| Electronics > Projects, Designs, and Technical Stuff |
| Oscilloscope FPGA/MCU/FLASH/RAM Design |
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| Mechatrommer:
i'm trying to upload some picture here... wait... hmmm. cant upload in here. gotta use external link... ok... say i want to design an oscilloscope using FPGA+MCU+FLASH+RAM. which one is more likely/practical? method 1... or method 2? here, i wanna practice or implement what dave has thought me/us something about designing EE system using the box-box thing :) sorry for my limited vocab storage. sysmbols: FW = firmware HC = hardware calibration data (stored in Spansion Flash during in factory testing) SC = software calibration data (stored in Spansion Flash after doing manual re-calibration from FW menu by user) BFR = oscilloscope reading sent by FPGA to BlackFin MCU BFS = oscilloscope reading sent by BlackFin to LCD Display via Hynix RAM BF = BlackFin MCU method1 description: during operation, the FPGA will read through ADC and using HC and SC, it will calculate the BFR using generic formula: BFR = f(ADC, HC, SC) and be stored somewhere else (RAM?) or directly sent and to be fetched by BF. BF will send the BFS=BFR value for display method2 description: during operation, the FPGA will read through ADC=BFR and be stored somewhere else (RAM?) or directly sent and to be fetched by BF. BF will calculate the BFS value for display: BFS = f(BFR, HC, SC) as you can see: method 1: both FPGA and BF share the same Flash to read some data method 2: only BF access the Flash. FPGA is just a "dump S" logic gates doing its thing from inside so which one is more practical, easily, economy etc? p/S: i got this idea while reading a link suggested by other member: http://www.fpga4fun.com/digitalscope_hdl1.html |
| wd5gnr:
Do a Google on bitscope. Like most things I doubt you can duplicate what you get with something like the Rigol for the price. Not to say that I haven't frequently designed and built stuff that I could have bought cheaper ;-) |
| Mechatrommer:
"Not to say that I haven't frequently designed and built stuff that I could have bought cheaper ;-)" is that mean, buying the parts alone would be more expensive than buying the existing DSO? hmm. or is that difficult to design such a thing? ??? i googled a little bit, bitscope is about PC scope, am i wrong? i'm not interest on that, i want the type that directly show the result on screen, just like rigol and my case (question) here is quite simple, well... for EE ppl i think? which is better? method1 or method2? i'm not asking is my schematic is a complete super duper circuit? :) |
| alm:
--- Quote from: shafri on May 08, 2010, 02:54:51 pm ---is that mean, buying the parts alone would be more expensive than buying the existing DSO? --- End quote --- Possibly, especially if you want a 'large' (i.e. not 128x64 or so) display, proper controls and a case. --- Quote from: shafri on May 08, 2010, 02:54:51 pm ---hmm. or is that difficult to design such a thing? ??? --- End quote --- Yes, which is why none of the DIY scopes can even remotely compete with analog scopes from 40 years ago (eg. Tek 465), or the entry levels scopes from the big three (Agilent/Lecroy/Tektronix), or even the smaller brands like Rigol. Something like 100MHz/1GS/s is quite basic (and 100MHz analog scopes have been standard for a long time), and is pretty hard to achieve. DIY scopes usually have a sample rate that's much too low to be useful, and a vertical amplifier and attenuator up to 100MHz isn't easy either (possibly the hardest part). Even the $$$ top-end commercial Bitscope has a crappy real-time sample rate of 40MS/s. If you use the rule-of-thumb of bandwidth = sample rate / 10, you get an analog bandwidth of 4MHz! I consider them more as fast dataloggers (where it doesn't suck as much to be forced to use a PC interface) than proper scopes. --- Quote from: shafri on May 08, 2010, 02:54:51 pm ---i googled a little bit, bitscope is about PC scope, am i wrong? i'm not interest on that, i want the type that directly show the result on screen, just like rigol and my case (question) here is quite simple, well... for EE ppl i think? which is better? method1 or method2? i'm not asking is my schematic is a complete super duper circuit? :) --- End quote --- The difference between a PC-scope and a stand-alone scope is just the back-end, which is the easy part. No reason why you can't use a TFT screen and some controls with a bitscope front-end. The other difference is that all commercial PC-scopes are crap compared to the stand-alone ones, unless you get into the expensive (thousands of dollars) ones from NI/Agilent. I believe Dave talked about this in one of his videos. There's nothing wrong with building stuff yourself that's more expensive and has worse specs than commercial units, but don't expect it to come close to real analog or digital scopes. Plus you're going to need a scope to debug it ;). |
| Mechatrommer:
"which is why none of the DIY scopes can remotely compete with analog scopes from 40 years ago " i think this gotta be something relating to analog (continuous) vs digital (sampled) thing. if yes, then we have to wait "our" digital hardware designer to comeout with something that sample/output close to continuous system (very fast sampling rate, i dont know... 1000TSamples/sec at 1000THz maybe? ???) "and a vertical ampilfier and attenuator up to 100MHz isn't easy either (possibly the hardest part). " so doing a bitscope at this MHz will be darn difficult too! right? maybe i should change my question.... which one of the two methods above perform faster? or efficient? and i think i need to re-state the methods: method 1: both FPGA and BF share the same Flash to read some data method 2: only BF access the Flash. FPGA is just a "dump S" logic gates doing its thing from inside or maybe method2 statement is too vague... let me change the syntax method 2: only BF access the Flash. input of FPGA is just from ADC alone, NOT from Flash memory. Process it internally, and send the value to BF and the answer should be like... a) = method 1 (and some reason) b) = method 2 (and some reason) c) = your schematic is not enough to justify (and some reason) d) = i dont know! (then you shouldnt post ???) e) = i know... but i dont wanna post/share :) |
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