Sasapea's Lab

公開済みのRP1-GPIOライブラリを利用したソフトウェアI2Cライブラリを作ってみた。

簡単そうと思って始めたもののGPIOが非同期実行なためにマイクロ秒レベルで時間制御するのがやっかいすぎておおハマリ。(-_-;)

それと1MHz程度まで行けると予想していたのにGPIO入力のウェイトが大きすぎて350KHz程度の速度しかでない．．．とか、想定外のことがありすぎだったがなんとか完成。

【仕様】
・マスターモードのみ
・100KHz/400KHzのみ
・7bitアドレスのみ
・リピーテッド・スタート対応
・クロック・ストレッチ対応
・マルチ・マスター対応
・ArduinoのWire準拠クラス対応

【I2Cデバイスを列挙するサンプル・プログラム】

#include <stdio.h>
#include "rp1-gpio.h"
#include "i2c-gpio.h"

RP1_GPIO rp1;
I2C_GPIO i2c(rp1, 3, 2);

int main(int argc, char **argv)
{
  rp1.begin();
  i2c.begin();
  int cnt = 0;
  for (int i = 1; i < 0x7F; ++i)
  {
    if (i2c.write(i, nullptr, 0) == 0)
    {
      printf("%02X ", i);
      ++cnt;
    }
  }
  printf("\n%d devices.\n", cnt);
  rp1.end();
  return 0;
}

#include <stdio.h>

#include "rp1-gpio.h"

#include "i2c-gpio.h"

RP1_GPIO rp1;

I2C_GPIO i2c(rp1, 3, 2);

int main(int argc, char **argv)

{

rp1.begin();

i2c.begin();

int cnt = 0;

for (int i = 1; i < 0x7F; ++i)

{

if (i2c.write(i, nullptr, 0) == 0)

{

printf("%02X ", i);

++cnt;

}

printf("\n%d devices.\n", cnt);

rp1.end();

return 0;

}

【I2Cデバイスを列挙するサンプル・プログラム(Arduinoふう)】

#include <stdio.h>
#include "rp1-gpio.h"
#include "i2c-gpio.h"

RP1_GPIO rp1;
TwoWire Wire(rp1, 3, 2);

int main(int argc, char **argv)
{
  rp1.begin();
  Wire.begin();
  int cnt = 0;
  for (int i = 1; i < 0x7F; ++i)
  {
    Wire.beginTransmission(i);
    if (Wire.endTransmission() == 0)
    {
      printf("%02X ", i);
      ++cnt;
    }
  }
  printf("\n%d devices.\n", cnt);
  rp1.end();
  return 0;
}

#include <stdio.h>

#include "rp1-gpio.h"

#include "i2c-gpio.h"

RP1_GPIO rp1;

TwoWire Wire(rp1, 3, 2);

int main(int argc, char **argv)

{

rp1.begin();

Wire.begin();

int cnt = 0;

for (int i = 1; i < 0x7F; ++i)

{

Wire.beginTransmission(i);

if (Wire.endTransmission() == 0)

{

printf("%02X ", i);

++cnt;

}

printf("\n%d devices.\n", cnt);

rp1.end();

return 0;

}

【修正】
2025-05-13
ソースをより読みやすくしたのとコンフリクト・チェックのタイミングを変更。

2025-05-12
TwoWire::setClock()が間違ってたので修正。

2025-05-10
start/stop condition処理のエラーチェックを強化。

2025-05-06
rp1-gpio.hのpinMode()修正にともなう初期化処理の変更。

【ライブラリ】

/*
  i2c-gpio.h - Software I2C Driver for RP1-GPIO

  Copyright (c) 2025 Sasapea's Lab. All right reserved.

