Use power down mode to save power

.clang-format

@@ -0,0 +1,22 @@
+# http://releases.llvm.org/6.0.0/tools/clang/docs/ClangFormatStyleOptions.html
+BasedOnStyle: Google
+AccessModifierOffset: -4
+AllowShortBlocksOnASingleLine: false
+AllowShortFunctionsOnASingleLine: None
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+BreakBeforeBraces: Allman
+BraceWrapping:
+  AfterNamespace: false
+BreakBeforeTernaryOperators: false
+ColumnLimit: 100
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 4
+IndentWidth: 4
+Standard: Cpp11
+TabWidth: 4
+UseTab: ForIndentation
+DerivePointerAlignment: false
+PointerAlignment: Left
+NamespaceIndentation: None
+IndentCaseLabels: true

Build.sh

@@ -21,6 +21,9 @@ $CAKELISP --verbose-processes --skip-build \
 # Arduino build expects things to have specific names and extensions
 mv cakelisp_cache/DrinkCounter/DrinkCounter.cake.c cakelisp_cache/DrinkCounter/DrinkCounter.ino || exit $?
 
+cp src/LowPower.* cakelisp_cache/DrinkCounter/ || exit $?
+mv cakelisp_cache/DrinkCounter/LowPower.c cakelisp_cache/DrinkCounter/LowPower.ino || exit $?
+
 /media/macoy/Preserve/Programs/arduino-cli_0.29.0-rc.1_Linux_64bit/arduino-cli --no-color \
 	compile -b arduino:avr:uno ./cakelisp_cache/DrinkCounter/DrinkCounter.ino || exit $?
 

ReadMe.org

@@ -6,3 +6,9 @@ Currently an Arduino project for helping me count my drinks.
 
 - Download the [[https://github.com/arduino/arduino-cli/releases][Arduino CLI]]. There may be more steps because I had installed the IDE first before I found the CLI.
 - Update ~Build.sh~ to point to the Arduino CLI install.
+
+* Notes
+- [[https://arduino.github.io/arduino-cli/0.29/sketch-build-process/][Arduino build process]]
+- [[https://arduino.github.io/arduino-cli/0.29/platform-specification/][Arduino platform specification]]
+- [[https://blog.duk.io/sleeping-atmega328-on-1ua-with-timer-wakeup/][Low power sleep with timer]]
+- [[https://www.tutorialspoint.com/deep-sleep-in-arduino][Deep sleep in Arduino]]

src/DrinkCounter.cake

@@ -9,14 +9,21 @@
 
 (import "CHelpers.cake")
 
+(c-import "LowPower.h")
+
+(defstruct-local drink-settings
+  max-drinks-per-week char
+  max-drinks-in-one-day char)
+
 (defun setup ()
   (pinMode LED_BUILTIN OUTPUT))
 
 (defun loop ()
   ;; turn the LED on (HIGH is the voltage level)
   (digitalWrite LED_BUILTIN HIGH)
-  ;; wait for a second
-  (delay 10000)
+  ;; wait for a bit in low power mode
+  ;; TODO: Use an external clock instead of watchdog to save power
+  (startLowPowerSleep SLEEP_8S)
   ;; turn the LED off by making the voltage LOW
   (digitalWrite LED_BUILTIN LOW)
   ;; wait for a second

src/LowPower.c

@@ -0,0 +1,58 @@
+// Partially copied from https://github.com/rocketscream/Low-Power
+#include "LowPower.h"
+
+#include <avr/interrupt.h>
+#include <avr/power.h>
+#include <avr/sleep.h>
+#include <avr/wdt.h>
+
+// Only Pico Power devices can change BOD settings through software
+#define sleep_bod_disable()                                                                  \
+	do                                                                                       \
+	{                                                                                        \
+		unsigned char tempreg;                                                               \
+		__asm__ __volatile__(                                                                \
+		    "in %[tempreg], %[mcucr]"                                                        \
+		    "\n\t"                                                                           \
+		    "ori %[tempreg], %[bods_bodse]"                                                  \
+		    "\n\t"                                                                           \
+		    "out %[mcucr], %[tempreg]"                                                       \
+		    "\n\t"                                                                           \
+		    "andi %[tempreg], %[not_bodse]"                                                  \
+		    "\n\t"                                                                           \
+		    "out %[mcucr], %[tempreg]"                                                       \
+		    : [ tempreg ] "=&d"(tempreg)                                                     \
+		    : [ mcucr ] "I" _SFR_IO_ADDR(MCUCR), [ bods_bodse ] "i"(_BV(BODS) | _BV(BODSE)), \
+		      [ not_bodse ] "i"(~_BV(BODSE)));                                               \
+	} while (0)
+
+// Only Pico Power devices can change BOD settings through software
+#define lowPowerBodOff(mode)  \
+	do                        \
+	{                         \
+		set_sleep_mode(mode); \
+		cli();                \
+		sleep_enable();       \
+		sleep_bod_disable();  \
+		sei();                \
+		sleep_cpu();          \
+		sleep_disable();      \
+		sei();                \
+	} while (0);
+
+ISR(WDT_vect)
+{
+	// WDIE & WDIF is cleared in hardware upon entering this ISR
+	wdt_disable();
+}
+
+// the loop function runs over and over again forever
+void startLowPowerSleep(period_t period)
+{
+	// These are disabled from here on out!
+	ADCSRA &= ~(1 << ADEN);
+	wdt_enable(period);
+	WDTCSR |= (1 << WDIE);
+	lowPowerBodOff(SLEEP_MODE_PWR_DOWN);
+	// end low sleep here
+}

src/LowPower.h

@@ -0,0 +1,17 @@
+#ifndef LOWPOWER_H
+#define LOWPOWER_H
+typedef enum period_t {
+  SLEEP_15MS,
+  SLEEP_30MS,
+  SLEEP_60MS,
+  SLEEP_120MS,
+  SLEEP_250MS,
+  SLEEP_500MS,
+  SLEEP_1S,
+  SLEEP_2S,
+  SLEEP_4S,
+  SLEEP_8S,
+  SLEEP_FOREVER
+} period_t;
+void startLowPowerSleep(period_t period);
+#endif