Online Development Notebook > Index > Programming Overview > Device Commands > DirectionA (and variations)

DirectionA (and variations) - Set direction of port A

Description:

This is a function that sets the i⁄o direction of port A.

Command Syntax: (USBm.dll)

USBm_DirectionA( device, dir0, dir1 )

The USBm_DirectionA function syntax has these parts:

Part Description
device A zero-based index to address the appropriate USB device.
dir0 Port direction.
dir1 Port direction.

 

USBm_DirectionAOut(device)

The USBm_DirectionAOut function syntax has these parts:

Part Description
device A zero-based index to address the appropriate USB device.

 

USBm_DirectionAIn(device)

The USBm_DirectionAIn function syntax has these parts:

Part Description
device A zero-based index to address the appropriate USB device.

 

USBm_DirectionAInPullup(device)

The USBm_DirectionAInPullup function syntax has these parts:

Part Description
device A zero-based index to address the appropriate USB device.

Remarks:

The individual pins of the ports can be set to input, or output. Input is set when both bits associated with a particular line are set to 0. There are different types of outputs available for the board, but generally setting both of the direction bits to 1 will suffice.

To set all pins in the port to input, set dir0 = 00h and dir1 = 00h. To set the highest port pin to output set the highest bit in both registers, dir0 = 80h and dir1 = 80h.

USBm_DirectionAOut will set all of the lines of port A to outputs.

USBm_DirectionAIn will set all of the lines of port A to inputs.

USBm_DirectionAInPullup will set all of the lines of port A to inputs with the internal pull up resistors enabled.

USBm_DirectionA is in all versions of the DLL. The variations are present in version 65 or newer.

VB Declaration

Public Declare Function USBm_DirectionA _
    Lib "USBm.dll" _
        (ByVal device As Byte, _
        ByVal dir0 As Byte, _
        ByVal dir1 As Byte) _
    As Integer

Public Declare Function USBm_DirectionAOut _
    Lib "USBm.dll" _
        (ByVal device As Byte) _
   As Integer

Public Declare Function USBm_DirectionAIn _
    Lib "USBm.dll" _
        (ByVal device As Byte) _
    As Integer

Public Declare Function USBm_DirectionAInPullup _
    Lib "USBm.dll" _
        (ByVal device As Byte) _
    As Integer

VB Example

USBm_DirectionA 1, 0, 0

This code fragment sets port A of device 1 to input.

C Prototype

int USBm_DirectionA( unsigned char device, unsigned char dir0, unsigned char dir1 );
int USBm_DirectionAOut( unsigned char device );
int USBm_DirectionAIn( unsigned char device );
int USBm_DirectionAInPullup( unsigned char device );

C Example

USBm_DirectionAInPullup( 0 );

This code fragment sets port A of device 0 to input, with the internal pull up resistors enabled.

RobotBASIC

usbm_DirectionA(ne_DeviceNumber,ne_PinsDirection,ne_PinsFormat)

Returns true if successful, false otherwise. This function sets the direction of each specific pin in the port. A 1 in the pin position means output, a 0 is input. The format byte should contain a 1 for each pin's position if it is output. If it is input you can have a 1 if you want an input pin with a pull up resistor, a 0 if you want the pin to have no pull up resistor.

Raw Command  Format:

Byte Number Description
0 09h: DirectionACmd
1 direction0 The most significant bit of the byte value is associated with A.7
2 direction1 The most significant bit of the byte value is associated with A.7
3 <not used>
4 <not used>
5 <not used>
6 <not used>
7 <not used>

Raw Command  Format Details:

Byte 0 contains the command. Byte 1 is written to the direction0 control register, byte 2 is written to the direction1 control register appropriate for this port. Byte 3 through byte 7 are unused.

The individual pins of the ports can be set to input, or output. Input is set when both bits associated with a particular line are set to 0. There are different types of outputs available for the board, but generally setting both of the direction bits to 1 will suffice.

Raw Command Response Format:

Byte Number Description
0 09h: DirectionACmd
1 <not used>
2 <not used>
3 <not used>
4 <not used>
5 <not used>
6 <not used>
7 <not used>

Raw Command Response Format Details:

Byte 0 contains the command. Byte 1 through byte 7 are unused.

Raw Command Example Usage:

The command 09-00-00-00-00-00-00-00 will set the port to all input, the command 09-FF-FF-00-00-00-00-00 will set the port to all output. To have the upper nibble be input and the lower nibble output, use the command 09-0F-0F-00-00-00-00-00.

Hardware:  U401 USB Interface    U421 USB Interface   U451 USB Interface

Programming:  USBm DLL Programming    Download Files

Application Notes:  U4x1 Application Notes    Misc Applications and Information    FAQ

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