roboglia.i2c.SharedI2CBus¶

class SharedI2CBus(**kwargs)[source]¶

Bases: roboglia.base.bus.SharedBus

An I2C bus that can be shared between threads in a multi-threaded environment.

It inherits all the initialization paramters from SharedBus and I2CBus.

__init__(**kwargs)[source]¶: Initialize self. See help(type(self)) for accurate signature.

__getattr__(name)¶: Forwards all unanswered calls to the main bus instance.

__repr__()¶: Invokes the main bus representation but changes the class name with the “Shared” class name to show a more accurate picture of the object.

can_use()¶

Tries to acquire the resource on behalf of the caller.

This method should be called every time a user of the bus wants to perform an operation. If the result is False the user does not have exclusive use of the bus and the actions are not guaranteed.

Warning

It is the responsibility of the user to call stop_using() as soon as possible after preforming the intended work with the bus if this method grants it access. Failing to do so will result in the bus being blocked by this user and prohibiting other users to access it.

Returns: True if managed to acquire the resource, False if not. It is the responsibility of the caller to decide what to do in case there is a False return including logging or Raising.
Return type: bool

naked_read(reg)¶

Calls the main bus read without invoking the lock. This is intended for those users that plan to use a series of read operations and they do not want to lock and release the bus every time, as this adds some overhead. Since the original bus’ read method is overridden (see below), any calls to read from a user will result in using the wrapped version defined in this class. Therefore in the scenario that the user wants to execute a series of quick reads the naked_read can be used as long as the user wraps the calls correctly for obtaining exclusive access:

if bus.can_use():
    val1 = bus.naked_read(reg1)
    val2 = bus.naked_read(reg2)
    val3 = bus.naked_read(reg3)
    ...
    bus.stop_using()
else:
    logger.warning('some warning')

Parameters: reg (BaseRegister or subclass) – The register object that needs to be read. Keep in mind that the register object also contains a reference to the device in the device attribute and it is up to the subclass to determine the way the information must be processed before providing it to the caller.
Returns: Typically it would return an int that will have to be handled by the caller.
Return type: int

naked_write(reg, value)¶

Calls the main bus write without invoking the lock. This is intended for those users that plan to use a series of write operations and they do not want to lock and release the bus every time, as this adds some overhead. Since the original bus’ write method is overridden (see below), any calls to write from a user will result in using the wrapped version defined in this class. Therefore in the scenario that the user wants to execute a series of quick writes the naked_write can be used as long as the user wraps the calls correctly for obtaining exclusive access:

if bus.can_use():
    val1 = bus.naked_write(reg1, val1)
    val2 = bus.naked_write(reg2, val2)
    val3 = bus.naked_write(reg3, val3)
    ...
    bus.stop_using()
else:
    logger.warning('some warning')

Parameters

reg (BaseRegister or subclass) – The register object that needs to be read. Keep in mind that the register object also contains a reference to the device in the device attribute and it is up to the subclass to determine the way the information must be processed before providing it to the caller.
value (int) – The value needed to the written to the device.

read(reg)¶

Overrides the main bus’ read() method and performs a safe read by wrapping the read call in a request to acquire the bus.

If the method is not able to acquire the bus in time (times out) it will log an error and return None.

Parameters: reg (BaseRegister or subclass) – The register object that needs to be read. Keep in mind that the register object also contains a reference to the device in the device attribute and it is up to the subclass to determine the way the information must be processed before providing it to the caller.
Returns: The value read for this register or None is the call failed to secure with bus within the timeout.
Return type: int

stop_using()¶: Releases the resource.

property timeout¶: Returns the timeout for requesting access to lock.

write(reg, value)¶

Overrides the main bus’ ~roboglia.base.BaseBus.write method and performs a safe write by wrapping the main bus write call in a request to acquire the bus.

If the method is not able to acquire the bus in time (times out) it will log an error.

Parameters

reg (BaseRegister or subclass) – The register object that needs to be read. Keep in mind that the register object also contains a reference to the device in the device attribute and it is up to the subclass to determine the way the information must be processed before providing it to the caller.
value (int) – The value to be written to the device.