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

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

Raspberry Pi 5のRP1-Chipを使い倒す(GPIO)

【仕様】
・最大通信速度はwrite()のみ5MHz、他は500KHz程度まで。
・データビット数は、1-32ビットに対応
・ビットオーダー対応
・チップセレクト対応(ポラリティ付き)

begin()にて、主要な動作を指定する。

void begin(MODE mode, long speed, int databit = 8, BITORDER bitorder = MSBFIRST, long cs_delay = 1000000);

databit <= 8
write/read/writeAndRead/transferメソッドのbufには1バイト型配列アドレスを指定し、lenにその配列数を指定する。

databit <= 16
write/read/writeAndRead/transferメソッドのbufには2バイト型配列アドレスを指定し、lenにその配列数を指定する。

databit <= 32
write/read/writeAndRead/transferメソッドのbufには4バイト型配列アドレスを指定し、lenにその配列数を指定する。

【使い方のサンプル】

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

RP1_GPIO rp1;

/* with chip-select
   ピン番号を正数指定したときは、Select=LOW, Deselect=HIGH
   ピン番号が負数指定したときは、Select=HIGH, Deselect=LOW
   ※ピン番号0は負数指定できないので注意！
*/
int CS[] = { 8, -7 };
SPI_GPIO spi(rp1, 11, 10, 9, CS, sizeof(CS) / sizeof(CS[0])); 

/* without chip-select */
SPI_GPIO spi(rp1, 11, 10, 9);

int main(int argc, char **argv)
{
  char wbuf[16], rbuf[16];
  rp1.begin();
  spi.begin(spi.MODE3, 1000000); /* MODE3, 1MHz, 8bit, MSBFIRST, CS_DELAY:1000000ns */

  /* simple call (with chip-select) */
  spi.write(0, wbuf, sizeof(wbuf));
  spi.read(0, rbuf, sizeof(rbuf));
  spi.writeAndRead(0, wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));
  spi.transfer(0, wbuf, sizeof(wbuf));

  /* multiple call (with chip-select) */
  spi.select(0);
    spi.write(wbuf, sizeof(wbuf));
    spi.read(rbuf, sizeof(rbuf));
    spi.writeAndRead(wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));
    spi.transfer(wbuf, sizeof(wbuf));
  spi.deselect(0);

  /* multiple call (without chip-select) */
  rp1.pinMode(CS[0], rp1.OUTPUT);
  rp1.digitalWrite(CS[0], rp1.LOW);
  spi.select();
    spi.write(wbuf, sizeof(wbuf));
    spi.read(rbuf, sizeof(rbuf));
    spi.writeAndRead(wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));
    spi.transfer(wbuf, sizeof(wbuf));
  spi.deselect();
  rp1.digitalWrite(CS[0], rp1.HIGH);

  rp1.end();
  return 0;
}

#include <stdio.h>

#include "rp1-gpio.h"

#include "spi-gpio.h"

RP1_GPIO rp1;

/* with chip-select

ピン番号を正数指定したときは、Select=LOW, Deselect=HIGH

ピン番号が負数指定したときは、Select=HIGH, Deselect=LOW

※ピン番号0は負数指定できないので注意！

int CS[] = { 8, -7 };

SPI_GPIO spi(rp1, 11, 10, 9, CS, sizeof(CS) / sizeof(CS[0]));

/* without chip-select */

SPI_GPIO spi(rp1, 11, 10, 9);

int main(int argc, char **argv)

{

char wbuf[16], rbuf[16];

rp1.begin();

spi.begin(spi.MODE3, 1000000); /* MODE3, 1MHz, 8bit, MSBFIRST, CS_DELAY:1000000ns */

/* simple call (with chip-select) */

spi.write(0, wbuf, sizeof(wbuf));

spi.read(0, rbuf, sizeof(rbuf));

spi.writeAndRead(0, wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));

spi.transfer(0, wbuf, sizeof(wbuf));

/* multiple call (with chip-select) */

spi.select(0);

spi.write(wbuf, sizeof(wbuf));

spi.read(rbuf, sizeof(rbuf));

spi.writeAndRead(wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));

spi.transfer(wbuf, sizeof(wbuf));

spi.deselect(0);

/* multiple call (without chip-select) */

rp1.pinMode(CS[0], rp1.OUTPUT);

rp1.digitalWrite(CS[0], rp1.LOW);

spi.select();

spi.write(wbuf, sizeof(wbuf));

spi.read(rbuf, sizeof(rbuf));

spi.writeAndRead(wbuf, sizeof(wbuf), rbuf, sizeof(rbuf));

spi.transfer(wbuf, sizeof(wbuf));

spi.deselect();

rp1.digitalWrite(CS[0], rp1.HIGH);

rp1.end();

return 0;

