uint8_t twi_status() {
if (SCL_READ() == 0)
return I2C_SCL_HELD_LOW; // SCL held low by another device, no procedure available to recover
int clockCount = 20;
while (SDA_READ() == 0 && clockCount-- > 0) { // if SDA low, read the bits slaves have to sent to a max
twi_read_bit();
if (SCL_READ() == 0) {
return I2C_SCL_HELD_LOW_AFTER_READ; // I2C bus error. SCL held low beyond slave clock stretch time
}
}
if (SDA_READ() == 0)
return I2C_SDA_HELD_LOW; // I2C bus error. SDA line held low by slave/another_master after n bits.
if (!twi_write_start())
return I2C_SDA_HELD_LOW_AFTER_INIT; // line busy. SDA again held low by another device. 2nd master?
return I2C_OK;
}
static bool twi_read_bit(void) {
uint32_t i = 0;
SCL_LOW();
SDA_HIGH();
twi_delay(twi_dcount+2);
SCL_HIGH();
while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit);// Clock stretching
bool bit = SDA_READ();
twi_delay(twi_dcount);
return bit;
}
static bool twi_write_bit(bool bit) {
uint32_t i = 0;
SCL_LOW();
if (bit) SDA_HIGH();
else SDA_LOW();
twi_delay(twi_dcount+1);
SCL_HIGH();
while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit);// Clock stretching
twi_delay(twi_dcount);
return true;
}
static bool ICACHE_FLASH_ATTR twi_read_bit()
{
unsigned int i = 0;
SCL_LOW();
SDA_HIGH();
twi_delay(twi_dcount + 2);
SCL_HIGH();
while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit); // Clock stretching
bool bit = SDA_READ();
twi_delay(twi_dcount);
return bit;
}
static bool twi_write_stop(void){
uint32_t i = 0;
SCL_LOW();
SDA_LOW();
twi_delay(twi_dcount);
SCL_HIGH();
while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit); // Clock stretching
twi_delay(twi_dcount);
SDA_HIGH();
twi_delay(twi_dcount);
return true;
}
static bool ICACHE_FLASH_ATTR twi_write_stop(void)
{
unsigned int i = 0;
SCL_LOW();
SDA_LOW();
twi_delay(twi_dcount);
SCL_HIGH();
while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit); // Clock stretching
twi_delay(twi_dcount);
SDA_HIGH();
twi_delay(twi_dcount);
return true;
}
unsigned char twi_readFrom(unsigned char address, unsigned char* buf, unsigned int len, unsigned char sendStop){
unsigned int i;
if(!twi_write_start()) return 4;//line busy
if(!twi_write_byte(((address << 1) | 1) & 0xFF)) {
if (sendStop) twi_write_stop();
return 2;//received NACK on transmit of address
}
for(i=0; i<(len-1); i++) buf[i] = twi_read_byte(false);
buf[len-1] = twi_read_byte(true);
if(sendStop) twi_write_stop();
i = 0;
while(SDA_READ() == 0 && (i++) < 10){
SCL_LOW();
twi_delay(twi_dcount);
SCL_HIGH();
unsigned int t=0; while(SCL_READ()==0 && (t++)<twi_clockStretchLimit); // twi_clockStretchLimit
twi_delay(twi_dcount);
}
return 0;
}
unsigned char twi_writeTo(unsigned char address, unsigned char * buf, unsigned int len, unsigned char sendStop){
unsigned int i;
if(!twi_write_start()) return 4;//line busy
if(!twi_write_byte(((address << 1) | 0) & 0xFF)) {
if (sendStop) twi_write_stop();
return 2; //received NACK on transmit of address
}
for(i=0; i<len; i++) {
if(!twi_write_byte(buf[i])) {
if (sendStop) twi_write_stop();
return 3;//received NACK on transmit of data
}
}
if(sendStop) twi_write_stop();
i = 0;
while(SDA_READ() == 0 && (i++) < 10){
SCL_LOW();
twi_delay(twi_dcount);
SCL_HIGH();
unsigned int t=0; while(SCL_READ()==0 && (t++)<twi_clockStretchLimit); // twi_clockStretchLimit
twi_delay(twi_dcount);
}
return 0;
}
void ICACHE_RAM_ATTR onSdaChange(void)
{
static uint8_t sda;
static uint8_t scl;
sda = SDA_READ();
scl = SCL_READ();
switch (twip_state)
{
case TWIP_IDLE:
if (!scl) {
// DATA - ignore
} else if (sda) {
// STOP - ignore
} else {
// START
bitCount = 8;
twip_state = TWIP_START;
ets_timer_arm_new(&timer, twi_timeout_ms, false, true); // Once, ms
}
break;
case TWIP_START:
case TWIP_REP_START:
case TWIP_SEND_ACK:
