结构及宏定义
struct i2c {
unsigned int scl;
unsigned int sda;
};
#define I2C_ACK 0 /* PD_SDA level to ack a byte */
#define I2C_NOACK 1 /* PD_SDA level to noack a byte */
#define CONFIG_SOFT_I2C_READ_REPEATED_START各函数详细实现
clock动作函数
void i2c_scl(struct i2c *i2c,int bit)
{
gpio_direction_output(i2c->scl, bit);
}
data动作函数
这里需要注意的是，当i2c master想要让data为高，是把data的gpio设置为输入，这是因为SCL和SDA都是默认硬件上拉的。同时也是为了master写完数据以后去获取ACK。
void i2c_sda(struct i2c *i2c, int bit)
{
if (bit) {
gpio_direction_input(i2c->sda);
} else {
gpio_direction_output(i2c->sda, bit);
}
}
获取data线的状态
int i2c_read_sda(struct i2c *i2c)
{
return gpio_get_value(i2c->sda);
}
start函数
/*-----------------------------------------------------------------------
* START: High -> Low on SDA while SCL is High
*/
void send_start(struct i2c *i2c)
{
udelay(5);
i2c_sda(i2c, 1);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
i2c_sda(i2c, 0);
udelay(5);
}
stop函数
/*-----------------------------------------------------------------------
* STOP: Low -> High on SDA while SCL is High
*/
static void send_stop(struct i2c *i2c)
{
i2c_scl(i2c, 0);
udelay(5);
i2c_sda(i2c, 0);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
i2c_sda(i2c, 1);
udelay(5);
}
reset函数
/*-----------------------------------------------------------------------
* Send a reset sequence consisting of 9 clocks with the data signal high
* to clock any confused device back into an idle state. Also send a
* <stop> at the end of the sequence for belts & suspenders.
*/
void send_reset(struct i2c *i2c)
{
int j;
i2c_scl(i2c, 1);
i2c_sda(i2c, 1);
for (j = 0; j < 9; j++) {
i2c_scl(i2c, 0);
udelay(5);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
udelay(5);
}
send_stop(i2c);
}
ACK函数
ACK: send_ack(i2c, 0)
NOACK: send_ack(i2c, 1)
/*-----------------------------------------------------------------------
* ack should be I2C_ACK or I2C_NOACK
*/
void send_ack(struct i2c *i2c, int ack)
{
i2c_scl(i2c, 0);
udelay(5);
i2c_sda(i2c, ack);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
udelay(5);
i2c_scl(i2c, 0);
udelay(5);
}
i2c写1byte函数
/*-----------------------------------------------------------------------
* Send 8 bits and look for an acknowledgement.
*/
int write_byte(struct i2c *i2c,unsigned char data)
{
int j;
int nack;
for (j = 0; j < 8; j++) {
i2c_scl(i2c, 0);
udelay(5);
i2c_sda(i2c,data & 0x80);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
udelay(5);
data <<= 1;
}
/*
* Look for an <ACK>(negative logic) and return it.
*/
i2c_scl(i2c, 0);
udelay(5);
i2c_sda(i2c, 1);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
udelay(5);
nack = i2c_read_sda(i2c);
i2c_scl(i2c, 0);
udelay(5);
return(nack); /* not a nack is an ack */
}
i2c读1byte函数
/*-----------------------------------------------------------------------
* if ack == I2C_ACK, ACK the byte so can continue reading, else
* send I2C_NOACK to end the read.
*/
static unsigned char read_byte(struct i2c *i2c,int ack)
{
int data;
int j;
/*
* Read 8 bits, MSB first.
