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Double I2C read in one transaction skips a clock pulse (#5528) #6579

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Double I2C read in one transaction skips a clock pulse (#5528) #6579

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0ec1fa5
Double I2C read in one transaction skips a clock pulse (#5528)
TD-er Oct 1, 2019
5e677f6
Merge branch 'master' into bugfix/issue5528_I2C
TD-er Oct 3, 2019
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42 changes: 28 additions & 14 deletions cores/esp8266/core_esp8266_si2c.cpp
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Expand Up @@ -197,38 +197,39 @@ static bool twi_write_start(void) {
return true;
}

static void ICACHE_RAM_ATTR twi_wait_clockStretchLimit() {
uint32_t t=0; while(SCL_READ()==0 && (t++)<twi_clockStretchLimit); // twi_clockStretchLimit
}

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_wait_clockStretchLimit();
twi_delay(twi_dcount);
SDA_HIGH();
twi_delay(twi_dcount);
return true;
}

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_wait_clockStretchLimit();
twi_delay(twi_dcount);
return true;
}

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
twi_wait_clockStretchLimit();
bool bit = SDA_READ();
twi_delay(twi_dcount);
return bit;
Expand All @@ -251,6 +252,13 @@ static unsigned char twi_read_byte(bool nack) {
return byte;
}

// Generate a clock "valey" (at the end of a segment, just before a repeated start)
void twi_scl_valey( void ) {
SCL_LOW();
twi_delay(twi_dcount);
SCL_HIGH();
}

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
Expand All @@ -265,12 +273,15 @@ unsigned char twi_writeTo(unsigned char address, unsigned char * buf, unsigned i
}
}
if(sendStop) twi_write_stop();
else {
twi_scl_valey();
twi_wait_clockStretchLimit();
// TD-er: Also twi_delay here?
// twi_delay(twi_dcount);
}
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_scl_valey();
twi_delay(twi_dcount);
}
return 0;
Expand All @@ -286,12 +297,15 @@ unsigned char twi_readFrom(unsigned char address, unsigned char* buf, unsigned i
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();
else {
twi_scl_valey();
twi_wait_clockStretchLimit();
// TD-er: Also twi_delay here?
// twi_delay(twi_dcount);
}
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_scl_valey();
twi_delay(twi_dcount);
}
return 0;
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