I2C repeated start broken

[Erriez]

The following example reads zero's when generating an I2C repeated start:

#include <Arduino.h>
#include <Wire.h>

#define DS3231_ADDR             (0xD0 >> 1)

void setup()
{
    Serial.begin(115200);
    Serial.println();

    Wire.begin();
    Wire.setClock(400000);
}

void loop()
{
    Wire.beginTransmission(DS3231_ADDR);
    Wire.write((uint8_t)0x0);
    Wire.endTransmission(false); // < Generate repeated start with false
    Wire.requestFrom((uint8_t)DS3231_ADDR, (uint8_t)7, true);
    while(Wire.available()) {
        Serial.printf("0x%02X ", Wire.read());
    }
    Serial.println();

    delay(1000);
}

Incorrect output of the example above with a repeated start Wire.endTransmission(false);: 0x00 0x00 0x00 0x00 0x00 0x00 0x00

Valid data is set on the I2C bus with a repeated start, but the receive data is not read correctly in the ESP32 I2C driver. Screenshot valid I2C signals measured with a logic analyzer:

Valid ouput when change repeated start to a stop - start condition Wire.endTransmission(true);: 0x17 0x47 0x21 0x07 0x29 0x07 0x18

This bug is already fixed in the official Espressif branch: https://github.com/espressif/arduino-esp32/commit/b05430cfd9f273d627baa6c4dac6c215d6cde902#diff-64fd3b24e81f73a1c0e49b5738154bc8

Sources: https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-i2c.c https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-i2c.h https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.cpp https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.h

Replacing the sources above works. Can someone backport this?

[ivankravets]

Does it work with upstream version? http://docs.platformio.org/en/latest/platforms/espressif32.html#stable-and-upstream-versions

[Erriez]

Unfortunately, it does not work with this upstream branch: It reads only zero's as well.

Wire.endTransmission(false); // < Generate repeated start with false reads only zero's
Wire.endTransmission(true); // < Generate new start with true works

[alborzs]

Stumbled upon this issue while trying to find out why my BNO055 (9DoF sensor) was suddenly returning only zeros after updating to 1.5.0. Is there a workaround for us to use in the meanwhile?

[Erriez]

Stumbled upon this issue while trying to find out why my BNO055 (9DoF sensor) was suddenly returning only zeros after updating to 1.5.0. Is there a workaround for us to use in the meanwhile?

I suggest you to overwrite the existing sources from the ESP32 master branch (as workaround):

https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-i2c.c https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-i2c.h https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.cpp https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.h

[ivankravets]

Should be fixed in Arduino ESP32 core. See docs how you can switch to development version of this framework https://docs.platformio.org/en/latest/platforms/espressif32.html#using-arduino-framework-with-staging-version

[glucee]

I think the problem is still there, could you check it @ivankravets

[ivankravets]

Do you use the latest version of dev/platform? Please open PlatformIO IDE Terminal and type pio update.

[ivankravets]

If you still experience this issue, please report to https://github.com/espressif/arduino-esp32/issues