Hi,
Pls very new to all these;
I am reading and writing a value to serial com output; wherein buffer2 is a byte
Serial.write(buffer2[1]);
For example, I read a value of "3" on the serial com output, however I want to display this value on a 16x2 LCD but I am getting weird characters.
I would like to print this value to the LCD and also use the value as an integer.
Any help will be highly appreciated,
Thanls
In C/C++, the start index of an array is 0.
olamuse:
Any help will be highly appreciated,
Post your complete program.
Have a look at the examples in Serial Input Basics - simple reliable ways to receive data.
...R
Basically, this code is the modification of the an example "rfid read personal info" in the MFRC522 library. I am reading an integer/float stored on RFID tag. I am really concerned/I want to manipulate the value retrieved value stored in the RFID.
#include <SPI.h>
#include <MFRC522.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
constexpr uint8_t RST_PIN = 9; // Configurable, see typical pin layout above
constexpr uint8_t SS_PIN = 10; // Configurable, see typical pin layout above
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance
#define BACKLIGHT_PIN 13
#define SS_PIN 10
#define RST_PIN 9
#define SP_PIN 8
#define LED_GREEN A0
#define LED_RED A1
const int Btn = A2;
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
//*****************************************************************************************//
void setup() {
Serial.begin(9600); // Initialize serial communications with the PC
SPI.begin(); // Init SPI bus
mfrc522.PCD_Init(); // Init MFRC522 card
Serial.println(F("Read personal data on a MIFARE PICC:")); //shows in serial that it is ready to read
lcd.begin(16,2); // initialize the lcd
lcd.clear (); // go home
}
//*****************************************************************************************//
void loop() {
// Prepare key - all keys are set to FFFFFFFFFFFFh at chip delivery from the factory.
MFRC522::MIFARE_Key key;
for (byte i = 0; i < 6; i++) key.keyByte[i] = 0xFF;
//some variables we need
byte block;
byte len;
MFRC522::StatusCode status;
//-------------------------------------------
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent()) {
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial()) {
return;
}
Serial.println(F("**Card Detected:**"));
//-------------------------------------------
mfrc522.PICC_DumpDetailsToSerial(&(mfrc522.uid)); //dump some details about the card
//mfrc522.PICC_DumpToSerial(&(mfrc522.uid)); //uncomment this to see all blocks in hex
//-------------------------------------------
Serial.print(F("Name: "));
byte buffer1[18];
block = 4;
len = 18;
//------------------------------------------- GET FIRST NAME
lcd.clear();
status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, 4, &key, &(mfrc522.uid)); //line 834 of MFRC522.cpp file
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Authentication failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
status = mfrc522.MIFARE_Read(block, buffer1, &len);
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Reading failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
lcd.setCursor(0, 0);
//PRINT FIRST NAME
for (uint8_t i = 0; i < 16; i++)
{
if (buffer1[i] != 32)
{
Serial.write(buffer1[i]);
lcd.write((buffer1[i]));
}
}
Serial.print(" ");
//---------------------------------------- GET LAST NAME
byte buffer2[18];
block = 1;
status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, 1, &key, &(mfrc522.uid)); //line 834
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Authentication failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
status = mfrc522.MIFARE_Read(block, buffer2, &len);
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Reading failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
lcd.setCursor(0, 1);
//PRINT VALUE
for (uint8_t i = 0; i < 16; i++) {
Serial.write(buffer2[i]);
lcd.write((buffer2[i]));
}
//----------------------------------------
Serial.println(F("\n**End Reading**\n"));
delay(1000); //change value if you want to read cards faster
mfrc522.PICC_HaltA();
mfrc522.PCD_StopCrypto1();
}
//*****************************************************************************************//
Why don't people read this before posting a programming question ?
olamuse:
Basically, this code is the modification of ...
Where in that program is the part you want help with?
...R
//PRINT VALUE
for (uint8_t i = 0; i < 16; i++) {
Serial.write(buffer2[i]);
lcd.write((buffer2[i]));
}
I want to be able to manipulate the value retrieved from RFID
I want to be able to manipulate the value retrieved from RFID
What do you want to do with it ?
I want the buffer value (I pre-stored the buffer value in the memory location of the RFID) as an integer so that I can add it (the retrieved value) to itself over a period time and then display total value.
olamuse:
I want the buffer value (I pre-stored the buffer value in the memory location of the RFID) as an integer so that I can add it (the retrieved value) to itself over a period time and then display total value.
OK. You are writing 16 values to the LCD and the screen. What do you see ?
Thanks, you probing has helped me realize the problem.
I was only storing the last value that was retrieved from the buffer. I kept writing over the values as they were being retrieved and displayed on the LCD.
So instead of having for example character 326 to convert to an integer to use, I have character 6 converted to an integer for use.
Big Brain Fart
instead of having for example character 326
I still don't understand what you are trying to do but whatever it is 326 is not a character. It could be a number of characters in an array, each in a different position (array induces 0, 1 and 2). If you inserted a zero into the next position then you would have a C style string and could easily convert it to an integer using the atoi() function.