  This program is free software: you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation, either version 3 of
  the License, or at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#pragma once

#include "rp1-gpio.h"

class I2C_GPIO
{
  public:

    typedef enum
    {
      MODE_100KHz,
      MODE_400KHz,
    } MODE;

    typedef enum
    {
      STATUS_OK        = 0,
      STATUS_NAK       = -1,
      STATUS_BUSY      = -2,
      STATUS_TIMEOUT   = -3,
    } STATUS;

    I2C_GPIO(RP1_GPIO &gpio, int scl, int sda)
      : _gpio(&gpio), _scl(scl), _sda(sda), _spec(SPECS)
    {
    }

    virtual ~I2C_GPIO(void)
    {
    }

    void begin(MODE mode = MODE_100KHz)
    {
      _spec = &SPECS[mode];
      initIO();
    }

    int write(int addr, const void *buf, size_t len, bool sendStop = true)
    {
      STATUS rv = STATUS_NAK;
      size_t cnt = 0;
      if ((addr & ~0x7F) == 0)
      {
        if ((rv = start()) == STATUS_OK)
        {
          if ((rv = write((addr << 1) | 0)) == STATUS_OK)
          {
            const uint8_t *p = (const uint8_t *)buf;
            for (; cnt < len; ++cnt)
            {
              if ((rv = write(*p++)) != STATUS_OK)
                break;
            }
          }
          rv = stop(sendStop, rv);
        }
      }
      return rv ? rv : cnt;
    }

    int read(int addr, void *buf, size_t len, bool sendStop = true)
    {
      STATUS rv = STATUS_NAK;
      size_t cnt = 0;
      if ((addr & ~0x7F) == 0)
      {
        if ((rv = start()) == STATUS_OK)
        {
          if ((rv = write((addr << 1) | 1)) == STATUS_OK)
          {
            uint8_t b, *p = (uint8_t *)buf;
            for (; cnt < len; ++cnt)
            {
              if ((rv = read(b, cnt + 1 < len)) != STATUS_OK)
                break;
              *p++ = b;
            }
          }
          rv = stop(sendStop, rv);
        }
      }
      return rv ? rv : cnt;
    }

    int writeAndRead(int addr, const void *wbuf, size_t wlen, void *rbuf, size_t rlen)
    {
      int rv = 0;
      if (wbuf && wlen)
      {
        if (write(addr, wbuf, wlen, rbuf && rlen ? false : true) < 0)
          return 0;
      }
      if (rbuf && rlen)
        rv = read(addr, rbuf, rlen);
      return rv;
    }

  private:

    typedef struct {
      uint16_t THDSTA, THDDAT, TLOW, THIGH, TSUSTA, TSUSTO, TSUDAT, TBUF;
    } spec_t;

    static constexpr spec_t SPECS[3] = {
      { 4000, 300, 4700, 4000, 4700, 4000, 250, 4700 }, /* Standard Mode (100KHz) */
      {  600,   0, 1300,  600,  600,  600, 100, 1300 }, /* Fast Mode     (400KHz) */
    };

    static constexpr int  LOW  = 0;
    static constexpr int  HIGH = 1;

    static constexpr long DELAY_AD   = 300L;       /* 300ns */
    static constexpr long TIMEOUT_CS = 200000000L; /* 200ms */

    RP1_GPIO *_gpio;
    int       _scl;
    int       _sda;
    const spec_t *_spec;

    inline void initIO(void)
    {
      /* Keep signal lines glitch-free */
      _gpio->setPullUpDown(_sda, _gpio->PULL_UP);
      _gpio->setPullUpDown(_scl, _gpio->PULL_UP);
      _gpio->pinMode(_sda, _gpio->OPEN_DRAIN, _gpio->HIGH);
      _gpio->pinMode(_scl, _gpio->OPEN_DRAIN, _gpio->HIGH);
    }

    inline int input(int pin)
    {
      return _gpio->digitalRead(pin) ? HIGH : LOW;
    }

    inline void output(int pin, int data)
    {
      _gpio->digitalWrite(pin, data ? _gpio->HIGH : _gpio->LOW);
    }

    inline void data(int data)
    {
      output(_sda, data ? _gpio->HIGH : _gpio->LOW);
    }

