LPC54618J512 GPIO Pin Initial State Issue

[nithin3200]

Hello everyone,

I have a custom PCB mounted with an LPC54618J512 controller. I have initially configured the GPIO pin (PIO4_16) as a digital output with an initial state set to low. This pin is used to switch an N-channel MOSFET.

During the booting period, the GPIO pin should remain low, but I am observing a 250 ms high pulse before it goes to the low state. I need the GPIO state to remain low throughout the booting period. This issue is not specific to any particular GPIO pin; it occurs across all GPIO pins. I am unsure why I am getting this 250 ms high pulse.

For reference, I am attaching the GPIO configuration screenshot. The yellow pulse represents the GPIO (PIO4_16) signals.

Any suggestions to resolve this issue would be greatly appreciated.

Thank you!

[xiangjun_rong]

Hi,

As you know that the GPIO pin is in input mode in default after Reset, so the pin is subject to noise.

Pls try to connect a pull-down resistor on the pin and check if the pulse appears or not after reset.

If the pulse still appears after you connect a pull-down resistor, it is a tough issue.

BR

Xiangjun Rong

[nithin3200]

Hi@ xiangjun_rong

Thanks for the reply. We have already connected the pull-down resistor in the hardware. Are there any other issues we should check?

BR

Nithin

[xiangjun_rong]

Hi,

Pls connect a 5K ohm pull-down resistor on the PIO4_16 pin. If you still see the high pulse during the start-up process, at this time, because the software has not begun to be executed, so software can not solve it. For hardware, the pull-down resistor is the only way I suppose.

As I said it is a tough issue.

BR

XiangJun Rong

[nithin3200 · Accepted solution]

@xiangjun_rong ,

Thanks for your prompt replay. As per your suggestion I connected the 5K ohm pull down resistor. The noise has been removed, and the issue is solved. 

Thank you very much for your guidance.

BR

Nithin