PIC scope test1
in [Design]
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From: Jan Panteltje on 15 Mar 2010 12:48 PIC scope test1 This is the maximum aquisition speed I can get out of a PIC 18F14K22, 10 kHz sinewave: ftp://panteltje.com/pub/PIC_18F14K22_scope_10kHz_img_1876.jpg Not bad at all, if you realise it is 127 dots for about 5 periods. With 100 uS per period the display width is about 500 uS, that makes 500 uS / 127 = 3.9, say 4 uS per sample, or 250 kHz from the ADC. Trigger is rock solid too :-) Input is line level audio.
From: GiveMeL on 15 Mar 2010 15:40 I did a similar thing with a 18F2450 except that I streamed the samples to a PC via USB, at 64k samples per second. So I have unlimited storage =P
From: MK on 16 Mar 2010 04:12 "Jan Panteltje" <pNaonStpealmtje(a)yahoo.com> wrote in message news:hnlod6$c0v$1(a)news.albasani.net... > PIC scope test1 > > This is the maximum aquisition speed I can get out of a PIC 18F14K22, > 10 kHz sinewave: > ftp://panteltje.com/pub/PIC_18F14K22_scope_10kHz_img_1876.jpg > > Not bad at all, if you realise it is 127 dots for about 5 periods. > With 100 uS per period the display width is about 500 uS, > that makes 500 uS / 127 = 3.9, say 4 uS per sample, or 250 kHz from the > ADC. > > Trigger is rock solid too :-) > Input is line level audio. > > Hello Jan, Looking at your PIC scope I can't help but remember Dr Johnson's comment to Boswell on women preaching: Johnson: "Sir, a woman's preaching is like a dog's walking on his hind legs. It is not done well; but you are surprised to find it done at all." Jan - why a PIC ? Michael Kellett
From: Jan Panteltje on 16 Mar 2010 07:02 On a sunny day (Mon, 15 Mar 2010 12:40:11 -0700 (PDT)) it happened GiveMeL <pete.berglund(a)gmail.com> wrote in <7863c47e-99fd-4d27-932b-d912c66cc670(a)o3g2000yqb.googlegroups.com>: >I did a similar thing with a 18F2450 except that I streamed the >samples to a PC via USB, at 64k samples per second. So I have >unlimited storage =P Yes, unlimited storage is a nice feature. But I am not really an USB enthusiast. One thing I would like for my PIC scope is isolation from ground. Important for very small signals, and also when measuring on things that carry some volts. So I was thinking of using ethernet and sending UDP packets. Packet loss on LAN is not that likely, so UDP would do. Would take an extra chip, and not sure if I have enough memory to construct an UDP packet. And I find writing ethernet based programs on the PC in Linux much easier then using lib USB and writing USB drivers. Also it means the PIC scope system can be accessed remotely, when the PC is off. The advantage of USB is the 5 V, but already a lot hangs on the USB here. Walwarts are only about 5$.
From: Jan Panteltje on 16 Mar 2010 08:31
On a sunny day (Tue, 16 Mar 2010 08:12:12 -0000) it happened "MK" <mk(a)nospam.please> wrote in <2MGdndaBUab9oALWnZ2dnUVZ7sednZ2d(a)bt.com>: > >"Jan Panteltje" <pNaonStpealmtje(a)yahoo.com> wrote in message >news:hnlod6$c0v$1(a)news.albasani.net... >> PIC scope test1 >> >> This is the maximum aquisition speed I can get out of a PIC 18F14K22, >> 10 kHz sinewave: >> ftp://panteltje.com/pub/PIC_18F14K22_scope_10kHz_img_1876.jpg >> >> Not bad at all, if you realise it is 127 dots for about 5 periods. >> With 100 uS per period the display width is about 500 uS, >> that makes 500 uS / 127 = 3.9, say 4 uS per sample, or 250 kHz from the >> ADC. >> >> Trigger is rock solid too :-) >> Input is line level audio. >> >> >Hello Jan, > > >Looking at your PIC scope I can't help but remember Dr Johnson's comment to >Boswell on women preaching: > > Johnson: "Sir, a woman's preaching is like a dog's walking on his hind >legs. It is not done well; but you are surprised to find it done at all." > >Jan - why a PIC ? I wrote the graphics controller code, x, y plot for this LCD in PIC 18 ASM. The PIC has an ADC, why not try scope? Have 3 free input pins :-) Took only an hour to program the scope routine. I also have a Spartan2 connected to a 30 MHz video ADC, uses internal RAM and has a serial and UDP interface, but it has a character display :-) I could hang the graphics LCD with PIC on its serial out too. PIC scope code is just a library building block, like the graphics code. PIC is more powerful then you think, runs 64 MHz clock, 18F has some nice instructions to move data in RAM. Just fun to do some asm. And I can think of many applications that will have no problem, hoe about a live mains waveform monitor? Mains spike detector? Hart beat display? Not all has to be GHz for it to be useful you know, on the contrary! And PIC is cheap, easy to program, available everywhere, seems reliable too. No I do not work for Microchip :-) And hold no Microchip shares. Oh, and PIC uses extremely extremely and I repeat EXTREMELY little power. >Michael Kellett > > > > |