[sdiy] Simple clip detect LED circuit

[Seb Francis]

Hi John,

John Luciani wrote:
>
> Does the ADC output a fullscale code for input voltages that exceed its
> fullscale threshold? If so you could use the output of the ADC to 
> indicate
> when you have clipped. This will decrease your usable fullscale by
> 1LSB (which may not be exceptable for a low resolution ADC). The
> advantage of losing 1LSB of range is no measurement circuitry is
> required (only the LED oneshot).
>
It's a 24bit ADC (CODEC) and I'm only interested in 16bits, so it's 
definitely not a problem to loose 1LSB of range.  This was my original 
preferred way of doing things, but unfortunately the PIC that is 
interfacing with the CODEC has only 1 spare I/O pin, and I need to drive 
2 LEDs (1 for each channel).

Maybe I will look again at trying to free up another I/O pin.  I've 
already had to multiplex the SRAM addressing via a latch due to I/O 
shortages.  The only other possibility that occurs to me now is to use 
the Latch Enable signal to select which LED is to be driven.  I wonder 
if it would be ok to drive the clip LEDs at 48,000kHz?  I don't think 
it's ideal from a noise point of view ...

Seb