Exit status 1 expected primary-expression before ']' Arduino

Question

Here's the whole error:

 Arduino: 1.6.7 (Windows 7), Board: "Arduino/Genuino Uno"
 *\readMifare\readMifare.ino: In function 'void loop()':
 readMifare:113: error: expected primary-expression before ']' token
 if (uid[] == { 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 }) {
 ^
 readMifare:113: error: expected primary-expression before '{' token
 if (uid[] == { 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 }) {
 ^
 readMifare:113: error: expected ')' before '{' token
 readMifare:121: error: expected '}' at end of input
 }
 ^
 exit status 1
 expected primary-expression before ']' token
 This report would have more information with
 "Show verbose output during compilation"
 enabled in File > Preferences.

Here's the code

 #include <Wire.h>
 #include <SPI.h>
 #include <Adafruit_PN532.h>
 // If using the breakout with SPI, define the pins for SPI communication.
 #define PN532_SCK (2)
 #define PN532_MOSI (3)
 #define PN532_SS (4)
 #define PN532_MISO (5)
 // If using the breakout or shield with I2C, define just the pins connected
 // to the IRQ and reset lines. Use the values below (2, 3) for the shield!
 #define PN532_IRQ (2)
 #define PN532_RESET (3) // Not connected by default on the NFC Shield
 // Uncomment just _one_ line below depending on how your breakout or shield
 // is connected to the Arduino:
 // Use this line for a breakout with a software SPI connection (recommended):
 Adafruit_PN532 nfc(PN532_SCK, PN532_MISO, PN532_MOSI, PN532_SS);
 // Use this line for a breakout with a hardware SPI connection. Note that
 // the PN532 SCK, MOSI, and MISO pins need to be connected to the Arduino's
 // hardware SPI SCK, MOSI, and MISO pins. On an Arduino Uno these are
 // SCK = 13, MOSI = 11, MISO = 12. The SS line can be any digital IO pin.
 //Adafruit_PN532 nfc(PN532_SS);
 // Or use this line for a breakout or shield with an I2C connection:
 //Adafruit_PN532 nfc(PN532_IRQ, PN532_RESET);
 #if defined(ARDUINO_ARCH_SAMD)
 // for Zero, output on USB Serial console, remove line below if using programming port to program the Zero!
 // also change #define in Adafruit_PN532.cpp library file
 #define Serial SerialUSB
 #endif
 #include <Servo.h>
 Servo servo1;
 void setup(void) {
 #ifndef ESP8266
 while (!Serial); // for Leonardo/Micro/Zero
 #endif
 Serial.begin(115200);
 Serial.println("Hello!");
 nfc.begin();
 uint32_t versiondata = nfc.getFirmwareVersion();
 if (! versiondata) {
 Serial.print("Didn't find PN53x board");
 while (1); // halt
 }
 // Got ok data, print it out!
 Serial.print("Found chip PN5"); Serial.println((versiondata>>24) & 0xFF, HEX); 
 Serial.print("Firmware ver. "); Serial.print((versiondata>>16) & 0xFF, DEC); 
 Serial.print('.'); Serial.println((versiondata>>8) & 0xFF, DEC);
 // configure board to read RFID tags
 nfc.SAMConfig();
 Serial.println("Waiting for an ISO14443A Card ...");
 servo1.attach(9); 
 }
 void loop(void) {
 uint8_t success;
 uint8_t uid[] = { 0, 0, 0, 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, &uidLength);
 if (uid[] = { 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 }) {
 int position;
 for(position = 0; position < 180; position += 2){
 servo1.write(position);
 delay(20);
 }
 }

Please note that I'm using an example from the Adafruit official PN532 library examples and trying to edit it.

• Dave X: You probably do not want an '=' in the if statement. What example had this?
• Dahacker305: This is what I added, still new though, so what should I input?
• Gerben: To compare you use ==. = is for assignment. Common mistake, even by the professionals.

Answer 1

I wouldn't use strncmp because the UID might have zeroes in it. This looks safer:

 uint8_t uid[] = { 0, 0, 0, 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)
 const uint8_t wantedUid [] = { 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 };
 // 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, &uidLength);
 if (success && 
 uidLength == sizeof (wantedUid) &&
 memcmp (uid, wantedUid, sizeof wantedUid) == 0) {
 ...

I threw in a test for the uidLength being the expected size, otherwise you might find a 4-byte card happens to match the first four bytes of the wanted UID.

memcmp compares a block of memory for the number of bytes you specify. It returns zero on a match.

Answer 2

You probably need something like:

uint8_t uidTarget[] = { 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 };
...
if (success && !strncmp((const char*) uidTarget,(const char*)uidSource,8)) {

Your '=' tries to do an assignment, and an '==' would check if the pointers to the arrays are identical, rather than the contents of the arrays. strncmp() tests equality of strings of characters, and the (const char*) casts the uint8_t values as characters.

Nick Gammon's answer is better.

• Dahacker305: added what you told me to add, error: readMifare:113: error: invalid conversion from 'uint8_t* {aka unsigned char*}' to 'const char*' [-fpermissive] if (success && !strncmp(uid,{ 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 },8)) { readMifare:113: error: cannot convert '<brace-enclosed initializer list>' to 'const char*' for argument '2' to 'int strncmp(const char*, const char*, size_t)' readMifare:121: error: expected '}' at end of input } exit status 1 invalid conversion from 'uint8_t* {aka unsigned char*}' to 'const char*' [-fpermissive]
• Edgar Bonet: @Dahacker305: remove the const.
• Mikael Patel: "if (success && !strncmp(uid,{ 0x04, 0xEC, 0x89, 0x32, 0x55, 0x42, 0x80 },8))" - no you cannot do that. The ID must be an array variable.