Strange I2C behaviour in V4.2 (release)

[cpehonk]

Hi all,

does anybody encountered the following strange I2C behaviour?

I started to write a small i2c programm controlling a simple 4-line LCD display. Using the typical i2c bus speed of 100kHz leads to an extremly slow i2c communication. The complete master write cycle (using the IDF example "i2c_master_write_slave" function) consumes almost 10ms to complete a one single byte send operation. Changing the frequency of the i2c bus slightly to 150 kHz leads to a dramatic reduce down to 208 microseconds (almost factor 50 !). Does anyone have an explanation for this? What am I doing wrong with 100 kHz?

Best regards,
Christoph

[danhalbert]

We are also seeing this, using ESP-IDF 4.4: https://github.com/adafruit/circuitpython/issues/6263.

[danhalbert]

Same issue as https://www.esp32.com/viewtopic.php?f=12&t=15596