dipakgmx/atmega_twi

A C++ implementation of TWI communication for ATMega

ATMega TWI(I2C) interrupt based library

A C++ implementation of TWI communication of the ATmega640/1280/2560.
Master and slave communication is possible.

How to use:

Modify the CMakeLists.txt file:

Set the flash option:

Setting this to YES flashes the generated .hex file into the micro-controller

SET(FLASH YES)

Set the baud rate for flashing:

SET(BAUD 115200)

Set the programmer for flashing:

The default Arduino programmer was used in the CMakeLists.txt.

SET(PROGRAMMER wiring) 

Select the correct port for flashing:

set(PORT /dev/ttyACM0)

Building:

Run the following within the extracted folder.

mkdir Build
cd Build
cmake ..
make

Generated files would be found in the bin folder within the parent folder. If SET(FLASH ???) was set as YES, as explained earlier, the file is flashed onto the ATMega2560

Using the library:

Typical usage

• Calling the constructor:

  TWI twi;
  

• To set I2C mode as slave:

  twi.TWISetMode(TWIMode::Slave, 0x01);
  

  Here, 0x01 is the slave address.
• To set I2C mode as master:

  twi.TWISetMode(TWIMode::Master);
  

• To read or recieve use Read() function- depends on Master or slave:

  twi.Read();
  

• To transmit use Write() function- depends on Master or slave:

  twi.Write();
  

Functions used:

Function to set the transmission mode - Master or Slave

void TWI::TWISetMode(TWIMode requestedMode, 
                     uint8_t setSlaveAddress, 
                     PrescalerValue value, 
                     uint32_t twiFrequency)

• requestedMode Sets the transmission mode. Default mode is set to Master. For master - TWIMode::Master, for slave - TWIMode::Slave
• setSlaveAddress Sets the address when slave mode is selected. Default value is set to 0x01.
• value Sets the prescaler value. Default prescaler of 1 (prescaling to 0). Use
  PRESCALE_VALUE_1
PRESCALE_VALUE_4
PRESCALE_VALUE_16
PRESCALE_VALUE_64
• twiFrequency Sets the TWI communication frequency. Default value of 100000 (100 kHz)

Master transmitter function to write data into the TWI bus

void TWI::Write(uint8_t slaveAddress,
                const uint8_t *data,
                uint8_t dataLen,
                bool repeatedStart,
                bool TWIReadRequest)

• slaveAddress Address of the TWI slave device (7 bit wide)
• data Data to be transmitted. Sent in as an array
• dataLen Length of the data to be transmitted
• repeatedStart Boolean value, set as default to false. To be set to true if a repeated start is needed
• TWIReadRequest Boolean value, set as default to false. This value is used by the Read function only!

Overload of Write - Master transmitter function to write data into the TWI bus

Function is used to send char array to the Write function. This is necessary since the length of the character array is determined here.

void TWI::Write(const uint8_t slaveAddress,
                const char *const data,
                const bool repeatedStart)

• slaveAddress Address of the TWI slave device (7 bit wide)
• data char array to be transmitted
• repeatedStart Boolean value, set as default to false. To be set to true if a repeated start is needed

Slave transmitter function to write data into the TWI bus when requested by master

void TWI::Write(const char *const data)

• data Data to be transferred

Function to read data in Master Receiver mode

void TWI::Read(const uint8_t slaveAddress,
               uint8_t *data,
               uint8_t readBytesLen,
               const bool repeatedStart)

• slaveAddress Address of the TWI slave device
• data pointer to the array where the data shall be saved to
• readBytesLen Number of bytes the received data shall be
• repeatedStart Boolean value, set as default to false. To be set to true if a repeated start is needed

Overload of Read - Slave transmitter function to write data into the TWI bus

void TWI::Read()