I come from a physics background, so I have lots of theory, but basically nothing as it applies to reality. So, yes, I know about things like fourier analysis and all the theory behind it, but how it applies to circuits is something I'm still learning from the ground up. I make not claim to know what I'm doing with digital sampling. I'm learning completely from scratch here... So I then take it that what you're saying is that if you're sampling at 100 Hz, the useful fourier coefficients are only the ones up through the first 50 wavenumbers. (Watch me be wrong again) As for the 16F88, it was a cheap programmer kit, that came with a 16F88. So, if it doesn't do what I want, I'll buy the 30F4012 and continue. To be honest, I'm really quite broke right now waiting for a check from a lot of work I did earlier this year, so the fact that this kit was 30$ instead of a more advanced programmer that can program the 30 series was the difference between being able to work on this now and working on it in a few weeks. So, while I'd love to get the right tool for the job immediately, I don't have the money for it, yet. In any event, this will let me get started and learn about how to filter the PWM output. Then, when and if I need to, I can upgrade to the bigger chip. I assume it will have very similar usage of PWM and ADC registers, as well as very similar, if not equivalent, instruction set? -David -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Olin Lathrop Sent: Monday, July 18, 2005 4:55 AM To: Microcontroller discussion list - Public. Subject: Re: [PIC] Looking for a PIC with ADC, DAC, and UART... David de Regt wrote: > Ohhh, you mean like if I was tossing in a sin wave or something, I can't > send anything useful at more than 50 Hz due to sampling errors, I'll get > weird beat patterns and utter nonsense output. Yeah, okay, I know about > that. I wasn't even thinking about that. I'm not outputting sine waves > or anything, just voltage levels. Argh. You really do need to learn something about signal theory before trying to mess with filters. Go look up Fourier. You *are* sending sine waves. It's just that you are sending many of them superimposed so that your signal doesn't look sinusoidal anymore, and mix of sine waves is varying over time. But you can still analyse the signal as a summation of independent sine waves. Again, go look up Fourier. > Believe it or not, I know exactly what I'm doing, Maybe with your car, but you've got a lot to learn about signal processing and engineering in general. > In any event, last night I ordered a simple dev kit and a PIC16F88 for > 30$, which looks to do what I want. Hmm, well it probably can. Note that the 16F88 PWM is 6 times slower than that of the 30F4012, but I think your requirements are low enough that the 'F88 can get the job done as far as analog input and output. Don't come complaining to me though when you can't get all the floating point math to run at the speed you want. This might be exactly the right chip for a volume production design, but I don't understand why you don't want to give yourself a little more headroom for $3-4 total on this one-off project. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist