I recently found this model with the ID 'HW-0519' on it. It can be found online (HW-0519 in Aliexpress) and is sold for the purpose of converting UART to RS485 communication using Arduino devices. The MAX485 module (MAX485 in Banggood) is the more commonly used module for this purpose and has been used in many projects. The MAX485 has the following pins DI (data in), RO (receiver out), DE (Data Enable), RE (Receiver Enable), VCC, GND and the 'A' and 'B' pins for the RS485 device (Shown below).

enter image description here

The HW-0519 module, has a slightly different pin configuration, and I can't seem to wrap my head around it. It has Tx and Rx pins, which I am guessing match up with RO and DI respectively, but don't have enable pins. They have the VCC and GND pins along with the 'A' and 'B' pins, but also come with this pin marked in Chinese. I translated it using Google translate and it translates to something similar to 'Ground'. Which is not connected to the GND pin though (Shown below).

enter image description here

Does anyone know whether I can use the HW-0519 module in the same manner as the MAX485? If so, are there any libraries written for this module? I want to use the module for communication with a pH sensor like the one in this link.

  • 1
    Looks like the HW-0519 module implements automatic TX/RX mode switching for you.
    – Majenko
    Commented Apr 11, 2021 at 11:10
  • @Majenko does that mean I need not concern myself with controlling the direction of the data when writing the code with this HW-0519?
    – C Vith
    Commented Apr 13, 2021 at 10:02
  • @Majenko because, from what I understand, the DE and RE in the MAX485 module are usually connected together to one pin in the microcontroller and set to HIGH when transmitting and LOW when receiving.
    – C Vith
    Commented Apr 13, 2021 at 10:09
  • Theoretically, though there may be baud rate considerations to take into account and pre/post send delays or something. I don't know how the module works, so YMMV with it.
    – Majenko
    Commented Apr 13, 2021 at 10:13

2 Answers 2


I did a bit of research and found others who use this particular component for their RS485 communication purposes. It is difficult to get clear info because the device goes by different names and the most commonly used name is MAX485 (name of the IC), which is used interchangeably for both the components shown in the question.

It seems the more I search for the 'HW-0519', the more names I find for it. So far, it goes by the name 'MAX485', 'XY-017', and 'XY-K485'. A clear advantage for this 'HW-0519' is that it does not require D or R enabling, just straightforward Tx and Rx. It also has LEDs to show the data transfers. I found a project that used this module here. I am unsure about their pin connections from the ESP-32 though. It looks like they've connected the ESP-32's TX2 to the HW-0519's Tx, and the RX2 to the Rx. I thought it should be the other way around.

  • I confirm the module has to be connected like: Module TX--TX MCU and Module RX--RX MCU
    – dcasta
    Commented Oct 6, 2022 at 16:55

I have the HW-0519 (bought as https://www.amazon.co.uk/gp/product/B0BCFLTLGJ/ at £9.98 for 8x in 2023-09) and it matches the picture above quite closely enough. It is a variant, and the first difference I see is the (?) polyfuses JK075 above are T010 on mine.

I picked this because it has protection components on the board which others don't have - including the MAX485 board from Banggood linked above.

Both boards lack mounting holes but the MAX485 board has pins which (if they align?) might assist breadboard usage. For me, the prototyping phase will start with epoxying HW-0519 to a Lego brick.

I found a circuit diagram at https://easyeda.com/modules/HW-0519-TTL-to-RS485-converter_c4836920e8ec45b3924add8ac2acbe57 for something similar which helped me work out what's what. I'm not going to steal a copy and upload here but it looks like https://web.archive.org/web/*/https://image.easyeda.com/components/c4836920e8ec45b3924add8ac2acbe57.png .

My board is a cousin of the circuit diagram I found.

  • chips are named U2 (unmarked SOIC14, maybe 74HC04) and anon unmarked SOIC8,
  • its TVS protection is done as three chunky 2-pin diodes marked WK as in the HW-0519 above,
  • bus termination resistor is R9 and you have to short R0 to terminate the bus, so one at each end but not in the middle, in the usual way.
  • TVS protection comes to that third bus pin 球大(??) which I think is "earth big (something)"

Note that the bus ground is not connected to the logic ground GND on the 4-pin connector. You need to provide bus ground separately and maybe from a different source after considering fault currents.

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