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S32K142 I2c sometimes doesn't work after Wakeup

Question asked by Tobias Hensle on May 22, 2019
Latest reply on May 27, 2019 by Victor Jimenez



I have a a problem with I2c bus on a S32K142 (PE RTM 2.0) that sometimes after wakeup from deep sleep the bus doesn't work. Neither the SCL nor SDA line will be pulled to GND, no start condition is generated.

The µC is the master and the bus runs at 200kHz and has two slave devices (Elmos BAP sensors), 5V supply.


I implemented a timeout routine which reset the I2c hardware, this includes the slaves. The 5V supply of the sensors and for the I2c is switched off and on again (sleep current reduction). The time between switch on and start of communication is 10ms.

The reset rountine is often called several times because after every reset a new timeout occurs and the procedure start from the beginning, because the I2c communication hasn't started.

At one point the communication will start again and everything works perfect but up to this point it takes often more than hundreds of milliseconds.


I hope this wasn't that much confusing and someone can help with that issue.


In the picture you can see the I2c lines SCL (yellow) and SDA (green) and a trigger during HW reset (orange). After 1.3s the communication works a ecpected.