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added clock stretch yield, [issue 2162] fixed twi::status #6860

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Dec 1, 2019
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added clock stretch yield, [issue 2162] fixed twi::status #6860

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18 changes: 9 additions & 9 deletions cores/esp8266/core_esp8266_si2c.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
#include "twi.h"
#include "pins_arduino.h"
#include "wiring_private.h"
#include "PolledTimeout.h"



Expand Down Expand Up @@ -122,9 +123,12 @@ class Twi
// Handle the case where a slave needs to stretch the clock with a time-limited busy wait
inline void WAIT_CLOCK_STRETCH()
{
for (unsigned int t = 0; !SCL_READ() && (t < twi_clockStretchLimit); t++)
{
/* noop */
esp8266::polledTimeout::oneShotFastUs timeout(twi_clockStretchLimit);
esp8266::polledTimeout::periodicFastUs yieldTimeout(5000);
while(!timeout && !SCL_READ()) // outer loop is stretch duration up to stretch limit
{
if (yieldTimeout) // inner loop yields every 5ms
yield();
}
}

Expand Down Expand Up @@ -245,7 +249,7 @@ void Twi::init(unsigned char sda, unsigned char scl)
pinMode(twi_sda, INPUT_PULLUP);
pinMode(twi_scl, INPUT_PULLUP);
twi_setClock(preferred_si2c_clock);
twi_setClockStretchLimit(230); // default value is 230 uS
twi_setClockStretchLimit(150000L); // default value is 150 mS
}

void Twi::setAddress(uint8_t address)
Expand Down Expand Up @@ -444,6 +448,7 @@ unsigned char Twi::readFrom(unsigned char address, unsigned char* buf, unsigned

uint8_t Twi::status()
{
WAIT_CLOCK_STRETCH(); // wait for a slow slave to finish
if (!SCL_READ())
{
return I2C_SCL_HELD_LOW; // SCL held low by another device, no procedure available to recover
Expand All @@ -463,11 +468,6 @@ uint8_t Twi::status()
return I2C_SDA_HELD_LOW; // I2C bus error. SDA line held low by slave/another_master after n bits.
}

if (!write_start())
{
return I2C_SDA_HELD_LOW_AFTER_INIT; // line busy. SDA again held low by another device. 2nd master?
}

return I2C_OK;
}

Expand Down