roboglia.i2c.I2CBus

class I2CBus(name='I2CBUS', robot=None, port='', auto=True, mock=False, err=0.1)

Bases: roboglia.base.bus.BaseBus

Implements a communication bus for I2C devices.

I2CBus has the same paramters as BaseBus. Please refer to this class for the details of the parameters.

In addition there is an extra parameter mock.

At this moment the I2CBus supports devices with byte and word registers and permits defining composed regsiters with size > 1 that are treated as a single register.

Note

A gyroscope sensor might have registers for the z, y and z axes reading that are stored as pairs of registers like this:

gyro_x_l    #0x28
gyro_x_h    #0x29
gyro_y_l    #0x2A
gyro_y_h    #0x2B
gyro_z_l    #0x2C
gyro_z_h    #0x2D

For simplicity it is possible to define these registers like this in the device template:

registers:
    gyro_x:
        address: 0x28
        size: 2
    gyro_y:
        address: 0x2A
        size: 2
    gyro_z:
        address: 0x2C
        size: 2

By default the registers are Byte and the order of data is low-high as described in the :py:class:roboglia.base.`BaseRegister`. The bus will handle this by reading the two registers sequentially and computing the register’s value using the size of the register and the order.

Parameters

• name (str) – The name of the bus

• robot (BaseRobot) – A reference to the robot using the bus

• port (any) – An identification for the physical bus access. Some busses have string description like /dev/ttySC0 while others could be just integers (like in the case of I2C or SPI buses)

• auto (Bool) – If True the bus will be opened when the robot is started by calling BaseRobot.start(). If False the bus will be left closed during robot initialization and needs to be opened by the programmer.

• mock (bool) – Indicates if the I2C bus will use mock communication. It is provided for testing of functionality in CI environment. If True the bus will use the MockSMBus class for performing read and write operations.

• err (float) – For mock buses this parameter controls the probability of generating a random mock communication error.

__init__(name='I2CBUS', robot=None, port='', auto=True, mock=False, err=0.1)

Initialize self. See help(type(self)) for accurate signature.

open()

Opens the communication port.

close()

Closes the communication port, if the super().close() allows it. If the bus is used in any sync loops, the close request might fail.

property is_open

Returns True or False if the bus is open.

read(reg)

Depending on the size of the register is calls the corresponding function from the SMBus.

write(reg, value)

Depending on the size of the register it calls the corresponding write function from SMBus.

read_block(device, start_address, length)

Reads a block of registers of given length.

Parameters

• device (I2CDevice or subclass) – The device on the I2C bus

• start_addr (int) – The start address to read from

• length (int) – Number of bytes to read from the device

Returns

A list of bytes of length length with the values from the device. It intercepts any exceptions and logs them, in that case the return will be None.

Return type

list of int

write_block(device, start_address, data)

Writes a block of registers of given length.

Parameters

• device (I2CDevice or subclass) – The device on the I2C bus

• start_addr (int) – The start address to read from

• data (list of int) – The bytes to write to the device

Returns

It intercepts any exceptions and logs them.

Return type

None

__repr__()

Returns a representation of a BaseBus that includes the name of the class, the port and the status (open or closed).

property auto_open

Indicates if the bus should be opened by the robot when initializing.

property name

(read-only) the bus name.

property port

(read-only) the bus port.

property robot

The robot that owns the bus.