commit c667006ca0be3ad8036dd7d6d2195d5fcc704c55
Author: Peter Cai <peter@typeblog.net>
Date:   Thu Jun 10 12:56:57 2021 +0800

    initial commit: basic control working

diff --git a/.gitignore b/.gitignore
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index 0000000..eef5389
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.vscode
+out
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diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..cde4b4a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,106 @@
+# Makefile to build an Arduino project
+# Thanks to <http://theonlineshed.com/arduino-without-the-ide-an-intro-to-unix-make>
+# Determine path of arduino core libraries
+ARDUINO_HW  := /usr/share/arduino/hardware
+# On Arch Linux, the path is /usr/share/arduino/hardware/archlinux-arduino, so
+# we use a wildcard to handle this case
+# TODO: allow overriding ARDUINO_LIB from env variables
+ARDUINO_LIB := $(firstword $(wildcard ${ARDUINO_HW}/*arduino))
+
+# Arduino core libraries
+VPATH       := \
+	${ARDUINO_LIB}/avr/cores/arduino \
+	${ARDUINO_LIB}/avr/libraries/Wire/src \
+
+VARIANTS    := ${ARDUINO_LIB}/avr/variants/standard
+# Only used for VSCode Intellisense configuration
+AVR_INC     := /usr/avr/include
+
+# Include all subdirectories from libraries we need
+VPATH       := $(foreach path, ${VPATH}, ${path} $(shell find ${path} -type d))
+
+# Add the local directory into VPATH. Potential local subdirectories also go here
+# This is to prevent the command above from including directories like .git into
+# the VPATH list
+VPATH       += ${PWD} \
+
+# Build parameters
+BUILD_DIR   := out
+CC          := avr-gcc
+CXX         := avr-g++
+OBJCOPY     := avr-objcopy
+AVRDUDE     := avrdude
+MMCU        := -mmcu=atmega328p
+INCS        := \
+	$(foreach path, ${VPATH}, -I ${path}) \
+	$(foreach path, ${VARIANTS}, -I ${path}) \
+
+CFLAGS      := -Os -DF_CPU=16000000UL ${MMCU} ${INCS}
+# Generate sections for each function and variable
+# so that LD can eliminate unused functions and variables
+CFLAGS      += -ffunction-sections -fdata-sections
+# GCC LD options to eliminate unused sections
+LDFLAGS     := ${MMCU} -Wl,--gc-sections
+
+# List all source files
+SOURCES := $(foreach path, $(VPATH), \
+	$(wildcard ${path}/*.c) $(wildcard ${path}/*.cpp) $(wildcard ${path}/*.S))
+# Remove main.cpp from the Arduino core libraries (instead of the local project)
+# This allows us to use the proper main() function instead of setup() and loop()
+SOURCES := $(filter-out ${ARDUINO_HW}%main.cpp, ${SOURCES})
+# Strip path from the file names, since they are in VPATH, which means
+# we don't need to include the full paths
+SOURCES := $(foreach file, ${SOURCES}, $(notdir ${file}))
+# Translate everything to target object files
+OBJS    := ${SOURCES}
+OBJS    := $(patsubst %.c, ${BUILD_DIR}/%.o, ${OBJS})
+OBJS    := $(patsubst %.cpp, ${BUILD_DIR}/%.o, ${OBJS})
+OBJS    := $(patsubst %.S, ${BUILD_DIR}/%_asm.o, ${OBJS})
+
+PROGRAM     := arduino-otp
+
+# Build rules for different source types
+${BUILD_DIR}/%.o: %.c
+	mkdir -p ${BUILD_DIR}
+	${CC} ${CFLAGS} -c $< -o $@ 
+ 
+${BUILD_DIR}/%.o: %.cpp
+	mkdir -p ${BUILD_DIR}
+	${CXX} ${CFLAGS} -c $< -o $@ 
+
+${BUILD_DIR}/%_asm.o: %.S
+	mkdir -p ${BUILD_DIR}
+	${CC} ${CFLAGS} -c $< -o $@ 
+
+${BUILD_DIR}/${PROGRAM}.elf: ${OBJS}
+	${CC} ${LDFLAGS} $^ -o $@
+ 
+${BUILD_DIR}/${PROGRAM}.hex: ${BUILD_DIR}/${PROGRAM}.elf
+	${OBJCOPY} -O ihex -R .eeprom $< $@
+
+define to-json-array
+	$(shell echo '$(foreach path, $1, "${path}",)' | sed "s/,$$//")
+endef
+
+# vscode intellisense configuration file
+# note that vscode will automatically format the generated file
+.vscode/c_cpp_properties.json: c_cpp_properties.json.template
+	mkdir -p .vscode
+	sed 's@__includePaths__@$(call to-json-array, ${AVR_INC} ${VPATH} ${VARIANTS})@' c_cpp_properties.json.template > .vscode/c_cpp_properties.json
+
+.PHONY: all clean upload vscode
+
+all: ${BUILD_DIR}/${PROGRAM}.hex
+
+clean:
+	rm -rf ${BUILD_DIR}
+
+upload: all
+ifndef PORT
+	$(error PORT is undefined)
+endif
+	${AVRDUDE} -F -V -c arduino -p ATMEGA328P -P ${PORT} -b 115200 -D -U flash:w:${BUILD_DIR}/${PROGRAM}.hex
+
+vscode:
+	rm -rf .vscode/c_cpp_properties.json
+	make .vscode/c_cpp_properties.json
