Received: by 10.180.73.173 with SMTP id m13mr2113995wiv.4.1350258869363; Sun, 14 Oct 2012 16:54:29 -0700 (PDT) Path: q11ni134313897wiw.1!nntp.google.com!feeder2.cambriumusenet.nl!feed.tweaknews.nl!85.12.40.131.MISMATCH!xlned.com!feeder3.xlned.com!feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: rickman Newsgroups: comp.lang.forth Subject: Re: GA144 polyForth Date: Sun, 14 Oct 2012 19:54:23 -0400 Organization: A noiseless patient Spider Lines: 86 Message-ID: References: <32e7fd8d-7494-4010-a9d5-d9673a3df831@googlegroups.com> <7xzk409lb7.fsf@ruckus.brouhaha.com> <4fdeaae3-ea51-4a69-84fd-a163baab7c1d@googlegroups.com> <6f308d76-db3d-44d1-a554-6044add07705@googlegroups.com> <6076cfa4-6165-4e05-a2d1-8d09e018d805@googlegroups.com> <76323c32-6fd1-4032-9313-2af83667532e@googlegroups.com> <7f13a1d3-a084-493e-9656-06fb12593f29@googlegroups.com> Mime-Version: 1.0 Injection-Date: Sun, 14 Oct 2012 23:54:29 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="575a8d3a503cd2ab981bf514a483fac2"; logging-data="14011"; mail-complaints-to="ab...@eternal-september.org"; posting-account="U2FsdGVkX18ku8nQLrsotQs1tsVYVyfq" User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 In-Reply-To: <7f13a1d3-a084-493e-9656-06fb12593f29@googlegroups.com> Cancel-Lock: sha1:P37Ua56uCtvnYKLqbhVO58s7ni4= Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 10/14/2012 5:00 AM, Howerd wrote: > On Saturday, October 13, 2012 11:30:44 PM UTC+2, rickman wrote: >> > > Hi Rick, > >> Then you are looking for resolution, not VCO speed. > I am looking for both - detection of very small signals and very small time intervals. In the GA144 the time interval will be determined by the CPU speed, I think the best you might get is around 10 ns, but I don't recall exactly, this might be for a clock timed loop that just takes the data and passes it on. At that speed you will only get 4.3 ENOB (effective number of bits) theoretical max. That's not very sensitive. >> Many other ADCs will give you very high resolution as well. > Digital resolution, yes, but analog resolution probably not. Uh, yeah... right. It's time to learn about electronics. You can think that you are going to toss existing theory out the window, but this is not the area that needs to be reinvented in order to learn about... what was it you were exploring again? >> GA144 ADC for high resolution at very slow sample rates. > I think you are using "resolution" in two different ways - there is analog resolution ( ability to detect a given change in voltage ), and ADC resolution ( number of bits ). Yes, they are related by the gain of your amplifiers... uh, if you had amplifiers. In the GA144 integrating ADC the analog resolution will be related to the sample rate... if you have a sample rate. The faster the sample rate the lower the analog resolution. The 4.3 bits I mention above are over the analog range of about 1.2 volts, this is not well defined in the data sheet, so I'm not certain what this range is. The ADC has a non-linear curve with more resolution in the center which is what I am assuming will be used. Trying to get the full analog range of 1.8 volts uses the compressed ranges near the limits with very low analog resolution. The digital resolution is the number of bits. The analog resolution is the analog range divided by the number of bits. No magic, no new science to be invented. The two are directly connected. The only way to improve the analog resolution is to slow down the measurement to give longer integrations or to use an amplifier to get the same voltage range at the ADC input with a smaller range on the amplifier input. >> The rate of the VCO is not the sample rate of the ADC > It is if it is a 1-bit ADC, sort of. Ok, you can go ahead and think of this as a 1 bit ADC but that buys you the worst possible resolution at the highest sample rate. > Its the analog resolution that I am interested in. I presume that the GA144's VCO is just a handful of transistors, so the bottom bit of the VCO count represents some very small change in the charge at the input pin. No, the counter bits do NOT correspond to anything at the input. The counter free runs at a rate between about 3.5 GHz and 5.5 GHz. The raw readings just keep incrementing and the absolute values mean nothing. You get an ADC reading by SUBTRACTING one reading from the next. This DIFFERENCE is proportional to the integral of the voltage at the input over the sample period. Actually, the range of the VCO in the linear area is only about 1.3 or 1.4 GHz rather than the 2 GHz I used to calculate the ENOB. The frequency range is what determines the difference range and the ADC resolution. > Only with the GA144 do I get very sensitive analog inputs together with some fast processing, plus a high level (eForth or polyForth) IDE, all on chip. > I think this is magic :-) Yes, I expect it must seem like magic... Or you could listen to people who don't see it as magic, but rather understand the details and can explain how it works as if it were engineering... I'm pretty sure you won't see anything in your signals using the GA144 that you can't see as well if not better using other devices. For example, how well will your readings be time correlated using multiple ADCs in the GA144? I can't get an answer to questions like this. Or even how long the GA144 nodes take to come out of sleep when the input clock transitions. These are *very* important numbers when using the ADC for signal acquisition. Random delays here cause signal distortion/noise. Rick