int next_pid = 1;
+unsigned long last_tick;
+
+void Kernel_panic(char* message)
+{
+  M5.Lcd.setRotation(3);
+  M5.Lcd.fillScreen(TFT_BLUE);
+  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLUE);
+  M5.Lcd.setCursor(0, 0);
+  M5.Lcd.print("Panic! ");
+  M5.Lcd.print(message);
+  while(true) {}
+}
+
+void Kernel_setup()
+{
+  last_tick = millis();
+}
+
+void Kernel_start(int (*callback)(unsigned int), unsigned long interval)
+{
+  struct Task *process = Kernel_get_task(0);
+  if (process->pid == -1)
+  {
+    Kernel_panic("Could not start process -- reached MAX_TASKS");
+  }
+  
+  process->pid = next_pid++;
+  process->callback = callback;
+  process->run_interval = interval;
+  process->run_accumulator = interval;
+  process->signal = SIGNAL_START | SIGNAL_TICK;
+  process->running = true;
+}
+
+void Kernel_enable(int pid)
+{
+  struct Task *process = Kernel_get_task(pid);
+  if (process->pid == pid)
+  {
+    process->running = true;
+  }
+}
+
+void Kernel_disable(int pid)
+{
+  struct Task *process = Kernel_get_task(pid);
+  if (process->pid == pid)
+  {
+    process->running = false;
+  }
+}
+
+void Kernel_reap(int pid)
+{
+  struct Task *process = Kernel_get_task(pid);
+  if (process->pid != pid || process->running)
+  {
+    return;
+  }
+  process->pid = 0;
+  process->running = false;
+  process->exit_code = 0;
+  process->run_interval = 0;
+  process->run_accumulator = 0;
+  process->signal = SIGNAL_NONE;
+  process->signal_mask = 0xFFFF;
+}
+
+int Kernel_get_exit_code(int pid)
+{
+  struct Task *process = Kernel_get_task(pid);
+  int exit_code = process->pid != pid || process->running == true ? -1 : process->exit_code;
+  Kernel_reap(pid);
+  return exit_code;
+}
+
+bool Kernel_is_exited(int pid)
+{
+  struct Task *process = Kernel_get_task(pid);
+  return process->pid != pid || process->running == false;
+}
+
+struct Task *Kernel_get_task(int pid)
+{
+  for (int i=0; i<MAX_TASKS; i++)
+  {
+    if (tasks[i].pid == pid)
+    {
+      return &tasks[i];
+    }
+  }
+  struct Task empty = Task();
+  empty.pid = -1;
+  return &empty;
+}
+
+void Kernel_tick()
+{
+  unsigned long duration = millis_since(last_tick);
+  // Store the last runtime so we can calculate duration next tick. We do this at the beginning of the method
+  // so it counts the time spent running tasks as time elapsed.
+  last_tick = millis();
+
+  unsigned long next_tick_due = ULONG_MAX;
+  
+  for (int i=0; i<MAX_TASKS; i++)
+  {
+    // If the task is initialized (non-zero PID) and is marked as running
+    if (tasks[i].pid != 0 && tasks[i].running == true)
+    {
+
+      // Check if this tick's duration will push us over the run interval and if so set the TICK signal
+      if (tasks[i].run_accumulator + duration > tasks[i].run_interval)
+      {
+        // Set signal
+        tasks[i].signal |= SIGNAL_TICK;
+        // Reset accumulator so we can start counting again
+        tasks[i].run_accumulator = 0;
+      }
+      else
+      {
+        // Otherwise, accumulate time
+        tasks[i].run_accumulator += duration;
+      }
+
+      // If the process has any non-masked signals pending, run it
+      if ((tasks[i].signal & tasks[i].signal_mask) != 0)
+      {
+        // Run the task
+        int task_return = (*tasks[i].callback)(tasks[i].signal);
+        // Reset the signal
+        tasks[i].signal = SIGNAL_NONE;
+
+        // If the tasks's return value was non-zero, it has exited.
+        if (task_return != 0)
+        {
+          // Mark it as no longer running
+          tasks[i].running = false;
+          // Store the exit code
+          tasks[i].exit_code = task_return;
+        }
+      }
+      
+
+      // Check each task to see if it's the one scheduled to run on the next closest tick, and track it
+      // so we can put the processor to sleep until then.
