arduino-pico/libraries/Wire/src/Wire.cpp

/*
    I2C Master/Slave library for the Raspberry Pi Pico RP2040

    Copyright (c) 2021 Earle F. Philhower, III <earlephilhower@yahoo.com>

    Based off of TWI/I2C library for Arduino Zero
    Copyright (c) 2015 Arduino LLC. All rights reserved.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <Arduino.h>
#include <hardware/gpio.h>
#include <hardware/i2c.h>
#include <hardware/irq.h>
#include <hardware/regs/intctrl.h>
#include "Wire.h"

#ifdef USE_TINYUSB
// For Serial when selecting TinyUSB.  Can't include in the core because Arduino IDE
// will not link in libraries called from the core.  Instead, add the header to all
// the standard libraries in the hope it will still catch some user cases where they
// use these libraries.
// See https://github.com/earlephilhower/arduino-pico/issues/167#issuecomment-848622174
#include <Adafruit_TinyUSB.h>
#endif

TwoWire::TwoWire(i2c_inst_t *i2c, pin_size_t sda, pin_size_t scl) {
    _sda = sda;
    _scl = scl;
    _i2c = i2c;
    _clkHz = TWI_CLOCK;
    _running = false;
    _txBegun = false;
    _buffLen = 0;
}

bool TwoWire::setSDA(pin_size_t pin) {
    constexpr uint32_t valid[2] = { __bitset({0, 4, 8, 12, 16, 20, 24, 28}) /* I2C0 */,
                                    __bitset({2, 6, 10, 14, 18, 22, 26})  /* I2C1 */
                                  };
    if ((!_running) && ((1 << pin) & valid[i2c_hw_index(_i2c)])) {
        _sda = pin;
        return true;
    }

    if (_running) {
        panic("FATAL: Attempting to set Wire%s.SDA while running", i2c_hw_index(_i2c) ? "1" : "");
    } else {
        panic("FATAL: Attempting to set Wire%s.SDA to illegal pin %d", i2c_hw_index(_i2c) ? "1" : "", pin);
    }
    return false;
}

bool TwoWire::setSCL(pin_size_t pin) {
    constexpr uint32_t valid[2] = { __bitset({1, 5, 9, 13, 17, 21, 25, 29}) /* I2C0 */,
                                    __bitset({3, 7, 11, 15, 19, 23, 27})  /* I2C1 */
                                  };
    if ((!_running) && ((1 << pin) & valid[i2c_hw_index(_i2c)])) {
        _scl = pin;
        return true;
    }

    if (_running) {
        panic("FATAL: Attempting to set Wire%s.SCL while running", i2c_hw_index(_i2c) ? "1" : "");
    } else {
        panic("FATAL: Attempting to set Wire%s.SCL to illegal pin %d", i2c_hw_index(_i2c) ? "1" : "", pin);
    }
    return false;
}

void TwoWire::setClock(uint32_t hz) {
    _clkHz = hz;
    if (_running) {
        i2c_set_baudrate(_i2c, hz);
    }
}

// Master mode
void TwoWire::begin() {
    if (_running) {
        // ERROR
        return;
    }
    _slave = false;
    i2c_init(_i2c, _clkHz);
    i2c_set_slave_mode(_i2c, false, 0);
    gpio_set_function(_sda, GPIO_FUNC_I2C);
    gpio_pull_up(_sda);
    gpio_set_function(_scl, GPIO_FUNC_I2C);
    gpio_pull_up(_scl);

    _running = true;
    _txBegun = false;
    _buffLen = 0;
}

static void _handler0() {
    Wire.onIRQ();
}

static void _handler1() {
    Wire1.onIRQ();
}

// Slave mode
void TwoWire::begin(uint8_t addr) {
    if (_running) {
        // ERROR
        return;
    }
    _slave = true;
    i2c_init(_i2c, _clkHz);
    i2c_set_slave_mode(_i2c, true, addr);

    // Our callback IRQ
    _i2c->hw->intr_mask = (1 << 12) | (1 << 10) | (1 << 9) | (1 << 6) | (1 << 5) | (1 << 2);

    int irqNo = I2C0_IRQ + i2c_hw_index(_i2c);
    irq_set_exclusive_handler(irqNo, i2c_hw_index(_i2c) == 0 ? _handler0 : _handler1);
    irq_set_enabled(irqNo, true);

    gpio_set_function(_sda, GPIO_FUNC_I2C);
    gpio_pull_up(_sda);
    gpio_set_function(_scl, GPIO_FUNC_I2C);
    gpio_pull_up(_scl);

