Coma FW-C2800 User's Guide download pdf (Page 211)

Data Pipe Manager (PIP Module)

Input/Output Overview and Pipes 6-7

There are no special format or data type requirements for the data to be

transferred by a pipe.

The online help in the Configuration Tool describes data pipe objects and

their parameters. See PIP Module in the TMS320 DSP/BIOS API Reference

Guide for your platform for information on the PIP module API.

6.3.1 Writing Data to a Pipe

The steps that a program should perform to write data to a pipe are as follows:

1) A function should first check the number of empty frames available to be

filled with data. To do this, the program must check the return value of

PIP_getWriterNumFrames. This function call returns the number of

empty frames in a pipe object.

2) If the number of empty frames is greater than 0, the function then calls

PIP_alloc to get an empty frame from the pipe.

3) Before returning from the PIP_alloc call, DSP/BIOS checks whether

there are additional empty frames available in the pipe. If so, the

notifyWriter function is called at this time.

4) Once PIP_alloc returns, the empty frame can be used by the application

code to store data. To do this the function needs to know the frame's start

address and its size. The API function PIP_getWriterAddr returns the

address of the beginning of the allocated frame. The API function

PIP_getWriterSize returns the number of words that can be written to the

frame. (The default value for an empty frame is the configured frame

size.)

5) When the frame is full of data, it can be returned to the pipe. If the number

of words written to the frame is less than the frame size, the function can

specify this by calling the PIP_setWriterSize function. Afterwards, call

PIP_put to return the data to the pipe.

6) Calling PIP_put causes the notifyReader function to run. This enables the

writer thread to notify the reader thread that there is data available in the

pipe to be read.

The code fragment in Figure 6-1 demonstrates how to write data to a pipe.

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Coma FW-C2800 User's Guide Page 211