Use GPIO1_IO4 for Wifi moulde PIN (WL_REG_ON)

[jim_huang]

Hi NXP experts,

Currently, I have found an issue about using MX6UL_PAD_GPIO1_IO04_GPIO1_IO04 as WL_REG_ON for wifi module.
I have configured this PINs as GPIO in my DTS, but after checking with SCOPE, I saw two kinds different behavior when DC ON Boot done. If this signal is generated by iMX6UL, how could I disable it?

One is as below. After Wifi init done successfully. I would see much noise in this boot result.
I don't know the noise come from, but I think it comes from iMX6UL.  
Does GPIO1_IO04 has the default behavior in BSP FW which doesn't mention in IMX6UL_14x14_evk.dts?

The other case is GPIO1_IO4 would be set as 2.8V after Wifi init done and the level would keep 2.8V.
At this moment, I bring up the wifi interface, it would be pulled up to 3.3V and has a chance to up successfully.
However, if I disable this interface once, it would be brought up anymore.
For the Wifi module, it might make sense due the WL_REG_ON is not at reset Level (0).
But, I also don't know why GPIO1_IO4 would keep 2.8V as the low-level stage.

Another found is the wave-form of Wifi driver init, the red is not Wifi driver make it.

Thanks,

Jim

[igorpadykov · Accepted solution]

Hi Jim

different behavior may be caused if, for example that pin is used by some other modules

(one can check dts file) or gpio direction (can be set in uboot/board/freescale/mx6ul_14x14_evk/mx6ul_14x14_evk.c) was not set as output and there is just keeper in input, causing different pin levels.

Best regards
igor
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