*/
i2c_sda(i2c, 1);
data = 0;
for (j = 0; j < 8; j++) {
i2c_scl(i2c, 0);
udelay(5);
i2c_scl(i2c, 1);
udelay(5);
data <<= 1;
data |= i2c_read_sda(i2c);
udelay(5);
}
send_ack(i2c, ack);
return(data);
}
i2c初始化函数
i2c->scl、i2c->sda分别为clock和data数据线的GPIO号。
/*-----------------------------------------------------------------------
* Initialization
*/
void i2c_init(struct i2c *i2c)
{
gpio_request(i2c->scl, "soft_i2c");
gpio_request(i2c->sda, "soft_i2c");
gpio_direction_output(i2c->sda, 1);
gpio_direction_output(i2c->scl, 1);
send_reset(i2c);
}
i2c读len个字节函数
参数释义
chip：从设备地址
addr: 从设备寄存器地址
alen: 从设备寄存器地址的长度
buffer: 存放读取的数据的buffer
len: 读取len个字节
/*-----------------------------------------------------------------------
* Read bytes
*/
int i2c_read(struct i2c *i2c, unsigned char chip,
unsigned int addr, int alen, unsigned char *buffer, int len)
{
int shift;
#ifdef DEBUG
printf("i2c_read: chip %x addr %x alen %d buffer %p len %d\n",
chip, addr, alen, buffer, len);
#endif
/*
* Do the addressing portion of a write cycle to set the
* chip's address pointer. If the address length is zero,
* don't do the normal write cycle to set the address pointer,
* there is no address pointer in this chip.
*/
send_start(i2c);
if (alen > 0) {
if (write_byte(i2c,chip << 1)) { /* write cycle */
send_stop(i2c);
printf("i2c_read, no chip responded %02X\n", chip);
return(1);
}
shift = (alen-1) * 8;
while(alen-- > 0) {
if(write_byte(i2c,addr >> shift)) {
printf("i2c_read, address not <ACK>ed\n");
return(1);
}
shift -= 8;
}
/* Some I2C chips need a stop/start sequence here,
* other chips don't work with a full stop and need
* only a start. Default behaviour is to send the
* stop/start sequence.
*/
#ifdef CONFIG_SOFT_I2C_READ_REPEATED_START
send_start(i2c);
#else
send_stop(i2c);
send_start(i2c);
#endif
}
/*
* Send the chip address again, this time for a read cycle.
* Then read the data. On the last byte, we do a NACK instead
* of an ACK(len == 0) to terminate the read.
*/
write_byte(i2c,(chip << 1) | 1); /* read cycle */
while (len-- > 0) {
*buffer++ = read_byte(i2c,len == 0);
}
send_stop(i2c);
return(0);
}
i2c写len个字节函数
参数释义
chip：从设备地址
addr: 从设备寄存器地址
alen: 从设备寄存器地址的长度
buffer: 存放要写入的数据
len: 写len个字节
/*----------------------------------------------------------------------- * Write bytes */ int i2c_write(struct i2c *i2c, unsigned char chip,
unsigned int addr, int alen, unsigned char *buffer, int len) { int shift, failures = 0; #ifdef DEBUG printf("i2c_write: chip %x addr %x alen %d buffer %p len %d\n", chip, addr, alen, buffer, len); #endif send_start(i2c); if (write_byte(i2c, chip << 1)) { /* write cycle */ send_stop(i2c); printf("i2c_write, no chip responded %02X\n", chip); return(1); } shift = (alen-1) * 8; while (alen-- > 0) { if (write_byte(i2c, addr >> shift)) { printf("i2c_write, address not <ACK>ed\n"); return(1); } shift -= 8; } while (len-- > 0) { if (write_byte(i2c,*buffer++)) { failures++; } } send_stop(i2c); return(failures); }
i2c探测函数
返回0代表此i2c总线上有地址为addr的设备
返回1代表此i2c总线上没侦测到从设备地址为addr的设备
int i2c_probe(struct i2c *i2c, unsigned char addr)
{
int rc;
send_start(i2c);
rc = write_byte(i2c, (addr << 1) | 0);
send_stop(i2c);
printf("i2c probe:%d, addr:%x\n", rc, addr);
return (rc ? 1 : 0);
}
标签：scl,int,udelay,send,sda,GPIO,i2c,模拟 From： https://www.cnblogs.com/wanglouxiaozi/p/16944487.html