Received: by 10.224.223.14 with SMTP id ii14mr5462039qab.3.1350205255015; Sun, 14 Oct 2012 02:00:55 -0700 (PDT) Received: by 10.52.28.45 with SMTP id y13mr1374713vdg.10.1350205254918; Sun, 14 Oct 2012 02:00:54 -0700 (PDT) Path: r17ni24752519qap.0!nntp.google.com!l8no51065532qao.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.forth Date: Sun, 14 Oct 2012 02:00:54 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=178.27.34.143; posting-account=o1zNBwoAAABP2KiH5g6nPQp_sYWidVdt NNTP-Posting-Host: 178.27.34.143 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> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <7f13a1d3-a084-493e-9656-06fb12593f29@googlegroups.com> Subject: Re: GA144 polyForth From: Howerd Injection-Date: Sun, 14 Oct 2012 09:00:54 +0000 Content-Type: text/plain; charset=ISO-8859-1 On Saturday, October 13, 2012 11:30:44 PM UTC+2, rickman wrote: > On 10/13/2012 5:14 PM, Howerd wrote: > > > On Saturday, October 13, 2012 10:54:56 PM UTC+2, rickman wrote: > > >> On 10/13/2012 4:37 PM, Howerd wrote: > > >> > > >>> On Saturday, October 13, 2012 8:28:54 PM UTC+2, rickman wrote: > > >> > > >>>> On 10/13/2012 10:39 AM, Howerd wrote: > > >> > > >>>> > > >> > > >>>>> Hi Rick, > > >> > > >>>> > > >> > > >>>>> > > >> > > >>>> > > >> > > >>>>>> What sample rate do you plan to use? > > >> > > >>>> > > >> > > >>>>> I'm not intending to use the VCO as a conventional ADC, just observe the count as the voltage changes, so the sample rate will vary with voltage. Alos, mostly I want to measure timings. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> I'm not sure I follow that. How will you change your sample rate? BTW, > > >> > > >>>> > > >> > > >>>> unless I don't understand the why the ADC works, every time you read the > > >> > > >>>> > > >> > > >>>> ADC it stops the counter for a short time. Be aware of this as it may > > >> > > >>>> > > >> > > >>>> have an impact on your measurements if not accounted for. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>>>> I quickly read about OAM after reading your first post and I don't think > > >> > > >>>> > > >> > > >>>>>> it is in defiance to existing theory. > > >> > > >>>> > > >> > > >>>>> Yes, OAM is predicted by quantum mechanics, and was first observed in 1935 IIRC. > > >> > > >>>> > > >> > > >>>>> Very much existing theory. > > >> > > >>>> > > >> > > >>>>> > > >> > > >>>> > > >> > > >>>>> The theory that I want to get away from is where it is assumed that an electric field can be approximated by a scalar voltage. This may require 2, 3 or 4 receiving antennas and a transmitting antenna - measuring all signals in a synchronised way. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> I still don't see how the GA144 ADC is any different for this than any > > >> > > >>>> > > >> > > >>>> other ADC. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>>>> The issue with anti-aliasing is not eliminated, it is just addressed > > >> > > >>>> > > >> > > >>>>>> in the ADC method to some extent. > > >> > > >>>> > > >> > > >>>>> My plan is to make some measurements of timings on wires and antennas, present them on a PC using colorForth (booted from a USB stick using USBboot), then relate this to the theory... Anti-aliassing will no doubt come into this at some stage. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> Anti-aliasing is used to prevent signals above the Nyquist rate (1/2 > > >> > > >>>> > > >> > > >>>> your sample rate) from affecting your measurement of baseband signals. > > >> > > >>>> > > >> > > >>>> If you aren't sampling in the conventional sense, there is no need to > > >> > > >>>> > > >> > > >>>> anti-alias. But then I'm not clear what you *are* doing so I can't say > > >> > > >>>> > > >> > > >>>> for sure. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> Rick > > >> > > >>> > > >> > > >>> Hi Rick, > > >> > > >>> > > >> > > >>>> every time you read the ADC it stops the counter for a short time > > >> > > >>> There is no ADC, just a fast counter clocked by a VCO. > > >> > > >> > > >> > > >> And the name they give it is an "ADC". Analog in, Digital out... > > >> > > >> > > >> > > >> > > >> > > >>>> I still don't see how the GA144 ADC is any different for this than any > > >> > > >>>> other ADC. > > >> > > >>> Its no different to any other VCO and counter, but it is possible to pass the count value on to other cores to process, before passing it to the outside world. That and having five of these on each chip makes it very good for waht I want to do. > > >> > > >> > > >> > > >> The question is how will you make use of this data? If you aren't going > > >> > > >> to