How to set GPIO level when IM8MQ board is powered on

[Joe_C]

I now implement LOGO display on UBOOT on IMX8MQ board, but the backlight will light up after boot.The backlight is designed using a backlight control chip. The enabling foot of the backlight control chip can control the backlight to turn on and off.The current requirement is to power on the default pin output low level, but now we use GPIO1_3 default level is high level.I initialized the pins in the spl_board_init() function in spl.c, but it didn't work.What do I do to get the pin output low level as soon as the board is powered up.

[weidong_sun]

Hi,

The following are suggestions for you:
1. Please check your backlight circuit to see if there is a pull-up resistor, and pull the EN pin to a high level.
2. You can control GPIO in spl.c, and you can find the reference code in imx8mq_evk.c. However, this may not achieve your purpose, because the operation of spl.c also takes time.
3. When power on, the working state of the CPU pins
You can find the status of each pin in the datasheet. Some pins are PD 90K and some are PU 27K. If you want the backlight not to light up when power on, then you need to select the PD 90K pin.
4. Personal advice
In order to achieve your design purpose, you'd better have a 10K or 4.7K pull-down resistor in the circuit.

Have a nice day!

B.R

weidong