Colibri VFxx X1 PIN 134 suitable for open drain

Hello everyone,

On a custom baseboard, a LED in open drain is connected to X1 #134 (GPIO only) .

After enable power source, the LED is illuminated at once, even if the IOMUXC_PTA17 is loaded with default values → 0x00000060. I can measure the voltage level on Pin 134 and it seems to be around 1.4V, that explains why the LED is on.

This doesn’t match my expectation of the pin behaviour. I would expect high impedance on this pin until IOMUXC_PTA17 is configured by software.

The VF61 and VF50 are showing the same issue.

Is the signal on PIN 134 only driven by the Vybrid GPIO?
Is there maybe a pullup/pulldown at this signal on Colibri PCB?

Best Regards,
Stefan Haase

Hello Stefan Haase,

For SODIMM_134, there is no external pull-up/pull-down used on the Colibri VFxx module.
SODIMM_134 is connected to Vybrid SoC “PAD_7” only as mentioned in the datasheet.

I did a quick check using GPIO config tool on Colibri Evaluation Board with Colibri VF50 (V1.1A) and VF61 (V1.1B) module running WinCE7.
GPIO (SODIMM_134) is working as expected (as GPIO output).
When configured as GPIO input, pin offers high impedance.

Are you share some more details about the software configuration used and your custom hardware.

Best Regards,
Satyan Raj