SHT21 I2C unable to read

[kyjak]

I'm trying to get to work the Sensirion SHT21 I2C sensor on ESP32 without luck.
Using pins 21,22 as wire interface.
I tried all libraries I could find for SHT2x.
On arduino uno the code works, ESP does not.
It reads wrong sensor data = bogus.
It might be connected to the hal i2c library of esp32.
Do not have oscilloscope to show log :(

[architmuchhal12]

I am having the same issue #462 with the ADXL345 sensor. Works well with ESP8266 but fails to initialize I2C with ESP32.

[kyjak]

I did solve it partially by using this library https://github.com/markbeee/SHT21/tree/master/examples/SHT21_Demo
however, that does not answer, why we cannot use ANY library, I still see an I2C issue with esp's.
Something is wrong probably with the timings.

[me-no-dev]

It's not timings, it's something with the slaves themselves. ESP32's I2C bus is way more complex than the one found in AVR arduinos, so something somewhere is going wrong ;)
So I tested with 8 slaves on the I2C bus and all but one responded every time. That one was the SHT21.

[architmuchhal12]

I have switched to SPI communication for time being and it is working okay. I am using just one slave (ADXL345) and still, it does not respond.
So, is there a solution to counter ESP32's I2C @me-no-dev ?

[kyjak]

Hmm, even if I have only 1 sensor, so it's not a slave?

[stonie08]

Are you using the SHT21 in the "hold master mode"? I'm not using the arduino core, but on my ESP32 I get a correct reading from the SHT21 if I'm using the "no-hold-master" mode.
So for me the ESP32 ignores that the SHT21 is holding down the SCL line to force it into a wait state.

[stickbreaker]

@kyjak @architmuchhal12 @stonie08 I have posted a fix for the I2C subsystem that may be at the root of your problems, See #839 .

@stonie08 The ESP32's I2C subsytem enforces a bit TIMEOUT, at maximum it is around 12ms or 2^20 cpu clocks @ 80mhz. How long is the hold period during this conversion? If it is anywhere near 5ms the ESP32 will react badly.

Chuck.

[kyjak]

Thanks, will try out And let you know ;) Kyjak Get Outlook for Android<https://aka.ms/ghei36>

…

________________________________ From: chuck todd <notifications@github.com> Sent: Friday, November 17, 2017 12:41:22 AM To: espressif/arduino-esp32 Cc: mito; Mention Subject: Re: [espressif/arduino-esp32] SHT21 I2C unable to read (#464) @kyjak<https://github.com/kyjak> @architmuchhal12<https://github.com/architmuchhal12> @stonie08<https://github.com/stonie08> I have posted a fix for the I2C subsystem that may be at the root of your problems, See #839<#839> . @stonie08<https://github.com/stonie08> The ESP32's I2C subsytem enforces a bit TIMEOUT, at maximum it is around 12ms or 2^20 cpu clocks @ 80mhz. How long is the hold period during this conversion? If it is anywhere near 5ms the ESP32 will react badly. Chuck. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#464 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AOmdqloMa4BybeT8B8hfOzJ0WSwtFV6Kks5s3MgigaJpZM4OESKr>.

[electroZ-microsystems]

Thank you stickbreaker, I installed you version of arduio-esp32 and I can read my SHT21, it was almost not working with espressif.

[stickbreaker]

@manymany-many your welcome.

Chuck.

[copercini]

The I2C core was changed to @stickbreaker code officially after 13dcfe5 (thanks @stickbreaker), Let's close issues with old code and if have problems with the new code, open new issues =)