I2c Class Reference

Detailed Description

An I2c object represents an i2c master and can talk multiple i2c slaves by selecting the correct address It is considered best practice to make sure the address is correct before doing any calls on i2c, in case another application or even thread changed the addres on that bus. Multiple instances of the same bus can exist.

    mraa::I2c i2c(I2C_BUS);

    i2c.address(HMC5883L_I2C_ADDR);
    rx_tx_buf[0] = HMC5883L_CONF_REG_B;
    rx_tx_buf[1] = GA_1_3_REG;
    i2c.write(rx_tx_buf, 2);

    i2c.address(HMC5883L_I2C_ADDR);
    rx_tx_buf[0] = HMC5883L_MODE_REG;
    rx_tx_buf[1] = HMC5883L_CONT_MODE;

    while (flag) {
        i2c.address(HMC5883L_I2C_ADDR);
        i2c.writeByte(HMC5883L_DATA_REG);

        i2c.address(HMC5883L_I2C_ADDR);
        i2c.read(rx_tx_buf, DATA_REG_SIZE);

        x = (rx_tx_buf[HMC5883L_X_MSB_REG] << 8) | rx_tx_buf[HMC5883L_X_LSB_REG];
        z = (rx_tx_buf[HMC5883L_Z_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Z_LSB_REG];
        y = (rx_tx_buf[HMC5883L_Y_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Y_LSB_REG];

        // scale and calculate direction
        direction = atan2(y * SCALE_0_92_MG, x * SCALE_0_92_MG);

        // check if the signs are reversed
        if (direction < 0)
            direction += 2 * M_PI;

        std::cout << "Compass scaled data x : %f, y : %f, z : %f" << x * SCALE_0_92_MG
                  << y * SCALE_0_92_MG << z * SCALE_0_92_MG << std::endl;
        std::cout << "Heading : %f" << direction * 180 / M_PI << std::endl;

        sleep(1);
    }

Public Member Functions
	I2c (int bus, bool raw=false)
	I2c (void *i2c_context)
	~I2c ()
Result	frequency (I2cMode mode)
Result	address (uint8_t address)
uint8_t	readByte ()
int	read (uint8_t *data, int length)
uint8_t	readReg (uint8_t reg)
uint16_t	readWordReg (uint8_t reg)
int	readBytesReg (uint8_t reg, uint8_t *data, int length)
Result	writeByte (uint8_t data)
Result	write (const uint8_t *data, int length)
Result	writeReg (uint8_t reg, uint8_t data)
Result	writeWordReg (uint8_t reg, uint16_t data)

Constructor & Destructor Documentation

I2c ( int  bus, bool  raw = false  )

inline

Instantiates an i2c bus. Multiple instances of the same bus can exist and the bus is not guaranteed to be on the correct address before read/write.

Parameters

bus	The i2c bus to use
raw	Whether to disable pinmapper for your board

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I2c ( void *  i2c_context )

inline

I2C constructor, takes a pointer to a I2C context and initialises the I2C class

Parameters

i2c_context

void * to an I2C context

~I2c ( )

inline

Closes the I2c Bus used. This does not guarantee the bus will not be usable by anyone else or communicates this disconnect to any slaves.

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Member Function Documentation

Result frequency ( I2cMode  mode )

inline

Sets the i2c Frequency for communication. Your board may not support the set frequency. Anyone can change this at any time and this will affect every slave on the bus

Parameters

mode	Frequency to set the bus to

Returns

Result of operation

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Result address ( uint8_t  address )

inline

Set the slave to talk to, typically called before every read/write operation

Parameters

address

Communicate to the i2c slave on this address

Returns

Result of operation

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uint8_t readByte ( )

inline

Read exactly one byte from the bus

Exceptions

std::invalid_argument

in case of error

Returns

char read from the bus

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int read ( uint8_t *  data, int  length  )

inline

Read length bytes from the bus into *data pointer

Parameters

data	Data to read into
length	Size of read in bytes to make

Returns

length of read, should match length

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uint8_t readReg ( uint8_t  reg )

inline

Read byte from an i2c register

Parameters

reg	Register to read from

Exceptions

std::invalid_argument

in case of error

Returns

char read from register

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uint16_t readWordReg ( uint8_t  reg )

inline

Read word from an i2c register

Parameters

reg	Register to read from

Exceptions

std::invalid_argument

in case of error

Returns

char read from register

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int readBytesReg ( uint8_t  reg, uint8_t *  data, int  length  )

inline

Read length bytes from the bus into *data pointer starting from an i2c register

Parameters

reg	Register to read from
data	pointer to the byte array to read data in to
length	max number of bytes to read

Returns

length passed to the function or -1

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Result writeByte ( uint8_t  data )

inline

Write a byte on the bus

Parameters

data	The byte to send on the bus

Returns

Result of operation

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Result write ( const uint8_t *  data, int  length  )

inline

Write length bytes to the bus, the first byte in the array is the command/register to write

Parameters

data	Buffer to send on the bus, first byte is i2c command
length	Size of buffer to send

Returns

Result of operation

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Result writeReg ( uint8_t  reg, uint8_t  data  )

inline

Write a byte to an i2c register

Parameters

reg	Register to write to
data	Value to write to register

Returns

Result of operation

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Result writeWordReg ( uint8_t  reg, uint16_t  data  )

inline

Write a word to an i2c register

Parameters

reg	Register to write to
data	Value to write to register

Returns

Result of operation

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The documentation for this class was generated from the following file:

• api/mraa/i2c.hpp