I'm using a NodeMCU, and a working code for reading Wiegand data, with this library.

I managed to successfully read the Wiegand signal from this device.

However, I also have this new AR-721H device, and I can't get the Wiegand to work. This is the manual for the device.

There is absolutely nothing coming to the mcu. Everything is wired identically as the working device.

According to the manual, everything should be working, but I am at a loss.

Can someone please tell me what I might be doing wrong?

The store clerk told me something about needing a controller that converts RS485 to RS232, but I have no idea what that means. I already made it work with another device...

1 Answer 1


It's quite cryptic from the little information in that (somewhat chaotic) "manual", but I interpret it that the Wiegand interface is an input port, not an output port. It is intended to connect that port to an external card reader or keypad as a remote interface (typically the other side of the door to this unit).

For communication with your Arduino you should use the RS-485 interface. For that you need an MAX485 breakout board.

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    RS485 is a specific electrical signalling format for UART (serial) data. You need to convert that to UART using a MAX485 - then you can feed it in to the TX/RX pins (or other pins using SoftwareSerial) and communicate using Serial. You'd need to know the baud rate and protocol though to make sense of the data.
    – Majenko
    Commented Jul 31, 2019 at 11:57
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    @Ivan Yes it does (or should have) - P3 is the RS-485 port.
    – Majenko
    Commented Jul 31, 2019 at 12:08
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    @Ivan I can tell you that it should be running at 9600 baud - but what the data content will be I haven't managed to discern.
    – Majenko
    Commented Jul 31, 2019 at 12:13
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    @Ivan Pay Dirt! kupdf.net/download/…
    – Majenko
    Commented Jul 31, 2019 at 12:15
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    You need a MAX485 breakout board. AR-721H <-> MAX485 <-> ESP8266. en.wikipedia.org/wiki/RS-485
    – Majenko
    Commented Jul 31, 2019 at 12:17

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