| Author |
Message |
Davide
Guest
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 Posted:
Tue Dec 06, 2005 11:47 pm Post subject:
Re: USB digital scope |
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Dear Uwe,
I think the project on Sourceforge should be the better choice. I never
opened a new project and I don't know how to proceed, but in any case I
try....
Hi,
Davide
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Marte Schwarz
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Hi Dave,
The PCB is intended to mount also two 12 bit 50MSPS A/D converter (I do
not yet tested this A/D converter but I hope this works fine...) in
place of the two 12 bit 20MSPS; The PCB has an "expansion port" for a
daughter board for:
1. An arbitrary waveform generator (the scope lose one channel)
2. A 16 bit digital port for analog/digital mixed oscilloscope function
(the scope lose one channel)
3. To stack multiple board in order to have 4,6 or 8 channel scope.
this sounds very very cool...
Marte |
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Helmut Sennewald
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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"Helmut Sennewald" <helmutsennewald@t-online.de> schrieb im Newsbeitrag
news:dn2g58$t1m$00$1@news.t-online.com...
| Quote: | "Davide" <davide.fiorini@gmail.com> schrieb im Newsbeitrag
news:1133819742.561981.317610@o13g2000cwo.googlegroups.com...
Hi Helmut,
I try to summarize the DSO features (let me know if you have particular
questions about some points)
Digital storage oscilloscope features:
- Data connection via USB 1.1/2.0 (FTDI - FT245BM)
- All DSO function are under PIC (16F8777) and FPGA (ALTERA Acex -
30Kgates)
- DSO A/D converter: 2 channels/12 bit: 20MSPS Real Time - 1GSPS
equivalent time
- TTL external trigger
- Timebase from 200ns/div to 2sec/div, over 100ms/div roll mode
- Vertical scale from da 50mV/div to 50V/div
- Channel coupling DC,AC,GND
- Data acquisition: sample, low pass filtering, peak to peak
- Trigger from CH1,CH2 or EXT
- Tigger mode NORMAL,AUTO,SINGLE
- FPGA configuration via USB (possibility to change the DSO firmware in
any moment)
- Powered via USB
- Small dimensions (145mm X 85mm X 30mm)
How can I send to the group the schematics, the images or some other
attachements?
Hi,
Davide
hi,
Davide
Hello Davide,
Thanks for this info. I am interested to see the hardware design.
Could you please send me the schematics/photos. I promise not
to use it commercially.
Best regards,
Helmut
|
----- Original Message -----
From: "Helmut Sennewald" <helmutsennewald@t-online.de>
Newsgroups: sci.electronics.design
Sent: Monday, December 05, 2005 11:49 PM
Subject: Re: USB digital scope
| Quote: | "Davide" <davide.fiorini@gmail.com> schrieb im Newsbeitrag
news:1133819742.561981.317610@o13g2000cwo.googlegroups.com...
Hi Helmut,
I try to summarize the DSO features (let me know if you have particular
questions about some points)
Digital storage oscilloscope features:
- Data connection via USB 1.1/2.0 (FTDI - FT245BM)
- All DSO function are under PIC (16F8777) and FPGA (ALTERA Acex -
30Kgates)
- DSO A/D converter: 2 channels/12 bit: 20MSPS Real Time - 1GSPS
equivalent time
- TTL external trigger
- Timebase from 200ns/div to 2sec/div, over 100ms/div roll mode
- Vertical scale from da 50mV/div to 50V/div
- Channel coupling DC,AC,GND
- Data acquisition: sample, low pass filtering, peak to peak
- Trigger from CH1,CH2 or EXT
- Tigger mode NORMAL,AUTO,SINGLE
- FPGA configuration via USB (possibility to change the DSO firmware in
any moment)
- Powered via USB
- Small dimensions (145mm X 85mm X 30mm)
How can I send to the group the schematics, the images or some other
attachements?
Hi,
Davide
hi,
Davide
Hello Davide,
Thanks for this info. I am interested to see the hardware design.
Could you please send me the schematics/photos. I promise not
to use it commercially.
Best regards,
Helmut
|
Hello Davide,
Thanks for sending your schematic to me. I have taken a look to it.
I have read in another message from you that this circuit
can save 1k-samples per channel.
Is it possible to have a higher number of samples stored
with a pin-compatible FPGA?
Best regards,
Helmut
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Davide
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Hi Helmut,
it is possible to fit in the same pcb the ACEX1K50 in place of the
1K30: in this case the memory for each channel is increased to 1.5K
samples.
Davide |
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Bob Smith
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Davide wrote:
| Quote: | Dear Bob,
thanks for your offer. I saw the linuxtoys.org website, and this is
very interesting. I'm thinking about the functions to include in the
applicative. I'm not a software specialist and the "XMLHttpRequest()
for your interface..." is not very clear for me....
|
XMLHttpRequest() is a JavaScript subroutine (so it runs
on the web browser) that monitors the web server for new
data. It does this without polling so it is very fast.
