Board doesn't boot when SDA pin is not in tri-state

Hardware MKR Family MKRGSM1400
1

Hi,

I used I2C feature to communicate with an other board (SDA, SDL, GND pins connected).

When power up the boards, I noticed that I have to force SDA, SDL pins from my other board in high impedance, otherwise the MKR board remains in an undefined state (program is not started, and CHRG led blinks quickly).

Let me know if you have the same be behaviour with your MKR board (you can simply connect SDL pin to GND)?

Is it an hardware bug?

2

Hi @alexduch,

There is a PMIC connected to the I2C ports of the board. When the board boots, the boot loader tries to put it to a "safe" configuration for charging.

3

Hi @sandeepmistry,

There is a PMIC connected to the I2C ports of the board. When the board boots, the boot loader tries to put it to a "safe" configuration for charging.

What is the good practise to use I2C without to be stuck in the "safe" configuration?
I put a delay on the second board (pins in tri-state) before the MKR boot is done but It is not really a "clean" solution.

Finally, I have configured an other I2C (on pin 0&1) and I don't have the problem with these pins.