http://forums.leaflabs.com/topic.php?id=2302 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:27:07 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=2302#post-12104 Sun, 29 Jul 2012 18:54:26 +0000 gbulmer 12104@http://forums.leaflabs.com/ <p>RockyLi - I can't give you much more advice without some more details.</p> <blockquote><p>Since Maple's clock frequency is 72MHz, I just wonder could I sample the signal at Clock Frequency.</p></blockquote> <p>Maple's ADC's sample at 1Msps, under ideal conditions, so almost 2 orders of magnitude too slow.</p> <p>Do you have to continuously calculate the FFT, or is it more like a batch operation, i.e. sample , then calculate the FFT, display it, then start again?</p> <p>Have you coded the FFT and measured it? What is the ratio of calculation/sample? Once you know that, you'll be aqble to estimate how much computer power is needed.</p> <p>I'd want as much computing headroom as I could get. I am not an expert but I'd want more than 10x, or more, computing vs samples; trying to make something work with not quite enough computer power is horrible.</p> <p>TI makes a lot of DSP's, and some folks I know liked Analog Devices BlackFin. If the problem is straightforward FFT and display, then a 'proper' DSP might be effective.</p> <p>Personally, I'd get the code for the FFT working, do some measurements, and then look for the right amount of computer power.<br /> I could imagine something like a Raspberry-Pi might be okay, but there are some other great ARM boards based on TI. </p> http://forums.leaflabs.com/topic.php?id=2302#post-12103 Sun, 29 Jul 2012 15:04:13 +0000 Anonymous 12103@http://forums.leaflabs.com/ <p>Thanks for your reply. Gbulmer.<br /> I know the Shannon theorem. But I am rookie at hardware thing with maple. Since Maple's clock frequency is 72MHz, I just wonder could I sample the signal at Clock Frequency. If so, this is JUST OK. I am thinking use a DSP chip or something which would be much more better. Do you have any advice about DSP chip to do the FFT? In my project, I need to do the FFT on the signal and display that value on LCD </p> http://forums.leaflabs.com/topic.php?id=2302#post-12095 Sat, 28 Jul 2012 19:09:00 +0000 gbulmer 12095@http://forums.leaflabs.com/ <p>RockyLi - The frequency is 20MHz to 30Mhz? What resolution do you need the measurements?</p> <p>That frequency must be sampled at faster than 60MHz (Nyquist–Shannon <a href="http://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem)" rel="nofollow">http://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem)</a>. My knee-jerk reaction is Maple is not the tool.</p> <p>Do you need analogue data, or will something digital, like zero-crossings of the signal, be enough?</p> <p>(Full disclosure: I am not a member of LeafLabs staff.) </p> http://forums.leaflabs.com/topic.php?id=2302#post-12082 Sat, 28 Jul 2012 00:46:52 +0000 Anonymous 12082@http://forums.leaflabs.com/ <p>Hi, everyone. I have one question here. In my project, I need to analyze the spectrum of beat signal output from photo detector, the frequency would be around 20Mhz-30Mhz. I want to confirm that whether I could do this with Maple board coz I am not familiar with the sample frequency of this board. Also, could anyone give me one link to the DPS stuff on this forum. I tried to search but got nothing useful. Thank you </p>