What is causing IMX7D's emmC SODIMM pin 32 to be at 1 V even if I configured it to output low voltage?

Technical Support
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1

Hello, guys how are you all?

I am facing an issue when trying to operate the SODIMM pin 32 (pin X16.29 on Iris 2.0). When I configure it as a general purpose output, the low voltage level stays at 1 V instead of 0 V yet the high level output is the correct correct 3.3 V. That being said, when I create a 1 kHz square signal with the pin, the high voltage is 3.3 V and the low voltage is 1 V - which can be seen via my scope.

My first guess was something related to the Iris board, so I checked the schematics and observed that SODDIM pin 32 is the UART_B_CTS signal, which is parallel-connected to the X16.29 pin and to the UART transceiver IC. Being UART_B_CTS an output pin of the transceiver (pin 16 of IC6), I thought that maybe the IC output was the cause of such behavior. I unsoldered that pin but had no success on observing a change in the operation scenario.

I also tried forcing a pull-down (via pad configuration in my code) to see if it would cause any type of different behavior but the earlier scenario was sustained.

That being said, my question is: is there anything connected in the Colibri SoM PCB that could cause such behavior? Could you guys please help?

Many thanks!

Fávero

HW and SW configuration:
Iris 2.0, Colibri IMX7D 1GB emmC
Embedded bare metal code being developed in the M4
Iris pin: X16.29; SODIMM pin: 32; functionality: general purpose output to generate a 1 kHz signal.

2

Hello, support!

Just to provide further information:
I am able to select the status of the X16.29 pin via Uboot using the gpio clear 181 and gpio set 181. When issuing a gpio clear 181, the output level stays at 1 V. When issuing a gpio set 181, the level goes to 3.3V. When using gpio clear 181 and gpio input 181, I can see via my scope that the voltage level is 1 V and Uboot reads that the voltage is high:

Colibri iMX7 # gpio clear 181
gpio: pin 181 (gpio 181) value is 0 // This voltage level is 1 V via scope
Colibri iMX7 # gpio input 181
gpio: pin 181 (gpio 181) value is 1 // But should not be.

Ps 1: I also tested the GPIO2_26, which is the Iris X16.14 pin. When issuing gpio sets, clears and inputs, everything works properly and signal measurement via scope is adequate.

Many thanks

Fávero

3

The X1.32 Colibri iMX7 pin routed directly to iMX7 ball E9 (SAI2_RXD). Nothing else is connected there on the module. Please check a pinmux settings at your M4 code.

4

Hello, Alex, thank you for your reply!
As I pointed in the update, even when issuing commands via Uboot the low level is 1 V - M4 is not even under operation.

Many thanks

5

So check a U_Boot pinmux settings.

6

Thank you, Alex!!