ACR122U

An ACR122U NFC reader

The ACR122U (also called just ACR122) is the most commonly available consumer grade USB NFC reader. Internally it uses a PN532 NFC chip, but this chip is not exposed directly to the host device so it cannot be used with other PN532 drivers. Its main method of communication is via a PCSC service, where it's usually plug and play. Its internal PCB is quite large with a fragile cable connection, which can make it difficult to incorporate in custom projects.

This reader is easily available on marketplace sites like Amazon, AliExpress, eBay and even from local smart card/security stores in your own country. It has a built in USB cable, an injection moulded case, internal speaker and external status LED (though compatibility of these varies between devices and platforms). It's fully compatible with NTAG and MIFARE Classic tags.

The ACR122U is no longer produced by its original designer ACS, so what you'll actually be buying is a hardware clone device. It's important to be aware that there can be differences internally between clones, which are impossible to tell without opening it up, and can affect compatibility with Zaparoo platforms. Some clones are incompatible with MiSTer and will likely never be supported, which is why the project no longer recommends them.

Overall, if you like the look and are willing to accept the risk of receiving an incompatible variant, it's a very solid performing NFC reader for a decent price.

MiSTer

An ACR122U on MiSTer is plug and play unless probe_device is disabled in the Core config file. It's normal for the LED on the reader to not light up and for it to make no noise when scanning a card. If your reader lights up or makes noise, it's a sign that it isn't compatible with MiSTer.

Core on MiSTer uses a special libnfc driver to speak with the reader. Using this driver means a PCSC daemon is not required to be running, which is not shipped with a standard MiSTer OS. The downside is this driver can be a bit picky and will fail for some reader variants as mentioned above. It may be possible in the future to build a PCSC daemon for MiSTer and ship a new PCSC driver so these readers will work, but there are currently no plans to do so and it's a significant piece of work.

Windows

The ACR122U should also be plug and play on the latest version of Windows. The reader's LED will light red and flash green when a card is scanned. The reader will also make a short beeping noise on scan.

Troubleshooting

If your reader isn't being detected properly, try checking the below steps are done:

Windows Device Manager example

Windows Services Manager example

• Enable the Smart Card Plug and Play service via regedit:

Description	Value
Registry Hive	HKEY_LOCAL_MACHINE
Registry Path	SOFTWARE\Policies\Microsoft\Windows\ScPnP
Value Name	EnableScPnP
Value Type	REG_DWORD
Enabled Value	1
Disabled Value	0

• Install the official ACS ACR122U driver. You can confirm it's working if "ACR122 Smart Card Reader" is shown in the "Smart card readers" section of the Device Manager.
• Make sure the "Smart Card" and "Smart Card Device Enumeration" services are both running with the startup type set to "Automatic" and "Automatic (Trigger Start)" respectively in the Services Manager.

All of these steps will require a reboot before they take effect. Thank you to spotUP for finding solutions to these issues.

Where To Buy

The ACR122U can be found by searching for "ACR122U" on sites like Amazon, eBay and AliExpress.

These are some known working listings submitted by users:

• Amazon (US) - Yosoo Store
• Amazon (US) - ACS Store
• Kogan (Australia)
• Everything ID (Australia)
• AliExpress (China) - 5YOA Official Store

Please be aware there's still a risk of receiving an incompatible variant even from these listings.