read_flash.c

来自「ADI 公司的DSP ADSP21262 EZ-KIT LITE开发板的全部源代」· C语言 代码 · 共 51 行

#include "Sample Playback.h"



//This subroutine reads one 16-bit audio sample from FLASH using
//core accesses of the PP. It fetches this sample from a byte address
//that is passed in as the argument bAddr.
void read_flash_samples (void)
{
    Csample* P2Sample;
    
    int temp;
    
    P2Sample = FirstSample;

    while(P2Sample){
        //configure general PP settings
        (*pPPCTL) = PPBHC|PPDUR20;
    
        (*pEIPP) = P2Sample->CurrentAddr;   //External Index
        (*pEMPP) = 1;                      //External Modify
        
        //and then or in bit's to initiate DMA
        (*pPPCTL) |= (PPEN);
        // (with PPEN = 1 and PPDEN =0 core read's of the RXPP buffer cause 
        //  the PP to fetch 32bits of data based on EIPP and EMPP.)
    
    
        //----CONDITION SAMPLE -----------------------
        // PP fetches 32bits, but only 16 msb's of data are valid (signed integer).
        // To convert to float, shift it right by 16 (first cast to int to maintain sign bit)
        
        //P2Sample->CurrentVal = (float)( (int)(*pRXPP) >> 16 );
    
        // To be clear for this example, above instr. is equivalent
        // to these:
        #if 1
            temp = (*pRXPP);        //fetch sample
            
            temp = temp >> 16;        //shift to lsb's
            P2Sample->CurrentVal = (float)temp;       //convert in to float
        #endif
            
               
        
        
        P2Sample=P2Sample->Next;
        
    }
}