    STATUS clock(int data, bool check = false)
    {
      output(_scl, data);
      /* rising edge ? */
      if (data)
      {
        /* clock stretching */
        for (unsigned long t = _gpio->nanos(); input(_scl) == LOW; )
        {
          if (_gpio->nanos() - t >= TIMEOUT_CS)
            return STATUS_TIMEOUT;
        }
        /* check bus conflicts */
        if (check && (input(_sda) == LOW))
          return STATUS_BUSY;
      }
      return STATUS_OK;
    }

    inline void delay(long ns)
    {
      if ((ns -= DELAY_AD) > 0)
        _gpio->delayNanoseconds(ns);
    }

    STATUS start(void)
    {
      if ((input(_sda) == LOW) || (input(_scl) == LOW))
      {
        delay(_spec->TBUF);
        return STATUS_BUSY;
      }
      data(LOW);
      delay(_spec->THDSTA);
      if (input(_scl) == LOW)
      {
        data(HIGH);
        delay(_spec->TBUF);
        return STATUS_BUSY;
      }
      clock(LOW);
      delay(_spec->THDDAT);
      return STATUS_OK;
    }

    STATUS stop(bool stop, STATUS status)
    {
      STATUS rv1, rv2;
      if (status < STATUS_NAK)
      {
        data(HIGH);
        clock(HIGH);
        delay(_spec->TBUF);
      }
      else if (stop || (status != STATUS_OK))
      {
        data(LOW);
        delay(_spec->TLOW);
        rv1 = clock(HIGH);
        delay(_spec->TSUSTO);
        data(HIGH);
        rv2 = input(_sda) == LOW ? STATUS_BUSY : STATUS_OK;
        delay(_spec->TBUF);
      }
      else
      {
        data(HIGH);
        delay(_spec->TSUSTA);
        rv1 = rv2 = clock(HIGH, true);
        delay(_spec->TSUSTO);
      }
      return status ? status : (rv1 ? rv1 : rv2);
    }

    STATUS write(uint8_t b)
    {
      STATUS rv;
      for (uint8_t i = 0x80; i; i >>= 1)
      {
        data(b & i);
        delay(_spec->TLOW);
        if ((rv = clock(HIGH, b & i)) != STATUS_OK)
          return rv;
        delay(_spec->THIGH);
        clock(LOW);
        delay(_spec->THDDAT);
      }
      data(HIGH);
      delay(_spec->TLOW);
      if ((rv = clock(HIGH)) != STATUS_OK)
        return rv;
      delay(_spec->THIGH);
      if (input(_sda))
        rv = STATUS_NAK;
      clock(LOW);
      delay(_spec->THDDAT);
      return rv;
    }

    STATUS read(uint8_t &b, bool ack = true)
    {
      STATUS rv;
      b = 0;
      data(HIGH);
      for (uint8_t i = 0x80; i; i >>= 1)
      {
        delay(_spec->TLOW);
        if ((rv = clock(HIGH)) != STATUS_OK)
          return rv;
        delay(_spec->THIGH);
        b |= input(_sda) ? i : 0;
        clock(LOW);
        delay(_spec->THDDAT);
      }
      if (ack)
        data(LOW);
      delay(_spec->TLOW);
      if ((rv = clock(HIGH)) != STATUS_OK)
        return rv;
      delay(_spec->THIGH);
      clock(LOW);
      delay(_spec->THDDAT);
      return rv;
    }
};

class TwoWire : public I2C_GPIO
{
  public:

