arduinoでi2c その4

概要

フルスクラッチでmaster書いてみた。

写真

回路図

サンプルコード

# include <inttypes.h>
# include <compat/twi.h>

# define F_CPU 				16000000UL
# define SCL_CLOCK 			50000L
# define PCF8574_ADDRESS		0x27 << 1 + 0
void i2c_init(void)
{
	TWSR = 0;
	TWBR = ((F_CPU / SCL_CLOCK) - 16) / 2;
}
unsigned char i2c_start(unsigned char address)
{
	uint8_t twst;
	TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	twst = TW_STATUS & 0xF8;
	if ((twst != TW_START) && (twst != TW_REP_START)) return 1;
	TWDR = address;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	twst = TW_STATUS & 0xF8;
	if ((twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK)) return 1;
	return 0;
}
void i2c_stop(void)
{
	TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
	while (TWCR & (1 << TWSTO));
}
unsigned char i2c_write(unsigned char data)
{
	uint8_t twst;
	TWDR = data;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	twst = TW_STATUS & 0xF8;
	if (twst != TW_MT_DATA_ACK) return 1;
	return 0;
}
void send(uint8_t d)
{
	uint8_t s;
	i2c_start(PCF8574_ADDRESS);
	i2c_write(d);
	s = d | 0x04;
	i2c_write(s);
	delayMicroseconds(1);
	s = d & 0xfb;
	i2c_write(s);
	delayMicroseconds(1);
	i2c_stop();
}
void set(uint8_t d)
{
	uint8_t s;
	uint8_t f1 = d & 0xf0;
	uint8_t f2 = d << 4;
	i2c_start(PCF8574_ADDRESS);
	s = f1;
	i2c_write(s);
	s = f1 | 0x04;
	i2c_write(s);
	delayMicroseconds(1);
	s = f1 & 0xfb;
	i2c_write(s);
	i2c_stop();
	i2c_start(PCF8574_ADDRESS);
	s = f2;
	i2c_write(s);
	s = f2 | 0x04;
	i2c_write(s);
	delayMicroseconds(1);
	s = f2 & 0xfb;
	i2c_write(s);
	i2c_stop();
}
void data(uint8_t d)
{
	uint8_t s;
	uint8_t f1 = d & 0xf0;
	uint8_t f2 = d << 4;
	i2c_start(PCF8574_ADDRESS);
	s = f1;
	i2c_write(s);
	s = f1 | 0x05;
	i2c_write(s);
	delayMicroseconds(1);
	s = f1 & 0xfa;
	i2c_write(s);
	i2c_stop();
	i2c_start(PCF8574_ADDRESS);
	s = f2;
	i2c_write(s);
	s = f2 | 0x05;
	i2c_write(s);
	delayMicroseconds(1);
	s = f2 & 0xfa | 0x08;
	i2c_write(s);
	i2c_stop();
}
void setup()
{
	unsigned char c;
	unsigned char address;
	int nDevices;
	Serial.begin(115200);
	i2c_init();
	send(0x03);
	delayMicroseconds(50);
	send(0x03);
	delayMicroseconds(50);
	send(0x03);
	delayMicroseconds(15);
	send(0x02);
	set(0x28);
	set(0x0c);
	set(0x01);
	set(0x06);
	data(0x68);
	data(0x65);
	data(0x6c);
	data(0x6c);
	data(0x6f);
	data(0x2c);
	data(0x20);
	data(0x77);
	data(0x6f);
	data(0x72);
	data(0x6c);
	data(0x64);
	data(0x21);
	Serial.println("ok");
}
void loop()
{
	delay(100);
}

以上。