520099584ee_14| Application Note
Engineer To Engineer Note
EE-14
Notes on using Analog Devices' DSP, audio, & video components from the Computer Products Division Phone: (800) ANALOG-D or (781) 461-3881, FAX: (781) 461-3010, EMAIL: dsp.support@analog.com
C Programs on the ADSP-2181 EZKIT LITE
Last Modified: 5/6/96
switches. And finally 2181.ACH is an architecture file that can be used with the EZ-LITE. For more information on C coding with the Analog Devices' DSPs refer to the C tools manual, the ADDS21XX-SW-PC release note. 1) Extensions to the ANSI C compiler The Analog Devices GNU based C compiler conforms to the ANSI C standard. However, there are additions or extensions to the ANSI C language that are specific to the ADSP processors. The instruction: volatile int left_in, right_in; is an example of an extension to the int data type. Using volatile will force the DSP to place the variables left_in and right_in into memory locations -- as opposed to manipulating the data in registers only. Another extension to ANSI C is the PM data type. Using the data type: int pm coeff[10]; will create a buffer in the DSP's program memory for storing coefficients. Without the pm extension all data will be placed in data memory. 2) Accessing memory-mapped registers in C The DSP reserves a section of internal memory for configurati
on registers. Configuring the serial ports, internal timer, IDMA, BDMA, memory wait states, etc. is accomplished by writing to these memory mapped registers. To accomplish this in C, use a #define command to create a label or pointer for the memory location. In our CTIP35.C program we're initializing the wait states for the IO memory space using: #define DM_Wait_Reg *(int *) 0x3ffe. Then in the code, you can write to that memory location using: DM_Wait_Reg=0x0fff;
This DSP EZ-Note explains in detail a basic ADSP-2100 family C program. This C routine provides a simple shell for use with the ADDS-21XX-EZ-LITE. The EZ-LITE is the low-cost ADSP-2181 based evaluation board. While the EZ-LITE comes with software, it does not include the C compiler. So this EZ-Note assumes that you have the complete version of the Analog Devices software (ADDS21XX-SW-PC). The current version of the software is release 5.1. Our main C program is CTIP35.C. As you can see from the listing, individual lines have been numbered. The lines are explained in the corresponding sections below. CTIP35.C when run on the EZ-LITE takes the input from the AD1847 stereo codec called LEFT_IN and RIGHT_IN and loops it back to the 1847 by writing to LEFT_OUT and RIGHT_OUT. You can add on to this simple talkthru program by modifying the inputs before writing to the outputs. The file CTIP35.ZIP contains all the system files needed to test this application on your own EZ-LITE system. CTIP35.ZIP is available on the
FTP site. Files included in the ZIP file are: CTIP35.C SIGNAL.H, 2181_HDR.DSP TALK_47.DSP BUILD.BAT 2181.ACH The file TALK_47.DSP is an assembly routine that is called by CTIP35.C and initializes the interface between the ADSP-2181 and the AD1847. The file SIGNAL.H is a header file that contains macros for handling interrupts. 2181_HDR.DSP contains a modified run-time header for the 2181. BUILD.BAT is a batch file that assembles 2181HDR.DSP and then invokes the C compiler and all its CTIP35.C
/* CTIP 35 */ /* this program can be used as a shell for C programs running on the EZ-LITE board or as an basic example of C code */
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