For example, the low pass filter acting as a control smoother prior to the RDA instruction:
Code: Select all
rdax adcl,1
wra delay,0
clr
or 32767*256
mulx POT1
sof maxlength/1000,0
rdfx del_read, 0.0125
wrax del_read,1
wrax addr_ptr,0
rdfx del_read, 0.0125
and the source and meaning of the "magic" number 0.0125.
The knowledge base article on simple filters implies that the factor used in the RDFX instruction is (1 - e^(-2 * PI * f0/fs)).
So, if 0.0125 = (1 - e^(-2 * PI * f0/fs)), then (step by step)
e^(-2 * PI * f0/fs) = 1 - 0.0125 = 0.9875
take natural log of both sides....
-2 * PI * f0/fs = ln(0.9875) which is about -0.012579.
making f0 = 0.012579 * fs /(2 * PI)
= 0.012579 * 32768/(6.283) = 65.6 Hz.
Is this correct?