Is RC522 13.56MHz RFID NFC Reader Compatible with Home Assistant (ESPHome)?
Electrical Specifications
Always confirm pin assignments against the manufacturer datasheet before wiring.
Compatibility Overview
RFID and NFC card access control scanner for smart door locks workshop tool authorization or personal keycard arming/disarming.
Wiring RC522 13.56MHz RFID NFC Reader to ESP32
| Module pin | ESP32 | Note |
|---|---|---|
| 3.3V | 3V3 | Not 5V. The MFRC522 has no regulator on this module and 5V destroys it. |
| GND | GND | |
| SDA (SS) | GPIO5 | Chip select, despite the silkscreen. cs_pin in the config. |
| SCK | GPIO18 | |
| MOSI | GPIO23 | |
| MISO | GPIO19 | |
| RST | unconnected | Optional. reset_pin: lets ESPHome hard-reset a reader that has wedged; worth wiring on a clone. |
| IRQ | unconnected |
Host pins are the ones the configuration on this page uses. Move a pin here and change it in the YAML — they are documented together so they cannot disagree.
Technical Specification Matrix
| Feature / Attribute | Specification / Status |
|---|---|
| Hardware Protocol | SPI Bus / 3.3V |
| Bridge Required | NO |
| Border Router Needed | None |
| Hardware Capabilities & Peripherals | Tag ID (HEX) NFC Card Scanner State Authorization Binary Note: these entities come from the ESPHome configuration you flash — each one needs its matching component in that YAML before it appears. |
| Pairing Complexity | Intermediate |
| Factory Reset Instruction | Hold BOOT button for 3s. |
Wire, Flash, Adopt, Check
Wire it up
Follow the wiring table above. The ESP32 pins there are the ones the configuration uses, so if you move one, change it in both places.
Flash the configuration
Create a new device in the ESPHome dashboard (the Home Assistant add-on) and paste the configuration below into it, or save it as emb_esp32_rc522_esphome.yaml and run esphome run emb_esp32_rc522_esphome.yaml. The first flash goes over USB. If it is not detected, hold BOOT button for 3s to put it in download mode. Every update after that is over the air.
Adopt it in Home Assistant
Settings → Devices & Services. A node on the same network shows up as a discovered ESPHome device within a minute of joining Wi-Fi; choose Configure and enter the API encryption key from your secrets.yaml. If discovery does not find it, add the ESPHome integration by hand with the node's IP address.
Check it works
The setup log reports the reader's firmware version, and a card on the antenna produces a tag_scanned event in Home Assistant's Tags page. A firmware version of 0x00 or 0xFF is SPI wiring, not the reader.
ESPHome Configuration
Starting configuration for RC522 13.56MHz RFID NFC Reader on ESP32. Untested on hardware — verify wiring and pins against your own board.
# ESPHome configuration for RC522 13.56MHz RFID NFC Reader
# Host: ESP32. Pin numbers below are host-side defaults — any free
# GPIO will do, and you should change them to match your own wiring.
esphome:
name: emb_esp32_rc522_esphome
friendly_name: "RC522 13.56MHz RFID NFC Reader"
esp32:
board: esp32dev
framework:
type: esp-idf
logger:
api:
encryption:
key: !secret api_encryption_key
ota:
- platform: esphome
password: !secret ota_password
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
spi:
clk_pin: GPIO18
mosi_pin: GPIO23
miso_pin: GPIO19
rc522_spi:
cs_pin: GPIO5
update_interval: 1s
on_tag:
then:
- homeassistant.tag_scanned: !lambda 'return x;'
Before you flash:
the !secret values come from your
secrets.yaml, and the GPIO numbers are host-side
defaults rather than properties of this part — change them to match how you actually wired it.
What Appears in Home Assistant
Each read fires tag_scanned in Home Assistant with the UID, the same as the PN532: tags appear under Settings → Tags and trigger automations.
Optional: binary_sensor: platform: rc522 with a uid: is on while that card is on the reader.
Known Problems and Fixes
SDA is not I2C here
The pin labelled SDA is the SPI chip select. Wiring it to the ESP32's I2C pins and adding an i2c: block is the most common way this reader ends up "not found". (There are boards rewired for I2C, and an rc522_i2c platform for them — but the stock blue module is SPI.)
Clones
Many of the cheap boards carry a clone of the MFRC522. The setup log prints the firmware version it reads back: 0x91 and 0x92 are the NXP silicon; other values are clones, some of which read fine and some of which miss cards or lock up. A reset_pin gives the component a way to recover the latter.
Short range, short wires
Two to three centimetres for a card, less for a keyfob. SPI does not like long cables either: keep the reader within about 20cm of the ESP32, and mount the antenna away from metal.
Not for phones, not for 125kHz
It reads MIFARE Classic and Ultralight UIDs and NTAG UIDs. Phones present randomised UIDs, so they cannot be enrolled reliably; 125kHz EM4100 fobs are a different frequency entirely.
Report a Pinout Error or Submit Tested Code Snippets
Found a pin mapping quirk or built a custom ESPHome YAML driver for RC522 13.56MHz RFID NFC Reader? Submit a pull request or report corrections to our index.