treat it as the digital equivalent of an analog waveform, just what > > >> > > >> is it? > > >> > > >> > > >> > > >> > > >> > > >>>> Anti-aliasing is used to prevent signals above the Nyquist rate (1/2 > > >> > > >>>> your sample rate) from affecting your measurement of baseband signals. > > >> > > >>> If I run the VCO flat out at 5GHz, using it as a over-sampled one-bit ADC this should be OK for 10 MHZ signals. If this is possible, of course - I may need to drop it down to 2.5GHz. > > >> > > >> > > >> > > >> This statement clearly shows you don't understand what a VCO is. You > > >> > > >> *don't* run the VCO "flat out". The frequency varies with the input > > >> > > >> voltage, the voltage you are trying to measure. The frequency varies > > >> > > >> with the input voltage and drives the counter. By reading the counter > > >> > > >> at known times you can subtract successive values getting the difference > > >> > > >> which corresponds to the average voltage in that time period. You can > > >> > > >> process the counter values as you wish, but the frequency of the VCO is > > >> > > >> not constant. > > >> > > >> > > >> > > >> How do you think the VCO works? Or are you planning to drive the VCO > > >> > > >> with Vss? Then what do you do with the input voltage? > > >> > > >> > > >> > > >> > > >> > > >>>> But then I'm not clear what you *are* doing so I can't say for sure. > > >> > > >>> Maybe you have guesed that I'm not clear how to achieve what I want ;-) > > >> > > >>> But my direction is clear : for each antenna measure the electrical signal on an input pin as using the minimum number of transistors possible. Look at what really goes on when electicity interacts with antennas. Play it by ear... > > >> > > >>> I would like to start by repeating Chuck's measurement of wire length by timing a pulse bouncing back from the end of the wire. > > >> > > >> > > >> > > >> Ok, that should be pretty simple, but make sure it is a long enough > > >> > > >> wire. The CPU is fast, but not that fast. The 700 MIPS number is a > > >> > > >> peak rate and you can't get too close to that with real code. > > >> > > >> > > >> > > >> Rick > > > > > > Hi Rick, > > > > > >> And the name they give it is an "ADC" > > > Yes, OK, I meant not a conventional ADC, i.e. not delta-sigma, successive approximation, integrating etc... > > > > > >> The question is how will you make use of this data? If you aren't going > > >> to treat it as the digital equivalent of an analog waveform, just what > > >> is it? > > > I want to interact with RF electrical signals using Forth, the same way I do with any other piece of hardware. > > > So I don't know what I will do with the data - it depends on what I find. > > > I am hoping it will be like firing up a new processor with Forth for the first time and probing its peripherals, checking what I see against the databook. > > > > > >> This statement clearly shows you don't understand what a VCO is. > > > No, it shows that I did not express myself clearly ;-) > > > I will probably run the VCO with an input voltage very close to Vss, and just look at the bottom bit of the counter. This will give me a 1-bit ADC with a 5 GHz sampling rate, if you want to look at it that way. > > > I want to detect the smallest possible voltage and time variations, then average them over human-scale time periods. I'm also not interested in absolute values of either voltage or time, just deltas. > > > > Then you are looking for resolution, not VCO speed. You can use the > > GA144 ADC for high resolution at very slow sample rates. But if you > > don't know what you are looking for, I'm not sure how you will know when > > you find it. > > > > Many other ADCs will give you very high resolution as well. > > > > > > >> The CPU is fast, but not that fast. > > > True, but its the VCO that determines the sampling rate - 5 GHz has a wavelength of 5.9 cm. 50 GHz would be better... > > > > The rate of the VCO is not the sample rate of the ADC. The VCO is > > analog at the interface to the input signal and the frequency is analog > > (continuously variable). It is the counter that is digital. > > > > Rick 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. > Many other ADCs will give you very high resolution as well. Digital resolution, yes, but analog resolution probably not. > 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 ). > The rate of the VCO is not the sample rate of the ADC It is if it is a 1-bit ADC, sort of. 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. 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 :-) Best regards, Howerd Best regards, Howerd