HiLetgo 5pcs TTL to RS485 485 to Serial UART Level Reciprocal Hardware Automatic Flow Control UART to RS485 Converter RS485 to TTL

I do a lot of Home Assistant builds and have used many different types of device. These RS485 controllers have auto flow control and are by far the easiest to get working, especially for novices to this protocol.

These RS485 modules are a major improvement over older models that require manual flow control. The automatic flow control works flawlessly, making them much easier to integrate into a project. As other reviewers have noted, wiring is straightforward: TX on your Arduino (or similar device) connects to TX on the module, and RX to RX. For the RS485 side, B- connects to B-, and A+ to A+. On the receiving unit, TX and RX follow the same mapping. I used the spare pair in an RJ11 twisted pair cable to carry VCC and GND between the modules, which worked perfectly. In the demo video, you can see a yellow LED flashing once per second—this is triggered across the RS485 link. There's also a built-in LED on the ItsyBitsy board flashing every five seconds, controlling a relay at the other end. The TX/RX LEDs on both modules flicker as data is sent and received, confirming everything is working as expected. I’m giving 4 stars instead of 5 because the physical design is awkward for use with solderless breadboards. The modules are so long that you need to place two standard breadboards side by side just to accommodate them once the headers are soldered. A shorter, more compact form factor would have been much more convenient.

I used this between a PZEM-017 and an ESP32 to monitor DC current/voltage. Worked as expected, but note that alot of the online references show TX to RX and RX to TX. I found that this RS485 adapter worked only with TX to TX and RX to RX. outside of that worked perfectly. I only wish it had external led pins for TX/RX led connections.

As a couple of other reviews point out, connect TX of this device to TX of microcontroller, and RX of this device to RX of microcontroller (that is a bit counter-intuitive compared to other devices I used) I like that it is auto-duplexing and can work with VCC of 3.3V or 5V. Soldering is required, and the boards don't come with any headers or terminal blocks. Very inexpensive (at the price I got it for) for a five unit package.

They just work, no additional programing.

Product seemed to transmit correctly but receive was sketchy and varied between units. I was using this for a MODBUS device that did not have its own flow control which may have contributed to the problem. My main concern was the fact that the issue was not consistent between testing different units (pack of five) yet was still there in some form. I purchased a different device from amazon, ANMBEST, which was cheaper and came in packs of 10. They require an extra pin(or two) to enable Tx and Rx but seem to be very stable. The specs say that it uses a 5v supply but I am using a Parallax propeller with 3.3v and it seems to work just fine.

Some better than others. Push it they get warm. Requires filter caps and some resistors to get the best out of it.

Don't let the lack of documentation scare you. I bought these to connect a Raspberry Pi Pico to a Zero over a long distance. This was easier than I feared. First enable UART on both devices, then connect Tx of one to Rx of the other and visa-versa. Once you get the communication working just insert these in the path: this time Tx and Rx of both devices to the Tx and Rx of these RS-485 units (Tx to Tx, Rx to Rx). Connect the RS-485 A to A, B to B, ground to ground. That's it, no programming needed, they just work.