    _running = true;
}

// See: https://github.com/earlephilhower/arduino-pico/issues/979#issuecomment-1328237128
#pragma GCC push_options
#pragma GCC optimize ("O0")
void TwoWire::onIRQ() {
    // Make a local copy of the IRQ status up front.  If it changes while we're
    // running the IRQ callback will fire again after returning.  Avoids potential
    // race conditions
    uint32_t irqstat = _i2c->hw->intr_stat;
    if (irqstat == 0) {
        return;
    }

    // First, pull off any data available
    if (irqstat & (1 << 2)) {
        // RX_FULL
        if (_buffLen < (int)sizeof(_buff)) {
            _buff[_buffLen++] = _i2c->hw->data_cmd & 0xff;
        } else {
            _i2c->hw->data_cmd;
        }
    }
    // RD_REQ
    if (irqstat & (1 << 5)) {
        if (_onRequestCallback) {
            _onRequestCallback();
        }
        _i2c->hw->clr_rd_req;
    }
    // TX_ABRT
    if (irqstat & (1 << 6)) {
        _i2c->hw->clr_tx_abrt;
    }
    // START_DET
    if (irqstat & (1 << 10)) {
        _slaveStartDet = true;
        _i2c->hw->clr_start_det;
    }
    // RESTART_DET
    if (irqstat & (1 << 12)) {
        if (_onReceiveCallback && _buffLen) {
            _onReceiveCallback(_buffLen);
        }
        _buffLen = 0;
        _buffOff = 0;
        _slaveStartDet = false;
        _i2c->hw->clr_restart_det;
    }
    // STOP_DET
    if (irqstat & (1 << 9)) {
        if (_onReceiveCallback && _buffLen) {
            _onReceiveCallback(_buffLen);
        }
        _buffLen = 0;
        _buffOff = 0;
        _slaveStartDet = false;
        _i2c->hw->clr_stop_det;
    }
}
#pragma GCC pop_options

void TwoWire::end() {
    if (!_running) {
        // ERROR
        return;
    }

    if (_slave) {
        int irqNo = I2C0_IRQ + i2c_hw_index(_i2c);
        irq_remove_handler(irqNo, i2c_hw_index(_i2c) == 0 ? _handler0 : _handler1);
        irq_set_enabled(irqNo, false);
    }

    i2c_deinit(_i2c);

    pinMode(_sda, INPUT);
    pinMode(_scl, INPUT);
    _running = false;
    _txBegun = false;
}

void TwoWire::beginTransmission(uint8_t addr) {
    if (!_running || _txBegun) {
        // ERROR
        return;
    }
    _addr = addr;
    _buffLen = 0;
    _buffOff = 0;
    _txBegun = true;
}

size_t TwoWire::requestFrom(uint8_t address, size_t quantity, bool stopBit) {
    if (!_running || _txBegun || !quantity || (quantity > sizeof(_buff))) {
        return 0;
    }

    _buffLen = i2c_read_blocking_until(_i2c, address, _buff, quantity, !stopBit, make_timeout_time_ms(_timeout));
    if ((_buffLen == PICO_ERROR_GENERIC) || (_buffLen == PICO_ERROR_TIMEOUT)) {
        _buffLen = 0;
    }
    _buffOff = 0;
    return _buffLen;
}

size_t TwoWire::requestFrom(uint8_t address, size_t quantity) {
    return requestFrom(address, quantity, true);
}

static bool _clockStretch(pin_size_t pin) {
    auto end = time_us_64() + 100;
    while ((time_us_64() < end) && (!digitalRead(pin))) { /* noop */ }
    return digitalRead(pin);
}

bool _probe(int addr, pin_size_t sda, pin_size_t scl, int freq) {
    int delay = (1000000 / freq) / 2;
    bool ack = false;

    pinMode(sda, INPUT_PULLUP);
    pinMode(scl, INPUT_PULLUP);
    gpio_set_function(scl, GPIO_FUNC_SIO);
    gpio_set_function(sda, GPIO_FUNC_SIO);

