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12. Input Devices

Group assignment

In this week’s group assignment, we tried to probe an input device‚Äôs analog and digital signals.

Individual assignment

In this week’s individual assignment, I connected a RFID reader to the board I designed for my final project. And tested it with a Mifare 1k RFID card. The RFID reader I choosed is PN532 module, a tiny size reader that is suitable to install under the Fab Kart, my Final Project.

Spec Details
Supported Protocal I2C, SPI, HSU (High Speed UART)
Supported RFID Cards Mifare 1k, 4k, Ultralight, and DesFire cards
Max. Reading Distance 5cm~7cm
Size 43*40mm

Protocal Selection

The PN532 supports three type of protocals: High Speed UART(HSU), I2C and SPI. I can select the desired protocal by changing the combinations of the DIP switch on board:

Protocal 1 2
HSU 0 0
I2C 1 0
SPI 0 1

I choosed I2C as commnuication protocal, it uses only two signal pins and I could add more input/output I2C sensors/devices to the same pins without connecting extra signal pin.


I wrote a program to test the PN532 module. To visualize the result, I also added a WS2812 LED strip, which can control each diode’s color and brightness on it.

//RFID Settings
#include <Wire.h>
#include <PN532_I2C.h>
#include <PN532.h>
#include <NfcAdapter.h>
PN532_I2C pn532i2c(Wire);
PN532 nfc(pn532i2c);
uint8_t uid_SpeedBoost[] = {0x33, 0x9D, 0xB9, 0x12};
bool boostTriggered = false;

//WS2812 Strip Settings
#include "Freenove_WS2812_Lib_for_ESP32.h"
#define LEDS_PIN  12
#define CHANNEL   0
#define normal 0
#define start 1
#define rainbow 2
Freenove_ESP32_WS2812 strip = Freenove_ESP32_WS2812(8, LEDS_PIN, CHANNEL, TYPE_GRB);

void setup(void) {

void loop(void) {
  boolean success;
  uint8_t uid[] = { 0, 0, 0, 0};  // Buffer to store the returned UID
  uint8_t uidLength;                        // Length of the UID (4 or 7 bytes depending on ISO14443A card type)

  // Wait for an ISO14443A type cards (Mifare, etc.).  When one is found
  // 'uid' will be populated with the UID, and uidLength will indicate
  // if the uid is 4 bytes (Mifare Classic) or 7 bytes (Mifare Ultralight)
  success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, &uid[0], &uidLength);

  if (success) {
    Serial.println("Found a card!");
    Serial.print("UID Length: "); Serial.print(uidLength, DEC); Serial.println(" bytes");
    Serial.print("UID Value: ");
    for (uint8_t i = 0; i < uidLength; i++)
      Serial.print(" 0x"); Serial.print(uid[i], HEX);

    if ((uid[0] == uid_SpeedBoost[0]) && (uid[1] == uid_SpeedBoost[1]) && (uid[2] == uid_SpeedBoost[2]) && (uid[3] == uid_SpeedBoost[3])) {
      boostTriggered = true;
      Serial.println("Speed Boost!");
    // Wait 1 second before continuing


References & Files Download

PN532 Test Program PN532 Library NDEF Library

Last update: June 28, 2022