TTL level of TFMini dropping to ~1.2V when connecting to THS1


I have a TFMini Plus LiDAR. Until now I’ve been using it with a UART<>USB converter on the Jetson Nano USB and it has been working great.

Now I want to connect the UART wires directly to the UART port on /dev/ttyTHS1.

After hours of debugging I discovered with an oscilloscope that when I plug the Tx pin of the TFMini to pin 10 on the Jetson (Rx of THS1), the logic level of the TFMini drops from 3.3V to around 1.2V, which is probably why the Jetson isn’t picking up the signal.

This doesn’t happen when I connect the Tx pin to the Rx of the USB converter: The signal remains at 3.3V.

Why is this happening?

Hi avi22,

Are you using the devkit or custom board for Jetson Nano?
What’s your Jetpack version in use?

Could you share the block diagram of your connection?
How do you power your TFMini at this moment?

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