case TWIP_WAIT_ACK:
case TWIP_SLA_R:
case TWIP_REC_ACK:
case TWIP_READ_ACK:
case TWIP_RWAIT_ACK:
case TWIP_WRITE:
if (!scl) {
// DATA - ignore
} else {
// START or STOP
SDA_HIGH(); // Should not be necessary
twip_status = TW_BUS_ERROR;
twi_onTwipEvent(twip_status);
twip_mode = TWIPM_WAIT;
twip_state = TWIP_BUS_ERR;
}
break;
case TWIP_WAIT_STOP:
case TWIP_BUS_ERR:
if (!scl) {
// DATA - ignore
} else {
if (sda) {
// STOP
SCL_LOW(); // clock stretching
ets_timer_disarm(&timer);
twip_state = TWIP_IDLE;
twip_mode = TWIPM_IDLE;
SCL_HIGH();
} else {
// START
if (twip_state == TWIP_BUS_ERR) {
// ignore
} else {
bitCount = 8;
twip_state = TWIP_REP_START;
ets_timer_arm_new(&timer, twi_timeout_ms, false, true); // Once, ms
}
}
}
break;
case TWIP_SLA_W:
case TWIP_READ:
if (!scl) {
// DATA - ignore
} else {
// START or STOP
if (bitCount != 7) {
// inside byte transfer - error
twip_status = TW_BUS_ERROR;
twi_onTwipEvent(twip_status);
twip_mode = TWIPM_WAIT;
twip_state = TWIP_BUS_ERR;
} else {
// during first bit in byte transfer - ok
SCL_LOW(); // clock stretching
twip_status = TW_SR_STOP;
twi_onTwipEvent(twip_status);
if (sda) {
// STOP
ets_timer_disarm(&timer);
twip_state = TWIP_IDLE;
twip_mode = TWIPM_IDLE;
} else {
// START
bitCount = 8;
ets_timer_arm_new(&timer, twi_timeout_ms, false, true); // Once, ms
twip_state = TWIP_REP_START;
twip_mode = TWIPM_IDLE;
}
}
}
break;
default:
break;
}
}
void ICACHE_RAM_ATTR onSclChange(void)
{
static uint8_t sda;
static uint8_t scl;
sda = SDA_READ();
scl = SCL_READ();
twip_status = 0xF8; // reset TWI status
switch (twip_state)
{
case TWIP_IDLE:
case TWIP_WAIT_STOP:
case TWIP_BUS_ERR:
// ignore
break;
case TWIP_START:
case TWIP_REP_START:
case TWIP_SLA_W:
case TWIP_READ:
if (!scl) {
// ignore
} else {
bitCount--;
twi_data <<= 1;
twi_data |= sda;
if (bitCount != 0) {
// continue
} else {
twip_state = TWIP_SEND_ACK;
}
}
break;
case TWIP_SEND_ACK:
if (scl) {
// ignore
} else {
if (twip_mode == TWIPM_IDLE) {
if ((twi_data & 0xFE) != twi_addr) {
// ignore
} else {
SDA_LOW();
}
} else {
if (!twi_ack) {
// ignore
} else {
SDA_LOW();
}
}
twip_state = TWIP_WAIT_ACK;
}
break;
case TWIP_WAIT_ACK:
if (scl) {
// ignore
} else {
if (twip_mode == TWIPM_IDLE) {
if ((twi_data & 0xFE) != twi_addr) {
SDA_HIGH();
twip_state = TWIP_WAIT_STOP;
} else {
SCL_LOW(); // clock stretching
SDA_HIGH();
twip_mode = TWIPM_ADDRESSED;
if (!(twi_data & 0x01)) {
twip_status = TW_SR_SLA_ACK;
twi_onTwipEvent(twip_status);
bitCount = 8;
twip_state = TWIP_SLA_W;
} else {
twip_status = TW_ST_SLA_ACK;
twi_onTwipEvent(twip_status);
twip_state = TWIP_SLA_R;
}
}
} else {
SCL_LOW(); // clock stretching
SDA_HIGH();
if (!twi_ack) {
twip_status = TW_SR_DATA_NACK;
twi_onTwipEvent(twip_status);
twip_mode = TWIPM_WAIT;
twip_state = TWIP_WAIT_STOP;
} else {
twip_status = TW_SR_DATA_ACK;
twi_onTwipEvent(twip_status);
bitCount = 8;
twip_state = TWIP_READ;
}
}
}
break;
case TWIP_SLA_R:
case TWIP_WRITE:
if (scl) {
// ignore
} else {
bitCount--;
(twi_data & 0x80) ? SDA_HIGH() : SDA_LOW();
twi_data <<= 1;
if (bitCount != 0) {
// continue
} else {
twip_state = TWIP_REC_ACK;
}
}
break;
case TWIP_REC_ACK:
if (scl) {
// ignore
} else {
SDA_HIGH();
twip_state = TWIP_READ_ACK;
}
break;
case TWIP_READ_ACK:
if (!scl) {
// ignore
} else {
twi_ack_rec = !sda;
twip_state = TWIP_RWAIT_ACK;
}
break;
case TWIP_RWAIT_ACK:
if (scl) {
// ignore
} else {
SCL_LOW(); // clock stretching
if (twi_ack && twi_ack_rec) {
twip_status = TW_ST_DATA_ACK;
twi_onTwipEvent(twip_status);
twip_state = TWIP_WRITE;
} else {
// we have no more data to send and/or the master doesn't want anymore
twip_status = twi_ack_rec ? TW_ST_LAST_DATA : TW_ST_DATA_NACK;
twi_onTwipEvent(twip_status);
twip_mode = TWIPM_WAIT;
twip_state = TWIP_WAIT_STOP;
}
}
break;
default:
break;
}
}