You need just a basic voltmeter, you can probably borrow one.
Don't use one of the older "mechanical" ones with a needle and scale.
They won't hurt anything, but they load too much to be accurate on modern low-power electronics.
You can buy a DVM for $10. It will be poor quality and bring no joy to your heart but it will do the job.
Once you measure the TX pin vs GND you'll know what logic level you have.
I would guess that it's 3.3V, but it could be 1.8V.
You'll need a USB UART that works at that logic level.
If you want something upscale that works with either level you can buy this:
https://www.amazon.com/DSD-TECH-SH-U...dp/B07WX2DSVB/
Admittedly, adapters that only work on 3.3V can be found for ~$5.
Quote:
Originally Posted by pochopsp
What do you mean by "get a 1k resistor" ?
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Well, you can buy it. You can remove one from some junk electronics.
The value isn't critical, but 1k is a common value, 1000 ohms.
Ask an electronic friend to borrow one, its value is about $0.01
Unfortunately, nobody sells one for $0.01