    TwoWire(RP1_GPIO &gpio, int scl, int sda) : I2C_GPIO(gpio, scl, sda)
    {
    }

    virtual ~TwoWire(void)
    {
    }

    void setClock(long speed)
    {
      _speed = (speed <= 100000 ? MODE_100KHz : MODE_400KHz);
      begin();
    }

    void begin(void)
    {
      I2C_GPIO::begin(_speed);
    }

    void end(void)
    {
    }

    void beginTransmission(int address)
    {
      _addr  = address;
      _count = 0;
      _index = 0;
      _error = 0;
    }

    int endTransmission(bool sendStop = true)
    {
      if (_error)
        return 1; // buffer overflow
      int rv = I2C_GPIO::write(_addr, _buffer, _index, sendStop);
      if (rv == (int)_index)
        return 0; // success
      return (rv < 0 ? 2 : 3);
    }

    int requestFrom(int address, size_t quantity, bool sendStop = true)
    {
      if (quantity > sizeof(_buffer))
        quantity = sizeof(_buffer);
      int read = I2C_GPIO::read(address, _buffer, quantity, sendStop);
      _count = read > 0 ? read : 0;
      _index = 0;
      return _count;
    }

    virtual size_t write(uint8_t data)
    {
      if (_index >= sizeof(_buffer))
      {
        _error = 1;
        return 0;
      }
      _buffer[_index++] = data;
      return 1;
    }

    virtual size_t write(const void *buf, size_t len)
    {
      uint8_t cnt = 0;
      const uint8_t *p = (const uint8_t *)buf;
      while (len--)
        cnt += write(*p++);
      return cnt;
    }

    virtual size_t available(void)
    {
      return (_index < _count ? _count - _index : 0);
    }

    virtual int read(void)
    {
      int value = -1;
      if(_index < _count)
        value = _buffer[_index++];
      return value;
    }

    virtual size_t readBytes(void *buf, size_t len)
    {
      uint8_t *p = (uint8_t *)buf;
      size_t cnt;
      for (cnt = 0; cnt < len; ++cnt)
      {
        int c = read();
        if (c < 0)
          break;
        *p++ = c;
      }
      return cnt;
    }

    virtual int peek(void)
    {
      int value = -1;
      if (_index < _count)
        value = _buffer[_index];
      return value;
    }

  private:

    MODE     _speed = MODE_100KHz;
    int      _addr  = 0;
    int      _error = 0;
    size_t   _count = 0;
    size_t   _index = 0;
    uint8_t  _buffer[256];
};

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i2c-gpio.h - Software I2C Driver for RP1-GPIO

This program is free software: you can redistribute it and/or

modify it under the terms of the GNU General Public License as

published by the Free Software Foundation, either version 3 of

the License, or at your option) any later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program. If not, see <https://www.gnu.org/licenses/>.

#pragma once

#include "rp1-gpio.h"

class I2C_GPIO

{

public:

typedef enum

{

MODE_100KHz,

MODE_400KHz,

} MODE;

typedef enum

{

STATUS_OK = 0,

STATUS_NAK = -1,

STATUS_BUSY = -2,

STATUS_TIMEOUT = -3,

} STATUS;

I2C_GPIO(RP1_GPIO &gpio, int scl, int sda)

: _gpio(&gpio), _scl(scl), _sda(sda), _spec(SPECS)

{

}

virtual ~I2C_GPIO(void)

{

}

void begin(MODE mode = MODE_100KHz)

{

_spec = &SPECS[mode];

initIO();

}

int write(int addr, const void *buf, size_t len, bool sendStop = true)

{

STATUS rv = STATUS_NAK;

size_t cnt = 0;

if ((addr & ~0x7F) == 0)

{

if ((rv = start()) == STATUS_OK)

{

if ((rv = write((addr << 1) | 0)) == STATUS_OK)

{

const uint8_t *p = (const uint8_t *)buf;

for (; cnt < len; ++cnt)

{

if ((rv = write(*p++)) != STATUS_OK)

break;

}

rv = stop(sendStop, rv);

}

return rv ? rv : cnt;

}

int read(int addr, void *buf, size_t len, bool sendStop = true)

{

STATUS rv = STATUS_NAK;

size_t cnt = 0;

if ((addr & ~0x7F) == 0)

{

if ((rv = start()) == STATUS_OK)