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diff --git a/c_cpp_properties.json.template b/c_cpp_properties.json.template
new file mode 100644
index 0000000..9474bf5
--- /dev/null
+++ b/c_cpp_properties.json.template
@@ -0,0 +1,17 @@
+{
+    "configurations": [
+        {
+            "name": "AVR",
+            "includePath": [__includePaths__],
+            "intelliSenseMode": "gcc-x64",
+            "compilerPath": "/usr/bin/avr-g++",
+            "compilerArgs": [
+                "-mmcu=atmega328p"
+            ],
+            "defines": [
+                "__ATmega328P__",
+                "__AVR_ATmega328P__"
+            ]
+        }
+    ]
+}
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diff --git a/main.cpp b/main.cpp
new file mode 100644
index 0000000..da0e749
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,46 @@
+#include <Arduino.h>
+#include "motor_control.h"
+
+MotorControl motors[4] = {
+    MotorControl(5, 2),
+    MotorControl(6, 3),
+    MotorControl(7, 4),
+    MotorControl(13, 12)
+};
+
+int main() {
+    init();
+    // Enable the motor drivers
+    pinMode(8, OUTPUT);
+    digitalWrite(8, LOW);
+
+    // Initialize the controllers
+    for (int i = 0; i < 4; i++) {
+        motors[i].Init();
+    }
+
+    // Test: play A4 (440 Hz) on each successive motor every second
+    int cur_motor = -1;
+
+    while (true) {
+        unsigned long cur_micros = micros();
+
+        for (int i = 0; i < 4; i++) {
+            motors[i].Tick(cur_micros);
+        }
+
+        int new_motor = (cur_micros / 1000 / 1000) % 4;
+        
+        if (new_motor != cur_motor) {
+            motors[new_motor].TickOn(2272);
+
+            if (cur_motor != -1) {
+                motors[cur_motor].TickOff();
+            }
+
+            cur_motor = new_motor;
+        }
+    }
+
+    return 0;
+}
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diff --git a/motor_control.cpp b/motor_control.cpp
new file mode 100644
index 0000000..dd1313d
--- /dev/null
+++ b/motor_control.cpp
@@ -0,0 +1,48 @@
+#include <Arduino.h>
+#include "motor_control.h"
+
+MotorControl::MotorControl(int pin_dir, int pin_step) :
+    pin_dir(pin_dir), pin_step(pin_step),
+    last_tick_micros(0), tick_period_micros(0)
+{
+    // No actual constructor logic -- initialization is in Init()
+}
+
+void MotorControl::Init() {
+    // Initialize the pin state
+    pinMode(pin_dir, OUTPUT);
+    pinMode(pin_step, OUTPUT);
+    digitalWrite(pin_dir, LOW);
+    digitalWrite(pin_step, LOW);
+}
+
+void MotorControl::TickOn(unsigned long period_micros) {
+    tick_period_micros = period_micros;
+    // Force the next tick to happen
+    last_tick_micros = 0;
+}
+
+void MotorControl::TickOff() {
+    tick_period_micros = 0;
+}
+
+void MotorControl::Tick(unsigned long cur_micros) {
+    if (cur_micros == 0) {
+        return;
+    }
+
+    if (tick_period_micros == 0) {
+        return;
+    }
+
+    if (last_tick_micros == 0 || (cur_micros - last_tick_micros) >= tick_period_micros) {
+        DoTick();
+        last_tick_micros = cur_micros;
+    }
+}
+
+void MotorControl::DoTick() {
+    // Pulse the step pin once
+    digitalWrite(pin_step, HIGH);
+    digitalWrite(pin_step, LOW);
+}
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diff --git a/motor_control.h b/motor_control.h
new file mode 100644
index 0000000..75ae93a
--- /dev/null
+++ b/motor_control.h
@@ -0,0 +1,25 @@
+#pragma once
+
+class MotorControl {
+    private:
+        // Control pins of the stepper motor
+        int pin_dir, pin_step;
+        // Timestamp of the last motor tick
+        unsigned long last_tick_micros;
+        // Interval of motor ticking; 0 to disable the motor
+        unsigned long tick_period_micros;
+
+        void DoTick();
+    public:
+        // Constructor
+        MotorControl(int pin_dir, int pin_step);
+        // Must be called before using any other functionality (but after enabling the controllers)
+        void Init();
+        // Set the motor to tick at a given interval (inverse of frequency)
+        void TickOn(unsigned long period_micros);
+        // Turn off the motor
+        void TickOff();
+        // Perform a tick if necessary
+        // This should be called from the main event loop
+        void Tick(unsigned long cur_micros);
+};
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