Thu Oct 29 11:57:37 CET 2009
PIC18F1220 with direct speaker attachment
It's possible to connect an 8 ohm speaker directly to the PIC output
pins as long as you switch it fast enough. I'm going to use this to
build a bridged circuit for a burgler alarm.
P1A / B3 - pin 20
P2B / B2 - pin 19
On the CATkit board these lead to R7 and R8.
The software: I'm copying synth-1220-8.fm to alarm-1220-8.fm
The app can reuse most of the synth lib. It just requires some
different config data and boot code.
R: I need to document standard practices. Building a library of
code and running a console with access is straightforward. But how
to do the boot process?
So, it's sputtering. Let's make the wiring optional.
I've changed it so that by default it drives the speaker in
full-bridge, but switches it off in the `engine-off' word to avoid DC