>Anybody built an d/a convertor out of the USART and and integrator before
>or am I the first (I mean, with a PIC. I know SACD works roughly this
>way)?

You are not. I used it for speech output. You can wire a headphone speaker
directly to a RS232 output. I used PWM not sigma-delta, what you seem to
be trying, at 115.2kBauds, and xor-modulated it with a block of white
noise so there was no whistling. The driver was simply a user mode program
driving a standard comms port by opening a file and writing to it.

The interesting part is to do it the other way around, a/d using the
serial input. I do not know how this could be done but something clever
involving 'modulation' from TxD could be devised.

Peter

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