#Arduino i2c example write register serial
#Arduino i2c example write register drivers
#Arduino i2c example write register code

To make things interesting and actually see the communication, I added a couple of LEDs and Potentiometers (one set for each UNO Board). In this demo, I connected two Arduino UNO boards to communicate over I2C Bus. To demonstrate the working of I2C in Arduino, let us build a small circuit. If you are using any other board then the following table will be useful to you as it describes the I2C pins on all the popular Arduino boards.ĪTmega328P Microcontroller used in Arduino UNO and Nano supports I2C Data Transfer speeds up to 400 kHz. In R3 of original Arduino UNO, there are two more pins near Digital IO Pin 13 (near the USB socket), dedicated to SDA and SCL. The A4 pin acts as SDA while the A5 pin acts as SCL. If you take a look at the pinout of Arduino UNO from the tutorial “ ARDUINO UNO PINOUT”, Analog Input pins A4 and A5 have an alternative function of I2C. I2C in ArduinoĪrduino supports I2C Communication. For more information on that, visit “ Basics of I2C Communication”.

I made an extensive tutorial on basics of I 2C Communication. Using this address, master selects a particular slave for data transmission (send or receive) and the selected slave responds according to request. Each slave device connected to the I2C bus has a unique 7-bit address. I2C network supports multiple masters and multiple slaves (but we usually see single master and multiple slaves). The clock signal is also supplied by the master. Bus Masters are responsible for sending and receiving data to and from the slave devices. There are two types of devices that connect to the I2C Bus: Master and Slave.

#Arduino i2c example write register drivers

Data is transmitted through the SDA line while the SCL line is used to synchronize the devices with the clock signal.īoth these bus lines are open-drain drivers and hence you have to use pull-up resistors to keep them HIGH.

#Arduino i2c example write register serial

The I2C Bus consists of two wires called the Serial Data (SDA) and the Serial Clock (SCL). This may not seem much but it is sufficient for interfacing sensors, memories and displays at small distances. Using I2C, you can transmit data at rates 100 kbit/s (clock 100 kHz – Standard Mode), 400 kbit/s (clock 400 kHz – Fast Mode), 1 Mbit/s (clock 1 MHz – Fast Mode Plus) and 3.4 Mbit/s (clock 3.4 MHz – High Speed Mode). Hence, it is sometimes also known as TWI (Two Wire Interface).

While the MPR121 IC already has several libraries for different platforms, other modules might not, so it becomes necessary to create them.I2C or I 2C is short for Inter-Integrated Circuit, a synchronous serial communication protocol developed by Phillips for communication between a fast Microcontroller and relatively slow peripherals (like Memory or Sensors) using just two wires. This allows you to pass different values with ease and take advantage of object-oriented programming paradigms, such as inheritance and passing objects to other functions.

#Arduino i2c example write register code

Code portability is very important when writing programs for various systems, which is why it makes sense to create and use your own library. _BV(pin_to_read) //The _BV(n) macro simply means to left-shift a 1 n-spaces left (1 << n) /* Here it is in binaryĠ0000000000000100 //This equates to true Make a Custom LibraryĪfter getting to know which registers perform which operations, it gets a little tedious to write many instructions just to get a single value in several places. Now, to see if a pin is active, take that pin’s value and use it to shift a 1 that many spaces to the left, then do a bit-wise & operation to combine them. For example, imagine pins 2, 7, and 11 were active reg0 would be 10000100, and reg1 would be 00001000.

Since reg1 is the MSB value, it needs to be bit-shifted 8 spaces to the left to allow for the LSB value, reg0, to be added on at the end. Uint16_t is the datatype for a number that is 2 bytes (hence the 16, which is the number of bits) and unsigned, which means it can only be positive, and it also means the first bit will not be treated as a sign flag. Then, combine them into a single unsigned int using: Read data from register 0x00 and 0x01, storing the 8-bit values into variables: To combine them into one larger value, the following operation is performed: This means that the data for the 12 pins is split between the two registers. The MPR121 stores pin states (0 or 1) in two bytes, with the LSB (Least Significant Bit) corresponding to either touch-pin 0 or touch-pin 8, since bytes have only 8 bits. For the MPR121, binary touch data is stored in registers 0x00 and 0x01.