twi.c

用AVR单片机做的一些程序,包括跑马灯显示,PWM产生,ADC转换等

/*
	I2C总线/TWI操作模块
	1、读取和写入函数
	2、地址有效范围255
	3、数据长度为单字节
	4、函数采用查询方式
	5、可直接嵌入到项目中使用
	6、晶振频率：1M
	7、总线速度：50K

	AVR_AFA
	www.iccavr.com
*/

#include "iom128v.h"

/*I2C总线主机模式错误处理*/
void error(unsigned char type) {

	switch (type & 0xF8) {
		case 0x20:					/*址址写失败*/
			/*stop 停止*/
			TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
			break;
		case 0x30:					/*数据写失败*/
			/*stop 停止*/
			TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
			break;
		case 0x38:					/*仲裁失败*/
			break;
		case 0x48:					/*址址读失败*/
			/*stop 停止*/
			TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
			break;
		}
}

/*I2C总线单字节写入*/
unsigned char twi_write(unsigned char addr, unsigned char dd) {

	TWBR = 2;

	/*start 启动*/
	TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x08) {
		error(TWSR);
		return 0;
		}

	/*SLA_W 芯片地址*/
	TWDR = 0xA0;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x18) {
		error(TWSR);
		return 0;
		}

	/*addr 操作地址*/
	TWDR = addr;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x28) {
		error(TWSR);
		return 0;
		}
	
	/*dd 写入数据*/
	TWDR = dd;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x28) {
		error(TWSR);
		return 0;
		}
	
	/*stop 停止*/
	TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
	return 1;
}

/*I2C总线单字节读取*/
unsigned char twi_read(unsigned char addr, unsigned char *dd) {

	TWBR = 2;

	/*start 启动*/
	TWCR=(1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
	while(!(TWCR&(1<<TWINT)));
	if ((TWSR & 0xF8) != 0x08) {
		error(TWSR);
		return 0;
		}

	/*SLA_W 芯片地址*/
	TWDR = 0xA0;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x18) {
		error(TWSR);
		return 0;
		}

	/*addr 操作地址*/
	TWDR = addr;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x28) {
		error(TWSR);
		return 0;
		}
		
	/*start 启动*/
	TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x10) {
		error(TWSR);
		return 0;
		}
	
	/*SLA_R 芯片地址*/
	TWDR = 0xA1;
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x40) {
		error(TWSR);
		return 0;
		}

	/*读取数据*/
	TWCR = (1 << TWINT) | (1 << TWEN);
	while (!(TWCR & (1 << TWINT)));
	if ((TWSR & 0xF8) != 0x58) {
		error(TWSR);
		return 0;
		}
	*dd = TWDR;
		
	/*stop 停止*/
	TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
	return 1;
}