RS232 and RS485 RFID Readers with Serial Output

Start with the card or tag, then check that the reader has the port your host or controller expects.

If your host has only USB, use a USB-to-RS232 adapter or a keyboard-emulation reader. If you are wiring to an access controller, Wiegand is often simpler than serial; see access control and Wiegand readers and access control applications.

The settings below are as documented for each model. Before you write a parser, capture a few reads with a serial terminal on your evaluation sample and confirm the byte layout and checksum.

The 8-N-1 setting is documented for the 13.56 MHz models; for the 125 kHz models, check data bits and parity on the sample. Card numbers can be compared with the printed number using the card number converter and the card number formats guide.

• RS232 desktop readers: 1450 mm DB9 serial lead; L120-R, L150-R and H150-R also have a USB lead. They run on 5 V DC, so confirm how power will be supplied at your host in the quotation.
• Q420-M: red 12 V, black GND, green Wiegand DATA0, white Wiegand DATA1, brown RS485 A, orange RS485 B, blue RS232 RX, yellow RS232 TX. Supply 8–12 V DC, 800 mA.
• Q430-M: rear terminal block with RS485 (A, B), RS232 (RX, TX), Wiegand (DATA0, DATA1), TTL (RX, TX), GND and 12 V. Supply 8–12 V DC, 800 mA.
• A660-M: red DC+, black GND, white RS232 TX, grey RS485 B, purple RS485 A. The documented wiring has no RS232 RX line, so plan for one-way output from the reader. Confirm the supply voltage and Wiegand wiring for your build in the quotation.
• UHF integrated readers: 12 V DC supply and one trigger input for a vehicle loop or other sensor. Ask for the wiring diagram of your build (-M or -N) with the quotation.

General rules for bare-wire readers: connect reader TX to host RX (and reader RX to host TX where there is one), share a common ground, keep RS485 A and B consistent end to end (a swapped pair is a common fault), use shielded twisted pair on long RS485 runs, and never connect TTL pins to an RS232 port, because the voltage levels differ. See USB vs RS232 vs RS485 vs Wiegand and Wiegand reader wiring.

For the desktop readers, open the port at the documented settings, buffer bytes from STX (0x02) to ETX (0x03), validate the frame (the 13.56 MHz frame carries a BCC byte), then convert the ID to the format your database stores. Decide how your software treats the same card presented twice in a row, and log the raw hex while you commission the system; it shortens any later support call.

For the UHF integrated readers, set the output format, reading mode (continuous or triggered) and RF power with the test demo or through the SDK, then either parse the serial stream or build on the SDK. Use the trigger input when reads should happen only while a vehicle or object is present, so the reader does not report tags passing nearby. See Wiegand 26 vs 34, parking and vehicle access, and support for troubleshooting.