Pin +Direction Functions

Pins are used as inputs or outputs of binary signals. The Symbian platform +GPIO class does not support bidirectional pins. However, some platforms allow +pins to be in a quiescent state (also called floating or tri-stated). In this +case a pin can be in one of three logical states namely, True, False or quiescent +as specified in the enumeration TGpioDirection. The relevant +three-valued logic is specified in this table.

Implement the +pin direction functions

Implement SetPinDirection() for each value + of the enumeration TGpioDirection.
- Implement SetPinDirection() with + aDirection == EInput and return +value KErrNone.
  
  + Set the pin to behave as an input binary signal.
- Implement SetPinDirection() with + aDirection == EOutput and return +value KErrNone.
  
  + Set the pin to behave as an output binary signal.
- Implement SetPinDirection() with + aDirection == ETriStated and +return value KErrNone.
  
  + Set the pin to be in a quiescent state (also called floating or + deactivated).
  
  Only implement this +if the platform supports the quiescent state. The physical state +of the pin will be determined by the drive on the line. +
- Implement SetPinDirection() with return + value KErrNotSupported.
  
  + Return KErrNotSupported if the pin cannot + operate in the direction specified, for instance if ETriStated has +been passed and the platform does not support the quiescent state. +
Implement GetPinDirection() for each value + of the enumeration TGpioDirection.
- Implement GetPinDirection() with + aDirection containing EInput and +return value KErrNone.
  
  + Verify that the pin is behaving as a binary input signal. Set + aDirection to EInput +
- Implement GetPinDirection() with + aDirection containing EOutput and +return value KErrNone.
  
  + Verify that the pin is behaving as a binary output signal. Set + aDirection to EInput +
- Implement GetPinDirection() with + aDirection containing ETriStated and +return value KErrNone.
  
  + Verify that the pin is in the quiescent state. Set aDirection to ETriStated +
- Implement GetPinDirection() with return + value KErrNotSupported.
  
  + Return KErrNotSupported if reading the pin + direction is not supported.