Which USB to serial chip?

Hi, I found there’s debug TTL pins on M2U. And I tried CH340 and CP2102 chip to convert serial to USB, but all failed. I connect M2U <-> chip, GND <-> GND, RX <-> TX, TX <-> RX. And set baud rate to 115200 in Putty or TeraTerm. With CH340, I got nothing on Putty or TeraTerm. With CP2102, I can get some readable output from TeraTerm or Putty, but most of them are unreadable codes (see [Picture 1], [Picture 2], [Picture 3]).

Maybe you guys can give me some advice or recommend me some other convert chip. Thanks

Update 20170103 I brought two new convert board, TL232 and PL2303, don’t help. But I found something interesting. When I connect USB to debug TTL while the board power is disconnected and RJ45 is connected, I can still getting output from COM port, although all the output is unreadable codes. Maybe the problem isn’t the adapter chip.

[Picture1] [Picture2] [Picture3]

I’am using PL2303 cable with 115200 baud…

The USB TTL to RS232 cable I’am using with success is this one: Link to Aliexpress PL2303TA

Maybe FT232 work well

Thanks for reply, I have similar cable, but I’m getting wired output from COM port, that’s really annoying me.

Thanks for your advice. Do you have the same problem getting wired output from COM port?