    digitalWrite(sda, HIGH);
    sleep_us(delay);
    digitalWrite(scl, HIGH);
    if (!_clockStretch(scl)) {
        goto stop;
    }
    digitalWrite(sda, LOW);
    sleep_us(delay);
    digitalWrite(scl, LOW);
    sleep_us(delay);
    for (int i = 0; i < 8; i++) {
        addr <<= 1;
        digitalWrite(sda, (addr & (1 << 7)) ? HIGH : LOW);
        sleep_us(delay);
        digitalWrite(scl, HIGH);
        sleep_us(delay);
        if (!_clockStretch(scl)) {
            goto stop;
        }
        digitalWrite(scl, LOW);
        sleep_us(5); // Ensure we don't change too close to clock edge
    }

    digitalWrite(sda, HIGH);
    sleep_us(delay);
    digitalWrite(scl, HIGH);
    if (!_clockStretch(scl)) {
        goto stop;
    }

    ack = digitalRead(sda) == LOW;
    sleep_us(delay);
    digitalWrite(scl, LOW);

stop:
    sleep_us(delay);
    digitalWrite(sda, LOW);
    sleep_us(delay);
    digitalWrite(scl, HIGH);
    sleep_us(delay);
    digitalWrite(sda, HIGH);
    sleep_us(delay);
    gpio_set_function(scl, GPIO_FUNC_I2C);
    gpio_set_function(sda, GPIO_FUNC_I2C);

    return ack;
}

// Errors:
//  0 : Success
//  1 : Data too long
//  2 : NACK on transmit of address
//  3 : NACK on transmit of data
//  4 : Other error
uint8_t TwoWire::endTransmission(bool stopBit) {
    if (!_running || !_txBegun) {
        return 4;
    }
    _txBegun = false;
    if (!_buffLen) {
        // Special-case 0-len writes which are used for I2C probing
        return _probe(_addr, _sda, _scl, _clkHz) ? 0 : 2;
    } else {
        auto len = _buffLen;
        auto ret = i2c_write_blocking_until(_i2c, _addr, _buff, _buffLen, !stopBit, make_timeout_time_ms(_timeout));
        _buffLen = 0;
        return (ret == len) ? 0 : 4;
    }
}

uint8_t TwoWire::endTransmission() {
    return endTransmission(true);
}

size_t TwoWire::write(uint8_t ucData) {
    if (!_running) {
        return 0;
    }

    if (_slave) {
        // Wait for a spot in the TX FIFO
        while (0 == (_i2c->hw->status & (1 << 1))) { /* noop wait */ }
        _i2c->hw->data_cmd = ucData;
        return 1;
    } else {
        if (!_txBegun || (_buffLen == sizeof(_buff))) {
            return 0;
        }
        _buff[_buffLen++] = ucData;
        return 1 ;
    }
}

size_t TwoWire::write(const uint8_t *data, size_t quantity) {
    for (size_t i = 0; i < quantity; ++i) {
        if (!write(data[i])) {
            return i;
        }
    }

    return quantity;
}

int TwoWire::available(void) {
    return _running  ? _buffLen - _buffOff : 0;
}

int TwoWire::read(void) {
    if (available()) {
        return _buff[_buffOff++];
    }
    return -1; // EOF
}

int TwoWire::peek(void) {
    if (available()) {
        return _buff[_buffOff];
    }
    return -1; // EOF
}

void TwoWire::flush(void) {
    // Do nothing, use endTransmission(..) to force
    // data transfer.
}


void TwoWire::onReceive(void(*function)(int)) {
    _onReceiveCallback = function;
}

void TwoWire::onRequest(void(*function)(void)) {
    _onRequestCallback = function;
}

#ifndef __WIRE0_DEVICE
#define __WIRE0_DEVICE i2c0
#endif
#ifndef __WIRE1_DEVICE
#define __WIRE1_DEVICE i2c1
#endif

TwoWire Wire(__WIRE0_DEVICE, PIN_WIRE0_SDA, PIN_WIRE0_SCL);
TwoWire Wire1(__WIRE1_DEVICE, PIN_WIRE1_SDA, PIN_WIRE1_SCL);