+      if (tasks[i].run_interval - tasks[i].run_accumulator < next_tick_due)
+      {
+        next_tick_due = tasks[i].run_interval - tasks[i].run_accumulator;
+      }
+    }
+  }
+
+  // Put processor to sleep until the next scheduled run of a task
+  // Leave the home button enabled to force a wake-up before then
+  esp_sleep_enable_timer_wakeup(next_tick_due * 1000);
+  esp_sleep_enable_ext0_wakeup((gpio_num_t)37, LOW);
+  esp_light_sleep_start();
+}
diff --git a/Kernel.h b/Kernel.h
new file mode 100644
index 0000000..78cf6f7
--- /dev/null
+++ b/Kernel.h
@@ -0,0 +1,37 @@
+
+struct Task
+{
+  int pid = 0;
+  bool running = false;
+  int exit_code = 0;
+  int (*callback)(unsigned int);
+  unsigned long run_interval = 0;
+  unsigned long run_accumulator = 0;
+  unsigned int signal = 0;
+  unsigned int signal_mask = 0xFFFF;
+};
+
+void Kernel_setup();
+void Kernel_tick();
+
+// Panic and stop everything
+void Kernel_panic(char* message);
+
+// Start a new process
+void Kernel_start(int (*callback)(unsigned int), unsigned long interval);
+// Continue execution of a process
+void Kernel_enable(int pid);
+// Pause execution of a process
+void Kernel_disable(int pid);
+// Clean up exited process
+void Kernel_reap(int pid);
+
+// Check if process has exited
+bool Kernel_is_exited(int pid);
+// Get exit code of process
+int Kernel_get_exit_code(int pid);
+
+#define SIGNAL_NONE 0
+#define SIGNAL_TICK 1
+#define SIGNAL_START 2
+#define SIGNAL_STOP 4
diff --git a/PowerManagement.cpp b/PowerManagement.cpp
new file mode 100644
index 0000000..1b0ef84
--- /dev/null
+++ b/PowerManagement.cpp
@@ -0,0 +1,10 @@
+
+void PowerManagement_setup()
+{
+  
+}
+
+void PowerManagement_tick()
+{
+
+}
diff --git a/PowerManagement.h b/PowerManagement.h
new file mode 100644
index 0000000..da44c18
--- /dev/null
+++ b/PowerManagement.h
@@ -0,0 +1,3 @@
+
+void PowerManagement_setup();
+void PowerManagement_tick();
diff --git a/Util.cpp b/Util.cpp
new file mode 100644
index 0000000..41356ba
--- /dev/null
+++ b/Util.cpp
@@ -0,0 +1,16 @@
+#include <M5StickC.h>
+#include "Util.h"
+
+unsigned long millis_since(unsigned long timestamp)
+{
+  unsigned long now = millis();
+
+  if (now < timestamp)
+  {
+    return (4294967295 - timestamp) + millis();
+  }
+  else
+  {
+    return millis() - timestamp;
+  }
+}
diff --git a/Util.h b/Util.h
new file mode 100644
index 0000000..77ceed9
--- /dev/null
+++ b/Util.h
@@ -0,0 +1,2 @@
+
+unsigned long millis_since(unsigned long timestamp);
diff --git a/watchos.ino b/watchos.ino
new file mode 100644
index 0000000..22a4d10
--- /dev/null
+++ b/watchos.ino
@@ -0,0 +1,44 @@
+#include <M5StickC.h>
+#include "PowerManagement.h"
+#include "Kernel.h"
+#include "Colours.h"
+
+int count = 0;
+int test_func(unsigned int signal)
+{
+  M5.Lcd.fillScreen(TFT_DARKGREY);
+  M5.Lcd.setCursor(0, 0);
+  if (signal & SIGNAL_START)
+  {
+    M5.Lcd.setRotation(3);
+    M5.Lcd.print("Initializing...");
+  }
+  if (signal & SIGNAL_STOP)
+  {
+    M5.Lcd.print("Stopping");
+    return 255;
+  }
+  if (signal & SIGNAL_TICK)
+  {
+    count++;
+    M5.Lcd.print("Ran: ");
+    M5.Lcd.print(String(count));
+    M5.Lcd.print(" times");
+  }
+  return 0;
+}
+
+void setup()
+{
+  M5.begin();
+  Kernel_setup();
+  PowerManagement_setup();
+
+  Kernel_start(&test_func, 1000);
+}
+
+void loop()
+{
+  Kernel_tick();
+  PowerManagement_tick();
+}