> What do you think an effective means of decreasing output volume
> for short chirps?

Decreasing the pulse width will decrease the volume as a lot of the
bass and mid-range content will be gone

AIUI, the NCO can operate in Fixed Duty Cycle Mode or Pulse
Frequency Mode. In PF mode, you have output pulse width control,
ie a PWM-esque function, via 3 bits in NCOxCLK

bit 7-5 NxPWS<2:0>: NCOx Output Pulse Width Select bits

111 =3D 128 NCOx clock periods
110 =3D 64 NCOx clock periods
101 =3D 32 NCOx clock periods
100 =3D 16 NCOx clock periods
011 =3D 8 NCOx clock periods
010 =3D 4 NCOx clock periods
001 =3D 2 NCOx clock periods
000 =3D 1 NCOx clock periods

It seems to me that for normal operation you'd be in FDC mode and
in PF mode for a quiet test. Flipping the NCOxCON,NxPFM bit looks
like that would toggle between normal/test

Joe


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