Re: ADC Help

Hi Jan,

Would that work with a non repetitive signal of varying amplitude ?

The sound card suggestion is a good one. It would be better than my old analog scope since I could capture a number of examples and compare them.

Thanks for that. It would never have occurred to me.

On a sunny day (Sun, 20 Jan 2008 18:42:36 +0000) it happened Baron wrote in :

Sure, say if the ADC runs from unsigned 0 to 255 (8 bits), and 127 decimal is about the 'zero' (neg numbers have MSB set), then you can do something like check if the signal is lower then say 120, and, if so, consider that 'trigger'. It depends on noise levels etc where you want to slice. If you slice at 70 then only a much bigger signal will be considered trigger. And you can slice for the negative part too, of course, so you do not miss a signal that starts with a negative transition. For example:

. -- 255 . . . .--------------------- 156 trigger level . . . -- 127 zero signal level . . ---------- 100 trigger level . . . -- 0 loop:

level = read_adc();

trigger = 0; if( level < 100) trigger = 1; // detect any positive fluctuation if( level > 156) trigger = 1; // detect any negative fluctuation if(trigger) process_it_all();

goto loop

I see! That bit makes sense to me now!