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I am trying to connect a PZEM004T (without display) to a USB port on my PC via a USB-TTL adapter board.

My intention is to send requests to the PZEM via the Adapter board. I had attempted by connecting the RX-TX cables in both ways (cross: RX to TX and vice versa, or ther direct, RX-RX and TX-TX). I also tried using both the 5V and 3V options to power the PZEM from the USB-TTL adapter (5V and 3.3V).

With a serial terminal programmer like the https://sites.google.com/site/terminalbpp/, I am sending the commands to the PZEM from my computer.

The observations are these:

  1. No response from the PZEM.
  2. 3.3V or 5.5V does not matter
  3. Direct or cross connection also did not matter.
  4. Replaced the cables but that neither worked.
  5. If I do a loopback (RX-TX short, the TTL adapter board works perfectly (echo back). So the TTL board seems ok per se.
  6. I did a loop back with the TTL connected to the PZEM as well. Now, this time, the serial responds with some junk. The RX/TX LED lamps on the board also light up. Until now, the TX lamp on the adapter was blinking (and the Power pin on the PZEM was glowing brighter) when sending data.

Can someone please help me with how to get the PZEM respond?

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I had worked previously with PZEM004T but I have never tried connecting it to PC with TTL. I'm not sure what you want to accomplish or this answer would help. Nevertheless, I would suggest using an Arduino with PZEM and view the measurements on Arduino's serial monitor.

I had used Oleg Sokolov's library for Arduino (works on ESP as well). https://platformio.org/lib/show/1662/PZEM004T Here is the circuit diagram:-

enter image description here

Connections are simple and the library works perfectly. This is the simplest way I've found.

Also, I came across this folder which contains details of interfacing PZEM to PC with USB-TTL. Although I have never tried it. You might find it useful.

http://www.mediafire.com/file/lk5wukg2v5n5iry/004T_software%252Bdriver%252Buser_manual.zip/file

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