Online Development Notebook > Index > ODN > USBm DLL Programming > Device Commands > StrobeWrite

StrobeWrite

Description:

This is a USBm.dll function that strobes the write of a byte value to a port. This command selects port A or B for the written byte, as well as a polarity (negative or positive) and a line (A.0 - B.7) to toggle. The byte is written and then the line toggled.

 

Command Syntax: (USBm.dll)

USBm_StrobeWrite(device, data, port, sel)

The USBm_StrobeWrite function syntax has these parts:

Part Description
device A zero-based index to address the appropriate USB device.
data Data to write.
port The port to write the byte. A value of 00h is port A, a value of 01h is port B.
sel The strobe direction and the strobe line selection.

 

Remarks:

Bit⁄Line Selection

Byte Value Result   Byte Value Result
00h Affect A.0   08h Affect B.0
01h Affect A.1   09h Affect B.1
02h Affect A.2   0Ah Affect B.2
03h Affect A.3   0Bh Affect B.3
04h Affect A.4   0Ch Affect B.4
05h Affect A.5   0Dh Affect B.5
06h Affect A.6   0Eh Affect B.6
07h Affect A.7   0Fh Affect B.7

 

With sel set to the Bit⁄Line Selection values, the strobe is negative-going. By adding 10h to this value, the strobe will be positive-going. For example: 18h would pulse B.0 from low to high, and back low.

 

VB Declaration

Public Declare Function USBm_StrobeWrite _
    Lib "USBm.dll" _
        (ByVal device As Byte, _
        ByVal data As Byte, _
        ByVal port As Byte, _
        ByVal sel As Byte) _
    As Integer

 

VB Example

USBm_SetBit 1, 15
USBm_StrobeWrite 1, &H55, 0, &H0F

If a device is connected to the U4xx that will accept a byte of data from port A when B.7 is toggled from high to low and back to high, then the above sample code would write &H55 to this device.

First set the B.7 line high with USBm_SetBit. The line is set high to begin with because the strobe functions do not initialize the state or direction of the line. (B.7 needs to be set as an output.)

Then write to port A and toggle B.7 low, then high. The breakdown of the first four bytes of the command is: 1 - device, &H55 - data to write, 0 - port to write (A), 15 - line to toggle (-F) and toggle direction (0-).

Changing to a positive strobe would necessitate changing the initial line value, and substituting &H1F for the fourth byte.

 

C Example

-TBD-

Hardware:  U401 USB Interface    U421 USB Interface
Programming:  USBm DLL Programming    Download Files
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