Colibri T20 SPI3 port not working

I’m using several Colibri T20 V1.2 modules with WEC7 image V2.3 and Toradex libraries V2.4.
I found a strange behavior while interfacing the SPI3 port.
In the application the SPI3 port is mapped to the pins:
CLK = 192
MOSI = 49
MISO = 51
CS0 = 53.
Sometimes, when the application starts, the MISO line of the module reads only 0xFF, but the MISO line on the PCB shows the correct data is transmitted from the device.
I first assumed there might be two pins configured as SPI3 MISO and one is pull-up, but the GPIOConfig tool shows only one pin at the MISO line.
During the tests it looks like there might be a temperature influence. If the Colibri module heats up, the propability of the issue during the software start increases.
I used the Update Tool to perform different startups. The problem appears only after a “coldstart”, and never when the system is running. It seems to disappear when the system is send through a “warmstart”.

Is this behavior known, and is there a workaround?

Could you please provide a source code of your test program?

Hi @5w3nC0 ,

The most logical explanation would be that there is a second MISO pin configured on another pin and that pin is floating. Maybe it’s not showing correctly in the GPIO Config Tool (or it’s named differently). The T20 has the feature to OR to inputs together if there are multiple configured instances on different pins.