For didactical purposes i want to create a lowpass FIR filter (of any type, Equiripple will be ok) that attenuate an ‘omega1’ frequency (example: 0.3 rad/s, normalized) of at least 80 dB.

I know that for IIR Butterworth filters there is a function called “buttord”, which compute the cut frequency and the minimum order required by the IIR filter by knowing:

1. The edge of the pass band
2. The edge of the stop band
3. Maximum ripple allowed in the passband
4. Maximum ripple allowed in the stopband

I’m looking for something similar for FIR filters, in order to compute filters coefficients by fir1 or firpm functions.
I managed to design my filter using the filterDesign graphical tool of MATLAB, but I’m trying to entirely design the filter by code scripting.