Hello,
I haven't used these forums for several years, I like the changes. However, I vaguely remember that there used to be a forum for PIC related programming? Is there no longer anywhere available for those questions?

Also, if anyone can suggest a really helpful forum (like this one) dedicated to PIC (or similar) that would be great.

Furthermore, maybe someone can help me with the following:
I'm thinking of making some data acquisition systems. They need to be able to do 12 bit ADC at 500Ksps, write the data to memory (we're talking sample times of the order of 1s, so need to address memory of the order of MB I think). The system then needs to output the data later on via a serial link or similar. I only have a few channels available to me to control the system and read data from the system.

From what I gather this is quite a big project, possibly too big. If anyone knows of any suitable chips (most PICs I have seen don't have the necessary sample rates), or suitable approaches, or somewhere I can get help that would be fantastic. I'm a novice!

Thank you
Posted on 2007-06-13 03:47:50 by adamjjackson
dsPIC is your answer: most have 12bit ADC, although I'm not sure if any reach 500KS/s. Check the datasheets, if none does, you can use an external converter, or some filter, since you're storing 1 sample per second anyway, as far as I can read, and thus you're prolly filtering the data via software. Why do you need 500KS/s anyway? I think all dsPIC reach 100KS/s with no problems though.

Posted on 2007-06-13 04:20:33 by Maverick
Hello.

Sorry I wasn't very clear. I need to sample at 500Ksps for a total time of 1s, so I am storing 500K samples per second. I need to sample that fast because of the nature of what I'm sampling. The run time of the experiment is of order 200ms, and I'd like to sample for a while either side. Unfortunately 100Ksps is too slow, otherwise I think it would be quite a bit easier.

I had considered an external ADC, but as I'm a complete novice I'm not sure how much extra designing, programming and testing it would take...?

Thanks
Posted on 2007-06-13 07:02:32 by adamjjackson
After a quick look at the datasheets,
dsPIC33FJ12GP201 : 500Ksps @ 12-bit,...
Same ADC performance:
dsPIC33FJ12GP202
PIC24HJ12GP201
PIC24HJ12GP202

it's mind-boggling how cheap these MCUs are o_O. Your oscilloscope will prolly cost less than $30 :)

Couple that with SRAM , and a USB controller (optional)
I'm not sure if SDRAM will be good to the timing. (its internal 15Hz refresh-cycle might get in the way)


You can decide on what SRAM to use by the Semiconductors catalog here: (it's an online shop)
http://www.mouser.com/index.cfm?handler=catalogdownloads
(though, the number of manufacturers there is very small)

Posted on 2007-06-13 11:25:16 by Ultrano
Hi, thanks for the advice. I think I had seen those chips, but was put off by the high pin count! I guess it can't be too hard...

I'll see how I get on.

Cheers
Posted on 2007-06-18 07:47:34 by adamjjackson