Bare with me. I’m not very good at writing in Arduino/C.
I am reading and writing to an RFID tag using MFRC522.h
I can currently read the UID of a card and dump it to “UIDChar”
The UID of a card typically is 8 characters.
UID Example: 467EE9A9
I can use the mfrc522.MIFARE_SetUid function to write this UID to a new card. In order to do this I have to set the newUID to:
0x46,0x7E,0xE9,0xA9
I have written this into my code.
What I am wanting to do is convert the UID string into a byte array so that I can use that in place of my manually written 0x46,0x7E,0xE9,0xA9.
I use the convert function to convert the UID into that format.
It can that be displayed with “buf”.
Serial.println(buf);
Now my problem. If I replace the
byte newUid = {0x46,0x7E,0xE9,0xA9f};
with
byte newUid = {buf};
I get the error
invalid conversion from ‘char*’ to ‘byte {aka unsigned char}’
How can I set my “newUid” as “buf”?
// Creates a Wifi AP, Displays Website, and Reads RFID Tags
#define SS_PIN 0 //D2
#define RST_PIN 2 //D1
#include <SPI.h>
#include <MFRC522.h>
/* For RFID */
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance.
char buf[40]; // For string to byte array convertor
void convert(char *s)
{
int i, j, k;
buf[0] = 0x0;
for (j = 0, i = 0, k = 0; j < strlen(s); j++)
{
if (i++ == 0) {
buf[k++] = '0';
buf[k++] = 'x';
}
buf[k++] = s[j];
if (i == 2) {
if(j != strlen(s) -1) buf[k++] = ',';
i = 0;
}
}
buf[k] = 0x0;
}
void clone() {
/* RFID Read */
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent())
{
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial())
{
return;
}
//Show UID on serial monitor
Serial.println();
Serial.print(" UID tag :");
// Very basic UID dump
unsigned int hex_num;
hex_num = mfrc522.uid.uidByte[0] << 24;
hex_num += mfrc522.uid.uidByte[1] << 16;
hex_num += mfrc522.uid.uidByte[2] << 8;
hex_num += mfrc522.uid.uidByte[3];
// Get UID
int NFC_id = (int)hex_num;
Serial.print(NFC_id, HEX);
// Convert UID to string using an int and a base (hexadecimal)
String stringUID = String(NFC_id, HEX);
char UIDChar[10];
stringUID.toCharArray(UIDChar,10);
delay(1000);
Serial.println();
// Convert to uppercase
for (int i = 0; i < strlen(UIDChar); i++ )
{
if ( UIDChar[i] == NULL ) break;
UIDChar[i] = toupper(UIDChar[i]);
}
//Serial.print( &UIDChar[0] );
Serial.println();
convert(UIDChar);
Serial.println(buf);
/* RFID Write */
// Set new UID
// Change your UID hex string to 4 byte array
// I get error if I use byte newUid[] = {buf};
/* ERROR HERE */
byte newUid[] = {0x46,0x7E,0xE9,0xA9};
if ( mfrc522.MIFARE_SetUid(newUid, (byte)4, true) ) {
Serial.println( "Wrote new UID to card." );
}
// Halt PICC and re-select it so DumpToSerial doesn't get confused
mfrc522.PICC_HaltA();
if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
return;
}
// Dump the new memory contents
Serial.println( "New UID and contents:" );
mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
}
void setup() {
Serial.begin ( 115200 );
/* RFID */
SPI.begin(); // Initiate SPI bus
mfrc522.PCD_Init(); // Initiate MFRC522
clone();
}
void loop() {
}