{

if ((rv = write((addr << 1) | 1)) == STATUS_OK)

{

uint8_t b, *p = (uint8_t *)buf;

for (; cnt < len; ++cnt)

{

if ((rv = read(b, cnt + 1 < len)) != STATUS_OK)

break;

*p++ = b;

}

rv = stop(sendStop, rv);

}

return rv ? rv : cnt;

}

int writeAndRead(int addr, const void *wbuf, size_t wlen, void *rbuf, size_t rlen)

{

int rv = 0;

if (wbuf && wlen)

{

if (write(addr, wbuf, wlen, rbuf && rlen ? false : true) < 0)

return 0;

}

if (rbuf && rlen)

rv = read(addr, rbuf, rlen);

return rv;

}

private:

typedef struct {

uint16_t THDSTA, THDDAT, TLOW, THIGH, TSUSTA, TSUSTO, TSUDAT, TBUF;

} spec_t;

static constexpr spec_t SPECS[3] = {

{ 4000, 300, 4700, 4000, 4700, 4000, 250, 4700 }, /* Standard Mode (100KHz) */

{ 600, 0, 1300, 600, 600, 600, 100, 1300 }, /* Fast Mode (400KHz) */

};

static constexpr int LOW = 0;

static constexpr int HIGH = 1;

static constexpr long DELAY_AD = 300L; /* 300ns */

static constexpr long TIMEOUT_CS = 200000000L; /* 200ms */

RP1_GPIO *_gpio;

int _scl;

int _sda;

const spec_t *_spec;

inline void initIO(void)

{

/* Keep signal lines glitch-free */

_gpio->setPullUpDown(_sda, _gpio->PULL_UP);

_gpio->setPullUpDown(_scl, _gpio->PULL_UP);

_gpio->pinMode(_sda, _gpio->OPEN_DRAIN, _gpio->HIGH);

_gpio->pinMode(_scl, _gpio->OPEN_DRAIN, _gpio->HIGH);

}

inline int input(int pin)

{

return _gpio->digitalRead(pin) ? HIGH : LOW;

}

inline void output(int pin, int data)

{

_gpio->digitalWrite(pin, data ? _gpio->HIGH : _gpio->LOW);

}

inline void data(int data)

{

output(_sda, data ? _gpio->HIGH : _gpio->LOW);

}

STATUS clock(int data, bool check = false)

{

output(_scl, data);

/* rising edge ? */

if (data)

{

/* clock stretching */

for (unsigned long t = _gpio->nanos(); input(_scl) == LOW; )

{

if (_gpio->nanos() - t >= TIMEOUT_CS)

return STATUS_TIMEOUT;

}

/* check bus conflicts */

if (check && (input(_sda) == LOW))

return STATUS_BUSY;

}

return STATUS_OK;

}

inline void delay(long ns)

{

if ((ns -= DELAY_AD) > 0)

_gpio->delayNanoseconds(ns);

}

STATUS start(void)

{

if ((input(_sda) == LOW) || (input(_scl) == LOW))

{

delay(_spec->TBUF);

return STATUS_BUSY;

}

data(LOW);

delay(_spec->THDSTA);

if (input(_scl) == LOW)

{

data(HIGH);

delay(_spec->TBUF);

return STATUS_BUSY;

}

clock(LOW);

delay(_spec->THDDAT);

return STATUS_OK;

}

STATUS stop(bool stop, STATUS status)

{

STATUS rv1, rv2;

if (status < STATUS_NAK)

{

data(HIGH);

clock(HIGH);

delay(_spec->TBUF);

}

else if (stop || (status != STATUS_OK))

{

data(LOW);

delay(_spec->TLOW);

rv1 = clock(HIGH);

delay(_spec->TSUSTO);

data(HIGH);

rv2 = input(_sda) == LOW ? STATUS_BUSY : STATUS_OK;

delay(_spec->TBUF);

