ESP8266 Community Forum

- Wed May 16, 2018 1:36 am #75941 I have an RFXtrx433 unit in my home automation system, this is a USB unit that communicates by serial at 38400 8N1.
I want this connected to my controller by Wifi, and have a few Wemos D1 mini boards laying around.

First i thought i'd just connect the USBs together and load ESPLink. No game, as the ESP didnt deliver power to the RFX.

I then tried to connect it at the 5V and RX/TX pins, and got som LED activity on the RFX, but no communication. After some fiddling around swapping RX/TX i got a few messages through, but no stable connection.

What am i doing wrong here? USB Serial levels are compatible with the RX/TX on the ESP right? Any other SW than ESPLink to try?

Any help is appreciated!

- Wed May 16, 2018 2:12 am #75942 First read about USB Host and USB Device ( https://en.wikipedia.org/wiki/USB section System design), and then think again about "Can I connect two USB DEVICES together?"...

- Wed May 16, 2018 2:33 am #75943 Yes, this dawned on me at the first attempt where nothing happened connecting them together.

The WEMOS does however have the regular TTL serial interface in addition to the USB port, and I (admittedly with limited knowledge) thought that could work, as the RFX seems to be a native Serial device requiring a serial driver on the connecting PC?

The RFX did start up and started reciveing 433 messages, so it doesnt seem to need any header info or similar on USB?

- Wed May 16, 2018 2:56 am #75944 Well, how do you know that RFX is native serial device? It's USB device, probably using CDC class. Don't even think about USB as a simple 3V3 TXD/RXD interface - read the specification first please before doing stupid things like connecting D+ / D- USB signals to RXD/TXD @ ESP8266...
Edit: According to this http://www.rfxcom.com/RFXtrx433E-USB-43 ... sceiver/en it contain FTDI so to get this to work you have to open RFX, search for TXD, RXD @ FTDI, solder wires to get signals out and cut FTDI TXD wire...