}

【ライブラリ】

/*
  spi-gpio.h - Software SPI 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 <stdlib.h>
#include <limits.h>
#include "rp1-gpio.h"

class SPI_GPIO
{
  public:

    typedef enum
    {
      MODE0,
      MODE1,
      MODE2,
      MODE3,
    } MODE;

    typedef enum
    {
      LSBFIRST,
      MSBFIRST,
    } BITORDER;

    SPI_GPIO(RP1_GPIO &gpio, int sclk, int mosi, int miso, const int *cspins = nullptr, size_t cssize = 0)
      : _gpio(&gpio), _sclk(sclk), _mosi(mosi), _miso(miso)
    {
      setupCS(cspins, cssize);
    }

    virtual ~SPI_GPIO(void)
    {
    }

    void begin(MODE mode, long speed, int databit = 8, BITORDER bitorder = MSBFIRST, long delay = 1000000)
    {
      _mode  = mode;
      _clock = 1000000000UL / 2 / speed;
      _dbit  = databit > 0 ? databit - 1 : 0;
      _dmsb  = 1 << _dbit;
      _bord  = bitorder;
      _delay = delay;
      initIO();
    }

    int write(int cs, const void *buf, size_t len)
    {
      select(cs);
      int rv = write(buf, len);
      deselect(cs);
      return rv;
    }

    int read(int cs, void *buf, size_t len)
    {
      select(cs);
      int rv = read(buf, len);
      deselect(cs);
      return rv;
    }

    int writeAndRead(int cs, const void *wbuf, size_t wlen, void *rbuf, size_t rlen)
    {
      select(cs);
      int rv = writeAndRead(wbuf, wlen, rbuf, rlen);
      deselect(cs);
      return rv;
    }

    void transfer(int cs, void *buf, size_t len)
    {
      select(cs);
      transfer(buf, len);
      deselect(cs);
    }

    void select(int cs = -1)
    {
      select0(cs, true);
    }

    void deselect(int cs = -1)
    {
      select0(cs, false);
    }

    int write(const void *buf, size_t len)
    {
      if (_dbit < 8)
      {
        const uint8_t *p = (const uint8_t *)buf;
        for (size_t i = 0; i < len; ++i)
          transfer0(p[i], false);
      }
      else if (_dbit < 16)
      {
        const uint16_t *p = (const uint16_t *)buf;
        for (size_t i = 0; i < len; ++i)
          transfer0(p[i], false);
      }
      else
      {
        const uint32_t *p = (const uint32_t *)buf;
        for (size_t i = 0; i < len; ++i)
          transfer0(p[i], false);
      }
      return len;
    }

    int read(void *buf, size_t len)
    {
      if (_dbit < 8)
      {
        uint8_t *p = (uint8_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(0xFFFFFFFF);
      }
      else if (_dbit < 16)
      {
        uint16_t *p = (uint16_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(0xFFFFFFFF);
      }
      else
      {
        uint32_t *p = (uint32_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(0xFFFFFFFF);
      }
      return len;
    }

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

    void transfer(void *buf, size_t len)
    {
      if (_dbit < 8)
      {
        uint8_t *p = (uint8_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(p[i]);
      }
      else if (_dbit < 16)
      {
        uint16_t *p = (uint16_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(p[i]);
      }
      else
      {
        uint32_t *p = (uint32_t *)buf;
        for (size_t i = 0; i < len; ++i)
          p[i] = transfer0(p[i]);
      }
    }

  private:

    static constexpr int CPHA = 1;
    static constexpr int CPOL = 2;

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

    static constexpr long DELAY_AD = 120L; /* 120ns */

    RP1_GPIO *_gpio;
    int       _sclk;
    int       _mosi;
    int       _miso;
    int       _cs[32];
    MODE      _mode;
    long      _clock;
    int       _dbit;
    uint32_t  _dmsb;
    BITORDER  _bord;
    long      _delay;

