IMX8MM GPIOs

[mikemalgin]

Hi,

I'm trying to use the pins that are being exposed at J1003 on iMX 8MM EVK on Android 9, specifically, 

UART3_RXD (gpio5.IO[26]) 
UART3_TXD(gpio5.IO[27]) 

SAI5_RXD3(gpio3.IO[24])

SAI5_RXD2(gpio3.IO[22])

Few questions: 

1. Since they are being exposed, can I safely assume that they are not used by any other component?

2. I tried to "export" them, however, when measuring the voltage when toggling from HI to LO it doesn't seem to work correctly(the value changes from 0 to 1, but the multimeter shows 3.3v in both states).

3. Do I have to define them in the evk's dts file? Defining them as below; is it the correct way?

pinctrl_hog: hoggrp {
fsl,pins = <

MX8MM_IOMUXC_UART3_TXD_GPIO5_IO27 0x19
MX8MM_IOMUXC_UART3_RXD_GPIO5_IO26 0x19
MX8MM_IOMUXC_SAI5_RXD3_GPIO3_IO24 0x19
MX8MM_IOMUXC_SAI5_RXD2_GPIO3_IO23 0x19
>;
};

Any help will be appreciated.

Thanks.

[igorpadykov]

Hi mike

one can look at i.MX8MM dts file and check how gpios are used;

linux/arch/arm64/boot/dts/freescale/fsl-imx8mm-evk.dts

fsl-imx8mm-evk.dts\freescale\dts\boot\arm64\arch - linux-imx - i.MX Linux kernel 

Best regards
igor
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[mikemalgin]

Hi Igor, 

Thanks, I checked the dts(see below) it looks like UART3_RXD/TXD as well SAI5_RXD3/2 are both taken? Is this correct?

 (UART3 is used for SPI and SAI5 used for mic)

Why NXP is making it so hard to use their EVK board? There isn't even a single GPIO(except the ECSPI2 which I use for spidev) on J1003 that is available and can be easily used on Android... 

Am I missing something here?

[sreedhar_appala]

Hi MikeMalgin,

Are you able to figure out anyway to use GPIO pin on i.MX8MM evk hw?

Could you please let me know if you are able to.

Thank you, Sreedhar