AD & DA
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From: Kari Laine on 31 Jan 2010 05:55 Hi, I am wondering how AD- and DA-converters are implemented. Any documents about the chips internal configuration? Would it be in theory possible to implement them with discrete components? Best Regards Kari PIC - ARM - DISPLAYS - RELAYS - MODULES - CONVERTERS - I2C - SPI - KEYPADS - ACCESSORIES http://www.byvac.com (I am just a satisfied customer)
From: Bob Masta on 31 Jan 2010 09:36 On Sun, 31 Jan 2010 12:55:50 +0200, Kari Laine <klaine8(a)gmail.com> wrote: >Hi, > >I am wondering how AD- and DA-converters are implemented. >Any documents about the chips internal configuration? >Would it be in theory possible to implement them with discrete components? Indeed it would be possible, and of course that's how it was done originally. Nowadays chips are more practical for most applications, but simple pulse averaging D/As are still used on the outputs of microprocessors that don't have true D/As built in. On older systems with parallel ports, you can make a simple 8-bit D/A with a handful of resistors. See <http://www.daqarta.com/dw_ggdd.htm> for a discussion of simple D/A circuits. With a D/A in hand, you can turn it into an A/D via "successive approximation", where the system (computer, or internals of A/D chip) toggles the D/A bits as it compares the D/A output to the input signal. When they match close enough, that bit pattern is the converted A/D value. See <http://www.daqarta.com/dw_ggaa.htm> for more info. Best regards, Bob Masta DAQARTA v5.00 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, FREE Signal Generator Pitch Track, Pitch-to-MIDI DaqMusic - FREE MUSIC, Forever! (Some assembly required) Science (and fun!) with your sound card!
From: Kari Laine on 31 Jan 2010 10:52 Bob Masta wrote: > On Sun, 31 Jan 2010 12:55:50 +0200, Kari Laine > <klaine8(a)gmail.com> wrote: > Bob Masta > > DAQARTA v5.00 > Data AcQuisition And Real-Time Analysis > www.daqarta.com > Scope, Spectrum, Spectrogram, Sound Level Meter > Frequency Counter, FREE Signal Generator > Pitch Track, Pitch-to-MIDI > DaqMusic - FREE MUSIC, Forever! > (Some assembly required) > Science (and fun!) with your sound card! Thanks Bob! Your product is interesting. How about Linux version? My hobby at the moment is to write Linux software for the Velleman PCSGU250 scope. It is not much yet. My math is poor so I have to study little to be able to do the Fourier and sin(x)/x stuff. I don't even yet to know what that sin(x)/x stuff is for... Happy hacking to you ! Kari -- PIC - ARM - DISPLAYS - RELAYS - MODULES - CONVERTERS - I2C - SPI - KEYPADS - ACCESSORIES http://www.byvac.com (I am just a satisfied customer)
From: CC on 31 Jan 2010 12:28 "Bob Masta" <N0Spam(a)daqarta.com> wrote in message news:4b658f7c.1184126(a)news.eternal-september.org... > On Sun, 31 Jan 2010 12:55:50 +0200, Kari Laine > <klaine8(a)gmail.com> wrote: > >>Hi, >> >>I am wondering how AD- and DA-converters are implemented. >>Any documents about the chips internal configuration? >>Would it be in theory possible to implement them with discrete components? > > Indeed it would be possible, and of course that's > how it was done originally. Nowadays chips are > more practical for most applications, but simple > pulse averaging D/As are still used on the outputs > of microprocessors that don't have true D/As built > in. > > On older systems with parallel ports, you can make > a simple 8-bit D/A with a handful of resistors. > See <http://www.daqarta.com/dw_ggdd.htm> for a > discussion of simple D/A circuits. > > With a D/A in hand, you can turn it into an A/D > via "successive approximation", where the system > (computer, or internals of A/D chip) toggles the > D/A bits as it compares the D/A output to the > input signal. When they match close enough, that > bit pattern is the converted A/D value. See > <http://www.daqarta.com/dw_ggaa.htm> for more > info. > > Best regards, > > > > This post just got me thinking about the A/D concept. Just curious about the basic concept (in 1 or 2 paragraphs). I think I understand how the process works but just wondering if you sample a microphone and store its value, that single sample represents the amplitude of the wave at that time and the frequency is reconstructed by stringing multiple samples together. I hope this is clear. I guess another way of saying this is how are both the amplitude & freq derived from a single number (please keep it simple).
From: Michael Black on 31 Jan 2010 14:34
On Sun, 31 Jan 2010, Kari Laine wrote: > Hi, > > I am wondering how AD- and DA-converters are implemented. > Any documents about the chips internal configuration? > Would it be in theory possible to implement them with discrete components? > There's very little that came about because of ICs. Most of them are based on things that existed before ICs. The problem is that a lot of those things were not practical in the days of tubes or even transistors, they existed but either only in the laboratory or in very expensive equipment, because it took up too many parts and too much space. So synthesized tuning of radios was possible in the old days, but it was only in very high end commercial equipment, but once ICs allowed for high integration, they became common and indeed have certain advantages in terms of cost and space (now they actually use up less space than analog tuning did). Even with things relatively recent, they often existed as discrete components or at least using very common low integration ICs. So as others have pointed out, D/A converters were in the form of a latch on a databus and a set of resistors, and once you had that you could add a comparator and use the computer to control the D/A converter and make an A/D converter. Or even do it without a CPU, requiring more hardware. Digital Signal Processing was being done before ICs to handle the task came along. A lot of the lowering of prices of consumer electronics comes because the design goes through a few iterations. So a first VCR or computer used a lot of common ICs that weren't very high density, and the cost and size of the equipment would reflect that. As sales rose, the manufacturer could afford to go to higher density components, which also cut manufacturing costs, so the ICs become higher density and less generic. That often happens a few times until there are virtually no parts in a piece of equipment, and the ICs can't be used except for that very specific use. Michael |