The arduino and ESP8266 EEPROM library only provides functions to read and write one byte at a time from the internal EEPROM. Note that EEPROM has limited number of writes.
In this tutorial I will provide some functions to store string to EEPROM and Read back to String variable. String is basically character array terminated with null (0x00).
Continue reading Arduino reading and writing string to EEPROM
In this tutorial we will learn How to interface Arduino UNO with RC522 RF ID Reader using Arduino library for MFRC522 and other RFID RC522 based modules.
This library read and write different types of Radio-Frequency IDentification (RFID) cards on your Arduino or NodeMCU using a RC522 based reader connected via the Serial Peripheral Interface (SPI) interface. Before we move to actual code lets know more about RF ID.
Question: Getting permission “error: cannot access /dev/ttyUSB0”
Answer: Just open terminal (Ctrl+Alt+T) and type this command and enter root password
$ sudo usermod -a -G dialout ${USER}
On Linux (Ubuntu), Arduino IDE will not be able to upload sketches (or communicate with the board at all) if you don’t change permissions on /dev/ttyUSB0 appropriately. Same as with the NodeMCU ESPlorer IDE, etc. Actually, this very problem comes up whenever you want to access a (virtual) Serial COM port on Linux.
It might happen that when you upload a sketch – after you have selected your board and serial port -, you get an error Error opening serial port … If you get this error, you need to set serial port permission.
Open Terminal and type:
$ ls -l /dev/ttyUSB*
you will get something like:
crw-rw---- 1 root dialout 188, 0 5 apr 23.01 ttyUSB0
The “0” at the end of USB might be a different number, or multiple entries might be returned. The data we need is “dialout” (is the group owner of the file).
Now we just need to add our user to the group:
$ sudo usermod -a -G dialout ${USER}
NOTE: where USER is NOT your linux user name keep as it is.
In some cases, You will need to log out and log in again for this change to take effect.
In this tutorial, we’ll learn how to program your NodeMCU or ESP8266 using an Arduino IDE. NodeMCU board is not available by default.
The NodeMCU ESP8266 is a low-cost WiFi module built by Espressif Systems. Its popularity has been growing among the hardware community thanks to its nice features and stability, to the point that it can be easily programmed using your Arduino IDE.
Note: Sometimes pakage_esp8266com_index.json link is down due to heavy download try again after few hours.
New version of Arduino supports String data type . In this tutorial we will see both integer to string and string to integer conversion. Conversion of integer to string can be done using single line statement.
Example 1: Integer to String Conversion Arduino
int a = 1234;
String myStr;
myStr = String(a); //Converts integer to string
Example 2: String to Integer conversion Arduino
String val = “1234”;
int result = val.toInt(); //Converts string to integer