Copyright 2023 Travis J. West, https://traviswest.ca, Input Devices and Music Interaction Laboratory (IDMIL), Centre for Interdisciplinary Research in Music Media and Technology (CIRMMT), McGill University, Montréal, Canada, and Univ. Lille, Inria, CNRS, Centrale Lille, UMR 9189 CRIStAL, F-59000 Lille, France

SPDX-License-Identifier: LGPL-2.1-or-later

This document describes a collection of crude but effective hacks used to trick certain third party libraries into compiling despite the absence of a full blown Arduino environment on which they were originally intended to depend. Currently this is only used to enable use of the Trill-Arduino library, and as such there are large portions of the full Arduino API missing.

The Arduino ecosystem consists of boards made by a variety of manufacturers, using a variety of microcontroller hardware, and API-compatible libraries for said boards. Despite that the APIs are meant to be hardware independent, and could in principle be developed as such (e.g. using the same header files), most of "the Arduino Library" so to speak is duplicated for each independent microcontroller platform.

This Arduino hack subsystem provides such hardware independent headers. Platform-dependent implementations of these supported Arduino APIs are then found in the related platform-specific subdirectories. For platforms based on Arduino and using a compatible compiler, the upstream Arduino implementation should be preferred, although it remains as future work to integrate the Sygaldry component library with the Arduino IDE build system.

The Arduino hack is intended for platforms (such as ESP32, and Raspberry Pi Pico) where first party Arduino API support is not available, or lacks a recent enough compiler to be used with Sygaldry, to establish the bare minimum Arduino compatible API required to make use of pre-existing driver libraries for various sensors, such as Bela's Trill sensors.

Arduino.h and WProgram.h

This Arduino header is included by Trill-Arduino when the ARDUINO preprocessor symbol is undefined. A cursory and incomplete investigation suggests that Arduino.h and WProgram.h provide identical APIs, with the latter being a legacy include path.

A full Arduino.h implementation would include a number of macros and functions that are not currently supported by this hack. micros and delay are currently the only APIs that are expected to work.

// @#'Arduino.h'
#pragma once
/*
Copyright 2023 Travis J. West, https://traviswest.ca, Input Devices and Music Interaction Laboratory
(IDMIL), Centre for Interdisciplinary Research in Music Media and Technology
(CIRMMT), McGill University, Montréal, Canada, and Univ. Lille, Inria, CNRS,
Centrale Lille, UMR 9189 CRIStAL, F-59000 Lille, France
 
SPDX-License-Identifier: LGPL-2.1-or-later
*/
 
 
#include <cstdint>
 
static constexpr uint8_t HIGH = 1;
static constexpr uint8_t LOW  = 0;
static constexpr uint8_t INPUT = 0x0;
static constexpr uint8_t OUTPUT = 0x1;
static constexpr uint8_t INPUT_PULLUP = 0x2;
 
typedef bool boolean;
 
void pinMode(uint8_t pin, uint8_t mode);
void digitalWrite(uint8_t pin, uint8_t val);
//int digitalRead(uint8_t pin);
//int analogRead(uint8_t pin);
 
//unsigned long millis(void);
unsigned long micros(void);
void delay(unsigned long ms);
//void delayMicroseconds(unsigned int us);
 
// @/
 
// @#'WProgram.h'
#include "Arduino.h"
// @/

Wire.h

The TwoWire API provides access to the I2C bus.

// @#'Wire.h'
#pragma once
/*
Copyright 2023 Travis J. West, https://traviswest.ca, Input Devices and Music Interaction Laboratory
(IDMIL), Centre for Interdisciplinary Research in Music Media and Technology
(CIRMMT), McGill University, Montréal, Canada, and Univ. Lille, Inria, CNRS,
Centrale Lille, UMR 9189 CRIStAL, F-59000 Lille, France
 
SPDX-License-Identifier: LGPL-2.1-or-later
*/
 
 
#include <cstdint>
 
#define BUFFER_LENGTH 60
 
class TwoWire
{
public:
    TwoWire();
    void begin();
    void begin(int sda_pin, int scl_pin, uint32_t frequency);
    void beginTransmission(uint8_t address);
    void write(uint8_t byte);
    void write(uint8_t * buffer, uint8_t length);
    void endTransmission(bool sendStop = true);
    uint8_t requestFrom(uint8_t address, uint8_t reg);
    uint8_t available();
    uint8_t read();
};
 
extern TwoWire Wire;
 
// @/

SPI.h

The SPIClass API provides access to the SPI bus. This API is not yet implemented for any platform and should not be used.

// @#'SPI.h'
#pragma once
/*
Copyright 2010 by Cristian Maglie <c.maglie@@arduino.cc>
Copyright 2014 by Paul Stoffregen <paul@@pjrc.com> (Transaction API)
Copyright 2014 by Matthijs Kooijman <matthijs@@stdin.nl> (SPISettings AVR)
Copyright 2014 by Andrew J. Kroll <xxxajk@@gmail.com> (atomicity fixes)
Copyright 2023 Travis J. West, https://traviswest.ca, Input Devices and Music Interaction Laboratory
(IDMIL), Centre for Interdisciplinary Research in Music Media and Technology
(CIRMMT), McGill University, Montréal, Canada, and Univ. Lille, Inria, CNRS,
Centrale Lille, UMR 9189 CRIStAL, F-59000 Lille, France (port to Sygladry Arduino Hack)
 
SPI Master library for arduino.
 
SPDX-License-Identifier: LGPL-2.1-or-later
*/
 
 
#include <stdint.h>
 
static constexpr uint8_t LSBFIRST = 0;
static constexpr uint8_t MSBFIRST = 1;
 
static constexpr uint8_t SPI_MODE0 = 0;
static constexpr uint8_t SPI_MODE1 = 1;
static constexpr uint8_t SPI_MODE2 = 2;
static constexpr uint8_t SPI_MODE3 = 3;
 
class SPISettings
{
public:
    SPISettings(uint32_t clock, uint8_t bitOrder, uint8_t dataMode);
    SPISettings();
    uint32_t _clock;
    uint8_t  _bitOrder;
    uint8_t  _dataMode;
};
 
class SPIClass
{
public:
    static void begin();
 
    static void beginTransaction(SPISettings settings);
 
    static uint8_t transfer(uint8_t data);
 
    static uint16_t transfer16(uint16_t data);
 
    static void transfer(void *buf, size_t count);
 
    static void endTransaction(void);
 
    static void end();
};
 
extern SPIClass SPI;
 
// @/

Building

This document provides platform-independent header files exposed as a CMake interface library. Each platform that uses the hack should provides its own implementation of these APIs that makes use of these headers.

# @#'CMakeLists.txt'
set(lib sygsp-arduino_hack)
add_library(${lib} INTERFACE)
target_include_directories(${lib} INTERFACE .)
# @/