Hi,
I'm working on a project with students and we've run into a bit of a snag. I have the Parallax 28140 successfully connected to an Arduino Uno and it reads the RFID cards and outputs them into the Serial Monitor just fine. I am trying to figure out how to get the code to discern a specific card, to determine if it's present or not.
My if/else statement at the bottom of the code simply does not work. It verifies just fine, but the onboard LED does not light up when the specific card is present.
One other note, the LED works fine. If I add a simple digitalWrite to turn it on, it does.
A last note: I got the 02007F318B from the Serial monitor. That's what the serial monitor displays when this particular card is read. I thought perhaps that was not what the Arduino "sees", so I added a zero thinking the null termination may be represented, but that didn't work either. Do I need to turn it back into ASCII like is earlier in the code?
Here's my code:
/*
Parallax RFID Reader: Basic Demonstration
Author: Joe Grand [www.grandideastudio.com]
Contact: support@parallax.com
Program Description:
This program provides a simple demonstration of the Parallax RFID Card
Reader (#28140). If a valid RFID tag is placed in front of the reader,
its unique ID is displayed in the Arduino Serial Monitor.
Please refer to the product manual for full details of system functionality
and capabilities.
Revisions:
1.0 (April 30, 2014): Initial release
*/
// include the SoftwareSerial library so we can use it to talk to the RFID Reader
#include <SoftwareSerial.h>
#define enablePin 9 // Connects to the RFID's ENABLE pin
#define rxPin 10 // Serial input (connects to the RFID's SOUT pin)
#define txPin 11 // Serial output (unused)
#define BUFSIZE 11 // Size of receive buffer (in bytes) (10-byte unique ID + null character)
#define RFID_START 0x0A // RFID Reader Start and Stop bytes
#define RFID_STOP 0x0D
// set up a new serial port
SoftwareSerial rfidSerial = SoftwareSerial(rxPin, txPin);
int ledPin = 13;
void setup() // Set up code called once on start-up
{
// define pin modes
pinMode(enablePin, OUTPUT);
pinMode(rxPin, INPUT);
pinMode(ledPin, OUTPUT);
digitalWrite(enablePin, HIGH); // disable RFID Reader
// setup Arduino Serial Monitor
Serial.begin(9600);
while (!Serial); // wait until ready
Serial.println("\n\nParallax RFID Card Reader");
// set the baud rate for the SoftwareSerial port
rfidSerial.begin(2400);
Serial.flush(); // wait for all bytes to be transmitted to the Serial Monitor
}
void loop() // Main code, to run repeatedly
{
/*
When the RFID Reader is active and a valid RFID tag is placed with range of the reader,
the tag's unique ID will be transmitted as a 12-byte printable ASCII string to the host
(start byte + ID + stop byte)
For example, for a tag with a valid ID of 0F0184F07A, the following bytes would be sent:
0x0A, 0x30, 0x46, 0x30, 0x31, 0x38, 0x34, 0x46, 0x30, 0x37, 0x41, 0x0D
We'll receive the ID and convert it to a null-terminated string with no start or stop byte.
*/
digitalWrite(enablePin, LOW); // enable the RFID Reader
// Wait for a response from the RFID Reader
// See Arduino readBytesUntil() as an alternative solution to read data from the reader
char rfidData[BUFSIZE]; // Buffer for incoming data
char offset = 0; // Offset into buffer
rfidData[0] = 0; // Clear the buffer
while(1)
{
if (rfidSerial.available() > 0) // If there are any bytes available to read, then the RFID Reader has probably seen a valid tag
{
rfidData[offset] = rfidSerial.read(); // Get the byte and store it in our buffer
if (rfidData[offset] == RFID_START) // If we receive the start byte from the RFID Reader, then get ready to receive the tag's unique ID
{
offset = -1; // Clear offset (will be incremented back to 0 at the end of the loop)
}
else if (rfidData[offset] == RFID_STOP) // If we receive the stop byte from the RFID Reader, then the tag's entire unique ID has been sent
{
rfidData[offset] = 0; // Null terminate the string of bytes we just received
break; // Break out of the loop
}
offset++; // Increment offset into array
if (offset >= BUFSIZE) offset = 0; // If the incoming data string is longer than our buffer, wrap around to avoid going out-of-bounds
}
if (rfidData == "02007F318B") {
digitalWrite(ledPin, HIGH); }
else {
digitalWrite(ledPin, LOW);
}
}
Serial.println(rfidData); // The rfidData string should now contain the tag's unique ID with a null termination, so display it on the Serial Monitor
Serial.flush(); // Wait for all bytes to be transmitted to the Serial Monitor
}
Your help is appreicated.
On behalf of my students,
Chris