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

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

    void initIO(void)
    {
      _gpio->pinMode(_sclk, _gpio->INPUT);
      output(_sclk, _mode & CPOL ? HIGH : LOW);
      _gpio->pinMode(_sclk, _gpio->OUTPUT);
      _gpio->pinMode(_mosi, _gpio->OUTPUT);
      _gpio->pinMode(_miso, _gpio->INPUT);
      for (size_t i = 0; i < sizeof(_cs) / sizeof(_cs[0]); ++i)
      {
        int cs = _cs[i];
        if (cs != INT_MIN)
        {
          _gpio->pinMode(abs(cs), _gpio->INPUT);
          outputCS(cs, false);
          _gpio->pinMode(abs(cs), _gpio->OUTPUT);
        }
      }
    }

    void outputCS(int port, bool enable)
    {
      if (port != INT_MIN)
      {
        int data;
        if (port >= 0)
          data = enable ? LOW : HIGH;
        else
          data = enable ? HIGH : LOW;
        output(abs(port), data);
      }
    }

    void setupCS(const int *pins, size_t size)
    {
      for (size_t i = 0; i < sizeof(_cs) / sizeof(_cs[0]); ++i)
        _cs[i] = pins && (i < size) ? pins[i] : INT_MIN;
    }

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

    void select0(int cs, bool enable)
    {
      if (!enable)
      {
        delayNanoseconds(_clock);
        output(_sclk, _mode & CPOL ? HIGH : LOW);
        delayNanoseconds(_delay);
      }
      if ((cs >= 0) && (cs < (int)(sizeof(_cs) / sizeof(_cs[0]))))
        outputCS(_cs[cs], enable);
      if (enable)
      {
        delayNanoseconds(_delay);
        output(_sclk, LOW);
      }
    }

    uint32_t transfer0(uint32_t data, bool read = true)
    {
      input(_sclk); /* good luck charm */
      if ((_mode == MODE0) || (_mode == MODE3))
      {
        delayNanoseconds(_clock);
        for (int i = 0; i <= _dbit; ++i)
        {
          output(_mosi, data & (_bord ? _dmsb : 1));
          delayNanoseconds(_clock);
          output(_sclk, HIGH);
          if (_bord)
            data = (data << 1) | (read ? input(_miso) : 0);
          else
            data = (data >> 1) | (read ? input(_miso) << _dbit : 0);
          delayNanoseconds(_clock);
          output(_sclk, LOW);
        }
      }
      else
      {
        for (int i = 0; i <= _dbit; ++i)
        {
          delayNanoseconds(_clock);
          output(_mosi, data & (_bord ? _dmsb : 1));
          output(_sclk, HIGH);
          delayNanoseconds(_clock);
          if (_bord)
            data = (data << 1) | (read ? input(_miso) : 0);
          else
            data = (data >> 1) | (read ? input(_miso) << _dbit : 0);
          output(_sclk, LOW);
        }
      }
      return data & (_dmsb | (_dmsb - 1));
    }
};

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spi-gpio.h - Software SPI 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 <stdlib.h>

#include <limits.h>

#include "rp1-gpio.h"

class SPI_GPIO

{

public:

typedef enum

{

MODE0,

MODE1,

MODE2,

MODE3,

} MODE;

typedef enum

{

LSBFIRST,

MSBFIRST,

} BITORDER;

SPI_GPIO(RP1_GPIO &gpio, int sclk, int mosi, int miso, const int *cspins = nullptr, size_t cssize = 0)

: _gpio(&gpio), _sclk(sclk), _mosi(mosi), _miso(miso)

{

setupCS(cspins, cssize);

}

virtual ~SPI_GPIO(void)

{

}

void begin(MODE mode, long speed, int databit = 8, BITORDER bitorder = MSBFIRST, long delay = 1000000)

{

_mode = mode;

_clock = 1000000000UL / 2 / speed;

_dbit = databit > 0 ? databit - 1 : 0;

_dmsb = 1 << _dbit;

_bord = bitorder;

_delay = delay;

initIO();

}

int write(int cs, const void *buf, size_t len)

{

select(cs);

int rv = write(buf, len);

deselect(cs);

return rv;

}

int read(int cs, void *buf, size_t len)

{

select(cs);

int rv = read(buf, len);

deselect(cs);

return rv;

}

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

{

select(cs);

int rv = writeAndRead(wbuf, wlen, rbuf, rlen);

deselect(cs);

return rv;

}

void transfer(int cs, void *buf, size_t len)

{

select(cs);

transfer(buf, len);

deselect(cs);

}

void select(int cs = -1)

{

select0(cs, true);

}

void deselect(int cs = -1)

{

select0(cs, false);

}

int write(const void *buf, size_t len)

{

if (_dbit < 8)

{

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

for (size_t i = 0; i < len; ++i)

transfer0(p[i], false);

}

else if (_dbit < 16)

{

const uint16_t *p = (const uint16_t *)buf;

for (size_t i = 0; i < len; ++i)

transfer0(p[i], false);

