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。
Raspberry Pi 5のRP1-Chipを使い倒す(GPIO)
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】
・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】
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#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)】
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#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; } |
【ライブラリ】
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/* 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_NO_DEVICE = -4, } 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_NO_DEVICE; 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_NO_DEVICE; 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->pinMode(_sda, _gpio->INPUT); _gpio->pinMode(_scl, _gpio->INPUT); output(_sda, HIGH); output(_scl, HIGH); _gpio->setPullUpDown(_sda, _gpio->PULL_UP); _gpio->setPullUpDown(_scl, _gpio->PULL_UP); _gpio->pinMode(_sda, _gpio->OPEN_DRAIN); _gpio->pinMode(_scl, _gpio->OPEN_DRAIN); } inline int input(int port) { return _gpio->digitalRead(port) ? HIGH : LOW; } inline void output(int port, int data) { _gpio->digitalWrite(port, data ? _gpio->HIGH : _gpio->LOW); } inline void outputL(int port) { output(port, LOW); } STATUS outputH(int port) { output(port, HIGH); /* clock stretching */ if (port == _scl) { for (unsigned long t = _gpio->nanos(); input(port) == LOW; ) { if (_gpio->nanos() - t >= TIMEOUT_CS) return STATUS_TIMEOUT; } } /* check bus conflicts */ else if (port == _sda) { if (input(port) == LOW) return STATUS_BUSY; } return STATUS_OK; } inline void delayNanoseconds(long ns) { if ((ns -= DELAY_AD) > 0) _gpio->delayNanoseconds(ns); } STATUS start(void) { if ((input(_sda) == LOW) || (input(_scl) == LOW)) { delayNanoseconds(_spec->TBUF); return STATUS_BUSY; } output(_scl, HIGH); outputL(_sda); delayNanoseconds(_spec->THDSTA); outputL(_scl); delayNanoseconds(_spec->THDDAT); return STATUS_OK; } STATUS stop(bool stop, STATUS status) { STATUS rv1, rv2; if (status < STATUS_NAK) { output(_sda, HIGH); output(_scl, HIGH); delayNanoseconds(_spec->TBUF); } else if (stop || (status != STATUS_OK)) { outputL(_sda); delayNanoseconds(_spec->TLOW); rv1 = outputH(_scl); delayNanoseconds(_spec->TSUSTO); rv2 = outputH(_sda); delayNanoseconds(_spec->TBUF); } else { output(_sda, HIGH); delayNanoseconds(_spec->TSUSTA); rv1 = outputH(_scl); delayNanoseconds(_spec->TSUSTO); rv2 = STATUS_OK; } return status ? status : (rv1 ? rv1 : rv2); } STATUS write(uint8_t b) { STATUS rv; for (uint8_t i = 0x80; i; i >>= 1) { output(_sda, b & i); delayNanoseconds(_spec->TLOW); if ((rv = outputH(_scl)) != STATUS_OK) return rv; if ((b & i) && (input(_sda) == LOW)) return STATUS_BUSY; delayNanoseconds(_spec->THIGH); outputL(_scl); delayNanoseconds(_spec->THDDAT); } output(_sda, HIGH); delayNanoseconds(_spec->TLOW); if ((rv = outputH(_scl)) != STATUS_OK) return rv; delayNanoseconds(_spec->THIGH); if (input(_sda)) rv = STATUS_NAK; outputL(_scl); delayNanoseconds(_spec->THDDAT); return rv; } STATUS read(uint8_t &b, bool ack = true) { STATUS rv; b = 0; output(_sda, HIGH); for (uint8_t i = 0x80; i; i >>= 1) { delayNanoseconds(_spec->TLOW); if ((rv = outputH(_scl)) != STATUS_OK) return rv; delayNanoseconds(_spec->THIGH); b |= input(_sda) ? i : 0; outputL(_scl); delayNanoseconds(_spec->THDDAT); } if (ack) outputL(_sda); delayNanoseconds(_spec->TLOW); if ((rv = outputH(_scl)) != STATUS_OK) return rv; delayNanoseconds(_spec->THIGH); outputL(_scl); delayNanoseconds(_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; begin(); } void begin(void) { if (_speed <= 100000) I2C_GPIO::begin(MODE_100KHz); else I2C_GPIO::begin(MODE_400KHz); } 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: long _speed = 100000; int _addr = 0; int _error = 0; size_t _count = 0; size_t _index = 0; uint8_t _buffer[256]; }; |