GPIO glitch during the bootup or power-on in IMX8M

[sunile]

I'm using a customized IMX8M board and using the GPIOs listed below.

1. GPIO BANK 3 -  GPIO 22

2. GPIO BANK 3 - GPIO 23

3. GPIO BANK 1 - GPIO 15

During the boot process, I observe  glitches on these gpio pins(where voltage raises nearly to 2v) and I can see  same behavior is  across all three gpios.

This behavior is seen with boot loader software and without any software running. I have attempted to configure these GPIO pins in u-boot-spl. However, the glitches occur much earlier in the boot process, within the first 5 milliseconds.

I have included measurements of the GPIOs with a 12V VCC supply. PFA. The GPIOs are represented in red, while the VCC is shown in yellow.

I couldn't get a clear idea whether the GPIO glitch happened because of the boot ROM code or with hardware. Any help would be appreciated.

Thanks in Advance.

[sunile]

Hi Chavira,

I'm using IMX8MM.
I have added the following code in the function "board_init_r" in the file common/spl/spl.c.

gpio_request(IMX_GPIO_NR(3, 22),"rGPIO");
gpio_direction_output(IMX_GPIO_NR(3, 22), 0);

When I added the above changes, I observed GPIO sets after 500ms. However, Our requirement is to set GPIO very early during boot up and resolve the glitch. Can you help me here how to set GPIOs very early in the boot stage?

I have attached the schematics of one GPIO connected to the relay.

Thanks & Regards 

Sunil

[Chavira]

Hi @sunile!

I think the problem is not the iMX8MM.

For Relay control I think is better an optocoupler instead of a transistor to maintain isolated the control of the power control.

Please remove the R70310 and do the measurement on P70329 again if the problem persists let me know!

Best Regards!

Chavira

[Chavira]

Hi @sunile!

Thank you for contacting NXP Support!

Do you refer to iMX8MM or iMX8MN?

Can you share the configuration of those pins?

Can you share your schematic to see how are connected those pins?

I recommend checking our evk and trying to connect in the same way to avoid the problems or following our Hardware design guide for iMX8M.

Best Regards!

Chavira