Various Serial to WiFi adapters, I need a suggestion for a best option

I have some small automation project whose elements are Arudinos connected using bluetooth modems to communication/command center (raspberry with simple control website). Number of items comes close to bt maximum and i have begun to search for alternatives, that may be able to use higher speeds for some later uses. I have found some new category of devices, the serial to wifi adapters. I have found some devices, but little to no reviews and experiences about using them, so I need help deciding before I buy some of those devices.

  1. USR USR-WIFI232-A, price ca. 26usd I have found documentation file ( about this product and was deeply impressed by all the options on paper.
  2. USR USR-WIFI232-T, price ca. 13usd This is low power version of first device. Maybe I have overlooked something, but I could not find why this device costs a half of the first one. It only misses the internal antenna chip.
  3. Hi-Link HLK-MO3, price ca. 11usd Could not find much about it
  4. Hi-Link HLK-RM04, price ca. 14usd Could not find much about it either
  5. TLG10UA03 FZ0417, price ca. 13.5usd I have found some content on youtube in Spanish or Portuguese language.
  6. 8devices Carambola 2, price ca. 19eur; with evaluation board 33eur

The device should be able to communicate in both directions, receiving by wifi sending serial and other way around. AP mode is not needed for all current and planned uses, because I will use a dedicated router for that network segment. Wifi security WPA2 is much needed, but as I can tell all of those devices have appropriate security level. I would like to be able to program device without any evaluation board (which as I understand is not possible with Carambola2).

Thankful in advance, SaleB

I have got one of these: USR USR-WIFI232-T I will keep you posted

jluu, does this wifi board work fine with the built libraries????

In this case, wich libraries do you use???

I´ve seen the Waveshare WIFI232 + WIFI 500 motherboard.... but I don´t know if someone has used it... I really need a Wifi conection.

Does anyone use the TP-link WIFI router (hacked with OPENWRT o without it)

Many thanks!!!

Hi guys,

I was wondering how you were getting on with your wifi modules.

I bought a UART Wifi module from Aliexpress for about $12, which has the model number TLN13UA03 on it.

There wasn't any documentation with it, but the board appears to be the same or similar to the Electhouse VSD03.

Strangely after I did a factory reset, the board wifi SSID changed from UARTwifi to. Wifi-socket, so I think the board is from a wifi controlled mains socket.

I have managed to do some basic stuff with it, including sending an email, and also displaying a basic web page. But some things don't work at all, and there are limitations that are annoying.

The web admin for the module is on http port 80' ie the same as normal web access, so although it has a separate user definable web server port e.g. 50000, you can't disable web web admin, so you always have to put the :50000 at the end of the URL.

Also some commands don't seem to work at all. E.g. Create an incoming server socket e.g. On port 8080 to act as a second web server. As this seems to stop the existing web server on 50000 and also doesn't accept any connections.

So basically I think you can only use the built in web server e.g. On 50000

It would be better if the admin was in another port e.g. 433 or 8080

Using the built in web server is also a bit problematic, as its not possible to terminate the connection to a client after the page has been sent,as required in The HTTP 1 standard. So all web page responses must send content-length, which makes the web page generation far more complex, as the length is sent in the header before the page http text.

So perhaps the ttl232 ones would be better as they are probably designed to be used for embedded micros and not use for a wifi socket

I have got one of these: USR USR-WIFI232-T
I will keep you posted

Here is the english documentation attached.

Best regards

USR-WIFI232-T.pdf (2.37 MB)

OK, I got it running:
bi-directional serial communication, one side is Serial1 a 115200 baud on the arduino Mega2560,
the other side is a telnet window opened talking on my home network to a local Wifi address implemented by the device.

I configured it as AP+STA through its internal web server (initially through its own AP at address, see documentation), no use of any other software or library.

The hardware connection is similar to this one:, with the exception that I connected to TX1/RX1 on the Mega (pins 18/19), notice the 3.3 V supply and the resistors acting as level shifters. The difficulty was adapting the 2mm pitch of the module to the common 0.1", but you only need 4 wires: (GND, 3.3V, TX,RX).

The test (character forwarding) software on the mega:
#include <serial.h>

void setup(){
Serial.println(“Hello Computer”);

void loop() {
// read from port 0, send to port 1:
if (Serial.available()) {
int inByte =;
// read from port 1, send to port 0:
if (Serial1.available()) {
int inByte =;

Did you get any farther with this?

I've been able to get serial talking to the module, but I'm not quite sure what to say.

IMHO these modules have now been superseded by the ESP8266 modules

The 8266 ones can be programmed to have either an AT command set or run Lua, or you can even upload your own C code to them.

I'd advise you get an ESP8266 device. There are loads of them comming out at the moment.

Look on ebay etc for esp8266, they come in various sizes, ie number of pins as they have their own GPIO as well as serial comms

I have some ESP 01 and ESP 03 modules and have some ESP 12 on order, but I now see some that use normal pins so can be plugged to a breadboard

Take your pick ;-)