topic Re: NXP RT1170 Output Voltage level in Parallel output in i.MX RT Crossover MCUs

NXP RT1170 Output Voltage level in Parallel output

abady1000 — Wed, 15 Oct 2025 08:17:18 GMT

I have a problem in a custom board, the is in voltage level in the clock generated from NXP RT1176 parallel interface !

I have manufactured a board based on chip NXP RT1170, I received the board and it worked well with me, and every thing seems fine.

I started developing on the MCU, I was able to receive BT656 video using CSI, I was able to use its parallel interface and stream video to micro display and I was able to use multiple different serial interfaces successfully.

I noticed random red dots appear on the display, they are very clear when the video is Black&White, I did a lot of investigation on this issue but couldn't find the cause. I checked all frame buffers inside RAM (SDR) but they all are fine!

I measured RGB parallel signals (when sending B&W, they all should be the same) and they seems identical, no differences in rising time or falling time, they all behave the same. I also changed the boards, wires, micro displays, but nothing changed.

One thing I noticed was the Parallel output clock was a little bit out of the level it should be on!

The clock frequency is correct, but voltage level is (-0.7V , 3.9V) instead of (0V, 3.3V)!

I am not sure if this is what causing the issue, but is this level correct?! (it is obviously not), what could cause the issue?

I checked all the input voltage to the system and their level is correct.

I ran the same application in the evaluation board EVKB-MIMXRT1170 and the level is good!

My chip exact number is "MIMXRT1176CVM8A" and the evaluations chip exact number is "MIMXRT1176DVMAA"

Re: NXP RT1170 Output Voltage level in Parallel output

mayliu1 — Thu, 16 Oct 2025 10:51:46 GMT

Hi @abady1000 ,

Thank you so much for your interest in our products and for using our community.

1：Please confirm that the IO bank used for the parallel interface is powered by 3.3V. Measure the voltage using an oscilloscope and provide screenshots of the relevant module schematic design. Have you compared the hardware design of your custom development board with that of the MIMXRT1170-EVKB?

2: Please confirm that the program running on the MIMXRT1170-EVKB development board without issues is completely identical to the program running on your custom development board.

3: Have you tried reducing the clock frequency to see if the occurrence of the anomaly decreases?

Best Regards
MayLiu

Re: NXP RT1170 Output Voltage level in Parallel output

abady1000 — Tue, 21 Oct 2025 07:09:29 GMT

Thank you @mayliu1 for your response.

1: I will return for this point once I prepare the measures for you.

2: Yes, it was exactly the same, I didn't change even a comment, I uploaded the same exact binary on both boards, I didn't even change the IOs.

3: I tried both increasing and decreasing the clock speed, and it seems that is irrelevant to the issue, nothing changed.
My original clock speed is (~37.5MHz), I tried both (~70.0 MHz) and (~15.0 MHz) and there were no change in the behavior of the clock.