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Without seeing your code I cannot know for sure, but I had a similar issue and after looking through teir code realized that the 64x dsplib Fir function uses the input vector for new samples AND previous samples, delay buffer, so YOU must manage the delay buffer after each call to the FIR function.

This is different from the 54x dsplib fir functions that had an additional input argument specifically for a delay buffer and it handled the moving of samples.

I'll give you an example of what I ended up doing for a 64 tap FIR using DSP_fir_gen, even with the two memcpy's it's far more efficient than doing an FIR in C with -o3 on the 6412:

//pSampbuf = pointer to 16 new input samples
#define NUM_SAMPLES 16
#define FIRTAPS 64

// Fir input AND delay buffer
short fir_indb[NUM_SAMPLES+FIRTAPS-1];

// Fir coefficients
short fir_coeff[FIRTAPS]; // Coeffs set at runtime

// New samples must be last in buffer
memcpy( &fir_indb[FIRTAPS-1], pSampbuf, NUM_SAMPLES*sizeof(short) );

// Perform FIR
DSP_fir_gen(fir_indb, fir_coeff, pSampbuf, FIRTAPS, NUM_SAMPLES);
// pSampbuf now contains 16 FIR new output samples

// Shift Delay buffer Samples from bottom to top
memcpy( &fir_indb[0], &fir_indb[NUM_SAMPLES], (FIRTAPS-1)*sizeof(short) );

Hope this helps,
Ten




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