}

else

{

data(HIGH);

delay(_spec->TSUSTA);

rv1 = rv2 = clock(HIGH, true);

delay(_spec->TSUSTO);

}

return status ? status : (rv1 ? rv1 : rv2);

}

STATUS write(uint8_t b)

{

STATUS rv;

for (uint8_t i = 0x80; i; i >>= 1)

{

data(b & i);

delay(_spec->TLOW);

if ((rv = clock(HIGH, b & i)) != STATUS_OK)

return rv;

delay(_spec->THIGH);

clock(LOW);

delay(_spec->THDDAT);

}

data(HIGH);

delay(_spec->TLOW);

if ((rv = clock(HIGH)) != STATUS_OK)

return rv;

delay(_spec->THIGH);

if (input(_sda))

rv = STATUS_NAK;

clock(LOW);

delay(_spec->THDDAT);

return rv;

}

STATUS read(uint8_t &b, bool ack = true)

{

STATUS rv;

b = 0;

data(HIGH);

for (uint8_t i = 0x80; i; i >>= 1)

{

delay(_spec->TLOW);

if ((rv = clock(HIGH)) != STATUS_OK)

return rv;

delay(_spec->THIGH);

b |= input(_sda) ? i : 0;

clock(LOW);

delay(_spec->THDDAT);

}

if (ack)

data(LOW);

delay(_spec->TLOW);

if ((rv = clock(HIGH)) != STATUS_OK)

return rv;

delay(_spec->THIGH);

clock(LOW);

delay(_spec->THDDAT);

return rv;

}

};

class TwoWire : public I2C_GPIO

{

public:

TwoWire(RP1_GPIO &gpio, int scl, int sda) : I2C_GPIO(gpio, scl, sda)

{

}

virtual ~TwoWire(void)

{

}

void setClock(long speed)

{

_speed = (speed <= 100000 ? MODE_100KHz : MODE_400KHz);

begin();

}

void begin(void)

{

I2C_GPIO::begin(_speed);

}

void end(void)

{

}

void beginTransmission(int address)

{

_addr = address;

_count = 0;

_index = 0;

_error = 0;

}

int endTransmission(bool sendStop = true)

{

if (_error)

return 1; // buffer overflow

int rv = I2C_GPIO::write(_addr, _buffer, _index, sendStop);

if (rv == (int)_index)

return 0; // success

return (rv < 0 ? 2 : 3);

}

int requestFrom(int address, size_t quantity, bool sendStop = true)

{

if (quantity > sizeof(_buffer))

quantity = sizeof(_buffer);

int read = I2C_GPIO::read(address, _buffer, quantity, sendStop);

_count = read > 0 ? read : 0;

_index = 0;

return _count;

}

virtual size_t write(uint8_t data)

{

if (_index >= sizeof(_buffer))

{

_error = 1;

return 0;

}

_buffer[_index++] = data;

return 1;

}

virtual size_t write(const void *buf, size_t len)

{

uint8_t cnt = 0;

const uint8_t *p = (const uint8_t *)buf;

while (len--)

cnt += write(*p++);

return cnt;

}

virtual size_t available(void)

{

return (_index < _count ? _count - _index : 0);

}

virtual int read(void)

{

int value = -1;

if(_index < _count)

value = _buffer[_index++];

return value;

}

virtual size_t readBytes(void *buf, size_t len)

{

uint8_t *p = (uint8_t *)buf;

size_t cnt;

for (cnt = 0; cnt < len; ++cnt)

{

int c = read();

if (c < 0)

break;

*p++ = c;

}

return cnt;

}

virtual int peek(void)

{

int value = -1;

if (_index < _count)

value = _buffer[_index];

return value;

}

private:

MODE _speed = MODE_100KHz;

int _addr = 0;

int _error = 0;

size_t _count = 0;

size_t _index = 0;

uint8_t _buffer[256];

};

投稿

Raspberry Pi 5 のSoftware-I2C libraryを作ってみた。