Issue by powering Rockpi 4 by GPIO : I2C unstable?

I am using armbian.
I am using I2C-7 and I connected a logic analyzer on both pin SCL and SDA (pins 3 & 5).
Here are two situations:
1/ Powering the Rockpi4 by USB (as usual):

  • I can notice the voltage remains high for both SCL and SDA while the ROCKPI is ON and perfectly working or Armbian: this is the normal situation.

2/ Powering the Rockpi by GPIO (pins 2,4,6,14)

  • I can notice sometime (it looks like randomly) the voltage become LOW for both SCL and SDA at the same time, for 500ns (then both signals become HIGH) while the ROCKPI is ON and perfectly working on Armbian. This is not normal as both pins SDA and SCL should stay HIGH and very stable. Consequently, I can’t use it.

The only difference between the two situation is the input power mode. Situation 1 is powered by USB and situation 2 is powered by GPIO.

Any idea???

I found the issue, my DC power was not well regulated…
It works fine with a Jetson Nano, maybe because this board is better controlled, the ROCKPI 4 is more sensible to voltage stability.
Anyway, changing the input power solve the issue.

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