}

else

{

const uint32_t *p = (const uint32_t *)buf;

for (size_t i = 0; i < len; ++i)

transfer0(p[i], false);

}

return len;

}

int read(void *buf, size_t len)

{

if (_dbit < 8)

{

uint8_t *p = (uint8_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(0xFFFFFFFF);

}

else if (_dbit < 16)

{

uint16_t *p = (uint16_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(0xFFFFFFFF);

}

else

{

uint32_t *p = (uint32_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(0xFFFFFFFF);

}

return len;

}

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

{

int rv = 0;

if (wbuf && wlen)

write(wbuf, wlen);

if (rbuf && rlen)

rv = read(rbuf, rlen);

return rv;

}

void transfer(void *buf, size_t len)

{

if (_dbit < 8)

{

uint8_t *p = (uint8_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(p[i]);

}

else if (_dbit < 16)

{

uint16_t *p = (uint16_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(p[i]);

}

else

{

uint32_t *p = (uint32_t *)buf;

for (size_t i = 0; i < len; ++i)

p[i] = transfer0(p[i]);

}

private:

static constexpr int CPHA = 1;

static constexpr int CPOL = 2;

static constexpr int LOW = 0;

static constexpr int HIGH = 1;

static constexpr long DELAY_AD = 120L; /* 120ns */

RP1_GPIO *_gpio;

int _sclk;

int _mosi;

int _miso;

int _cs[32];

MODE _mode;

long _clock;

int _dbit;

uint32_t _dmsb;

BITORDER _bord;

long _delay;

inline void output(int port, int data)

{

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

}

inline int input(int port)

{

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

}

void initIO(void)

{

_gpio->pinMode(_sclk, _gpio->INPUT);

output(_sclk, _mode & CPOL ? HIGH : LOW);

_gpio->pinMode(_sclk, _gpio->OUTPUT);

_gpio->pinMode(_mosi, _gpio->OUTPUT);

_gpio->pinMode(_miso, _gpio->INPUT);

for (size_t i = 0; i < sizeof(_cs) / sizeof(_cs[0]); ++i)

{

int cs = _cs[i];

if (cs != INT_MIN)

{

_gpio->pinMode(abs(cs), _gpio->INPUT);

outputCS(cs, false);

_gpio->pinMode(abs(cs), _gpio->OUTPUT);

}

void outputCS(int port, bool enable)

{

if (port != INT_MIN)

{

int data;

if (port >= 0)

data = enable ? LOW : HIGH;

else

data = enable ? HIGH : LOW;

output(abs(port), data);

}

void setupCS(const int *pins, size_t size)

{

for (size_t i = 0; i < sizeof(_cs) / sizeof(_cs[0]); ++i)

_cs[i] = pins && (i < size) ? pins[i] : INT_MIN;

}

inline void delayNanoseconds(long ns)

{

if ((ns -= DELAY_AD) > 0)

_gpio->delayNanoseconds(ns);

}

void select0(int cs, bool enable)

{

if (!enable)

{

delayNanoseconds(_clock);

output(_sclk, _mode & CPOL ? HIGH : LOW);

delayNanoseconds(_delay);

}

if ((cs >= 0) && (cs < (int)(sizeof(_cs) / sizeof(_cs[0]))))

outputCS(_cs[cs], enable);

if (enable)

{

delayNanoseconds(_delay);

output(_sclk, LOW);

}

uint32_t transfer0(uint32_t data, bool read = true)

{

input(_sclk); /* good luck charm */

if ((_mode == MODE0) || (_mode == MODE3))

{

delayNanoseconds(_clock);

for (int i = 0; i <= _dbit; ++i)

{

output(_mosi, data & (_bord ? _dmsb : 1));

delayNanoseconds(_clock);

output(_sclk, HIGH);

if (_bord)

data = (data << 1) | (read ? input(_miso) : 0);

else

data = (data >> 1) | (read ? input(_miso) << _dbit : 0);

delayNanoseconds(_clock);

output(_sclk, LOW);

}

else

{

for (int i = 0; i <= _dbit; ++i)

{

delayNanoseconds(_clock);

output(_mosi, data & (_bord ? _dmsb : 1));

output(_sclk, HIGH);

delayNanoseconds(_clock);

if (_bord)

data = (data << 1) | (read ? input(_miso) : 0);

else

data = (data >> 1) | (read ? input(_miso) << _dbit : 0);

output(_sclk, LOW);

}

return data & (_dmsb | (_dmsb - 1));

}

};

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