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Klaas Robers wrote:If you choose the samplig frequency of the FIR-filter 8 times the cut off frequency, so cut off frequency = 1 kHz and sampling frequency = 8 kHz, then you may choose coeficients of a sync (sin(x) / x) function.
Then you will see that 1 out of 4 coefficients = zero, so you may skip that multiplication.
Klaas Robers wrote:And the coefficients are symmetrical around the central tap, so you can first add the two samples and then do one multiplication. That will reduce the number of multiplications by two. This is a trick that I heard last weekend.
Steve Anderson wrote:......... The comparators in this device can generate an interrupt on a positive-going output, a negative-going output, or both...I'll be using the 'both' option.
Klaas Robers wrote:But the 18f.... has a hardware multiplication, you will need that for a FIR-filter. Without that you have lack of time.
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