readme.txt

一个ccs开发环境下的滤波器程序

Simple FIR filter on the C5402 DSK.		05/06/2002

Most of the examples coming with the C5402 DSK are written
using the DSK Board Library (dsk5402.lib and drv5402.lib).
This library is supplied in binary format only and doesn't 
follow the rules and the conventions of the Chip Support Library (CSL).

The CSL is now the preferred way to program the C5000 DSP peripherals, 
and is included in Code Composer Studio.
The original DSK Board Library is not documented and supported 
at the same level of the CSL,  so sometimes the user doesn't have
the complete control of the DSP.

Those 2 projects, derived from the Reference Framework #1, show how to create 
a simple loopback/audio filter application on the C5402 DSK using the CSL.
All the XDAIS interface has been stripped out, leaving only a small basic 
framework that should be easy to understand for the first time users.
In the DSP/BIOS project a Hardware Interrupt (HWI) is used so synchronize 
the processing, instead of the 2 pipes, again for simplicity; pipes give a higher level 
of abstraction and are very useful, but require more time to be properly understood. 
The idea here was to keep it simple.

The structure of the code is simple and self documenting:
2 DMA channels are set in ABU mode and use two ping-pong buffers 
(inBuffer and outBuffer) to read and send data from/to the audio codec.
The DMA ABU mode is a kind of auto-init mode, so the user doesn't need 
to restart the DMA at the end of each tranfer; the only limitation is 
that the 2 buffers must be properly aligned in memory 
(see the linker command file and the Users'Guide
SPRU302 TMS320C54x DSP Reference Set, Volume 5: Enhanced Peripherals page 3-23)

The DMA ch4 Interrupt Service Routine calles the audioProcess function 
(or posts the Audio SWI in the DSP/BIOS version), that performs the real audio processing.

In this example the user can select between 4 different types of FIR filters, 
by changing the value of the filterType variable or the status of the DIP SWITCHES 7 and 8:

Dip SW7		Dip SW8		FilterType

ON			ON				0			All pass
ON			OFF				1			Low Pass
OFF			ON				2			High Pass
OFF			OFF				3			Band Pass

The FIR filter is implemented using the C5400 DSPLIB, included in CCS.
All the code runs in the C5402 internal memory.

The audioProcess function can be easily changed to implement any other kind of algorithm.

The code can also be programmed in the DSK Boot Flash for stand-alone operation, 
using the FlashBurn CCS plugin and the files of the Flash subdirectory. 
FlashBurn is available as CCS free upgrade for regitered users, using Update Advisor
(help -> CCS on the Web -> Update Advisor). 

The complete Reference Frameworks are available on http://www.dspvillage.com/.