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ESP32 and I2C CAL component Problem/Observation

Posted: Fri Nov 28, 2025 4:26 pm
by dvcam99
Hello FC Team,

today I made the follwing observation with my ESP32 and using I2C CAL component.

First of all the I2C CAL is only bringing data in Software mode on the I2C bus. Hardware mode either Ch1 or Ch2 will not bring any data on the bus. Unfortunately the clock rate is wrong in software mode with approx 400Hz.
Please see the follwing scope screen shoot.
esp32 lcd backpack 100khz i2c soft.png
esp32 lcd backpack 100khz i2c soft.png (164.68 KiB) Viewed 70 times
The I2C CAL component was set to 100Khz

If I use as a comparision LCD back pack I2C component I`ll get the correct clock rate.
Please see the next picture.
esp32 lcd backpack 100khz i2c.png
esp32 lcd backpack 100khz i2c.png (172.49 KiB) Viewed 70 times

So the question si what is wrong with I2C opperation at ESP32?

May somebody has dicovered a similar behaivior.

BR
Dirk

Re: ESP32 and I2C CAL component Problem/Observation

Posted: Fri Nov 28, 2025 4:32 pm
by mnfisher
Have used the i2c quite extensively in the past without issue - so unless a recent update has broken something?

Can you post your chart?

Martin

Re: ESP32 and I2C CAL component Problem/Observation

Posted: Fri Nov 28, 2025 6:03 pm
by dvcam99
Hi Martin,


fc file attached. In between I´ll checked I2C master component and I2C CAL component. Same result. Running only in software mode not hardware. Clock frequency approx 500Hz.
ESP_32_I2C_Test_1_0.fcfx
(8.55 KiB) Downloaded 5 times
BR

Dirk

Re: ESP32 and I2C CAL component Problem/Observation

Posted: Fri Nov 28, 2025 6:35 pm
by BenR
Hi Dirk,

I2c only works in transaction mode for esp32 hardware channels. Same for arm. I'll have a look at your program and see if I can transfer it to transaction mode for you.

Re: ESP32 and I2C CAL component Problem/Observation

Posted: Fri Nov 28, 2025 7:19 pm
by dvcam99
....transaction OK. Yes a example would be cool too.

In between I´ll checked the transaction hardware. Great it is working with the correct clock frequency.

Picture and FC file below:
esp32 lcd backpack 100khz i2c transaction.png
esp32 lcd backpack 100khz i2c transaction.png (156.44 KiB) Viewed 43 times
ESP_32_I2C_Test_1_0.fcfx
(8.91 KiB) Downloaded 4 times
BR

Dirk