Layer: Foundation · Build flags: PC_ENABLE_PN532, PC_ENABLE_GATEWAY

What this example teaches

An NFC/RFID reader plugged into the gateway - the ubiquitous NXP PN532 over I2C. Scanning a tag becomes a northbound event: the tag UID is enveloped and published.

tag scan --PN532/I2C--> pc_pn532_parse_frame() -> UID -> pc_gateway_uplink()
                                                       |
                                    envelope + topic  nfc/0/<target>
                                                       |
                                           northbound publish (MQTT/HTTP/WS)

The only hardware-specific code is the I2C carry of the frame bytes. The PN532 protocol - build a command, verify the 6-byte ACK, parse the response - is services/pn532:

uint8_t frame[32];
uint16_t n = pc_pn532_build_frame(PN532_TFI_HOST, cmd, cmd_len, frame, sizeof(frame));
// ... write frame over I2C, read back ...
if (pc_pn532_is_ack(ack, 6)) { /* command accepted */ }
uint8_t tfi; const uint8_t *pd; uint8_t pdlen;
if (pc_pn532_parse_frame(resp, r, &tfi, &pd, &pdlen) > 0) { /* pd = response PData */ }

Each frame is 00 00 FF | LEN | LCS | TFI | PData | DCS | 00 with a length checksum and a data checksum, both verified by the codec. This sketch runs GetFirmwareVersion at boot to confirm the chip, then polls InListPassiveTarget and bridges each detected tag's UID. The codec is host-tested against the documented command / response frames in test/test_pn532.

Wiring (ESP32 <-> PN532, I2C mode)

PN532	ESP32
SDA	GPIO 21
SCL	GPIO 22
VCC	3V3
GND	GND

Set the PN532's DIP switches to I2C. Its I2C address is 0x24.

Build-flag note

The flags must reach the library build, so pass them as build flags:

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPC_ENABLE_PN532=1 -DPC_ENABLE_GATEWAY=1" \
  --lib="." examples/Drivers/NfcGateway/NfcGateway.ino