I2C Master Wire.requestFrom timeout not obeyed, takes a whole second to read when slave is not present

[leifclaesson]

What you are trying to do?
I'm trying to read from an I2C device which is not always present.
With ESP32 Arduino 1.0.6, the read fails instantly as it should. With 2.0.1 it blocks for a full second (1000ms) every time.

This sketch will duplicate the error, no hardware required.

#include <Wire.h>

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

	Wire.begin();
}

void loop()
{

	uint32_t time_before=millis();

	const int address=10;
	const int length=16;

	int rcvd = Wire.requestFrom(address, (uint8_t) length, (uint8_t) true);
	if(rcvd==length)
	{
		uint8_t data[length];
		Wire.readBytes(data, length);
	}

	Serial.printf("I2C: Received %u bytes in %u ms\n",rcvd,millis()-time_before);

	delay(250);
}

If run on a regular ESP32 board with Arduino Core version 1.0.6, each Wire.requestFrom completes instantly or within 1 millisecond. With 2.0.1 it takes 1001 milliseconds.

I discovered the issue when recompiling a large project with the new Arduino core, so I stripped it down until I found the issue, but I don't know what's causing it.

I followed the code into esp32-hal-i2c.c and attempted to change the last parameter of i2c_master_cmd_begin to a hardcoded 1, and it still took a full second to complete the failed read -- the parameter change made no difference at all, so it seems perhaps the issue is all the way down inside the IDF?

Hardware:

Board: Generic 38-pin ESP32 dev board
Core Installation version: 2.0.1 (and for reference 1.0.6)
IDE name: Sloeber 4.4.0
Flash Frequency: 40Mhz
PSRAM enabled: no
Upload Speed: 921600
Computer OS: Windows 10

Debug Messages:

I tried, there are no I2C related debug messages even on Verbose.

[leifclaesson]

Thanks @me-no-dev

[CarlosGS]

Looks related to espressif/esp-idf#4999

[leifclaesson]

Looks related to espressif/esp-idf#4999

Now that you mention it yes, it does look similar.. but that thread is from April 2020 which is over a year ago. This was not a problem in 1.0.6 (as far as I could tell?) which is from March 2021 which is only 7 months ago at the time of this writing?

[CarlosGS]

Sorry I hadn't seen the dates. But since 1.0.6 is based on IDF v3.3.5 and that thread is about IDF v4.2, maybe the bug was introduced in between those IDF versions?

[leifclaesson]

Sorry I hadn't seen the dates. But since 1.0.6 is based on IDF v3.3.5 and that thread is about IDF v4.2, maybe the bug was introduced in between those IDF versions?

Definitely possible. :)

[leifclaesson]

Did you get a change to test it yet? The example code above requires no additional hardware to reproduce the issue.

[pgrawehr]

I can definitelly confirm the bug. When there's no device listening on the given address, Wire.requestFrom takes at least 1 second before it returns.

[simondddd]

Is there a simple workaround for this?
I have tried to recompile the libraries using https://github.com/espressif/esp32-arduino-lib-builder modifying the driver i2c.c as seen in espressif/esp-idf#4999 but I get errors when I use the libraries I obtain.