This routine is the core of what is called AJAX and is
what makes sites like Google maps work.
A web interface is just one possibility. We could also
to a TCL interface if you wish. We probably can't do
native X-windows or MS-windows interfaces since you'll
almost certainly want a portable interface.
Bob |
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Joel Kolstad
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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"Marte Schwarz" <marte.schwarz@gmx.de> wrote in message
news:dn4qtr$jov$1@news2.rz.uni-karlsruhe.de...
| Quote: | The PCB is intended to mount also two 12 bit 50MSPS A/D converter (I do
not yet tested this A/D converter but I hope this works fine...) in
place of the two 12 bit 20MSPS; The PCB has an "expansion port" for a
daughter board for:
3. To stack multiple board in order to have 4,6 or 8 channel scope.
|
I've thought about doing something like this myself on and off, but there's a
couple of challenges with the approach:
-- Aligning all the paths from one box to the next pretty much implies that
you need to generate a common clock somewhere and distribute it to all the
individual boxes with some known relation from box to box. If you do restrict
people to physically plugging one box into the other (or connecting them only
with cables of known lengths that you've provided), this is not difficult.
-- You need to distribute a high speed "trigger" signals to all the boxes so
they know when to stop capturing. That's not too hard, but what's harder is
that you have to consider whether or not you want every box to be able to
trigger or whether you just want to have a specialized "trigger" box... the
problem is that, while repetitive random-time sampling is great (with
repetitive signals), your trigger circuitry has to operate at the "equivalent
time" rate, i.e., much faster than the ADCs themselves.
-- With digital (logic analyzer) boxes, it becomes challenging to start
coordinating triggers when the trigger event is something like, "bit pattern
1010xxxx on box #1, then 00xxxx00 on box #3, back to xx0xxxxx on box #1,
etc..." (And this is a very simple trigger event compared to what contemporary
logic analyzers can do.)
At the end of the day I figured it's be easier just to design one big PCB and
populate it differently based on the options a user wants, just like the big
boys do. :-) I think there's a huge market out there for a USB-based
instrument that implements most of what something like a Tektronix TDS3054
does -- 4 analog channels, 500MHz analog response, 5GSsp. With '3054s going
for $10k, if you could profitably sell a USB-based version for, say, $2500,
you'd have more orders than you could fill, I imagine!
The Bitscope guys (www.bitscope.com) out of Australia have been quite
successful, even though their products are nowhere near as fancy as a TDS3054
(they're basically 100MHz/100Msps with ONE channel and something FAR less with
two channels).
---Joel Kolstad |
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Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Davide wrote:
| Quote: | Hi Helmut,
I try to summarize the DSO features (let me know if you have particular
questions about some points)
Digital storage oscilloscope features:
- Data connection via USB 1.1/2.0 (FTDI - FT245BM)
- All DSO function are under PIC (16F8777) and FPGA (ALTERA Acex -
30Kgates)
- DSO A/D converter: 2 channels/12 bit: 20MSPS Real Time - 1GSPS
equivalent time
- TTL external trigger
- Timebase from 200ns/div to 2sec/div, over 100ms/div roll mode
- Vertical scale from da 50mV/div to 50V/div
- Channel coupling DC,AC,GND
- Data acquisition: sample, low pass filtering, peak to peak
- Trigger from CH1,CH2 or EXT
- Tigger mode NORMAL,AUTO,SINGLE
- FPGA configuration via USB (possibility to change the DSO firmware in
any moment)
- Powered via USB
- Small dimensions (145mm X 85mm X 30mm)
How can I send to the group the schematics, the images or some other
attachements?
Hi,
Davide
hi,
Davide
|
Hi Davide,
An interesting project,
I dont see the memories, how deep are they/ or all sampling are sent to
PC in real time? What do you mean "1GSPS equivalent time"?
Also I would like to see the schematic, have you posted it somewhere
yet?
Regard, |
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Davide
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Hi,
I used the memories inside the Altera. Each channel has a memory for 1K
sample, 512 samples in case of peak to peak sampling. The length of the
sweep is 512 samples. I implemented a random sampling using a
sub-interpolation for the trigger time. In this way is possible to
sample only repetitive signals using an equivalent time of 1ns. I don't
know how to post the schematic, I can send this directly to your
e-mail, if you want.
hi,
Davide |
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Marte Schwarz
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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I disagree Jörg,
| Quote: | With all due respect that isn't going to be nearly enough for today's
designs. 20nsec may be ok if there is enough screen resolution. But you
don't really need 12 bits for a scope so maybe a trade-off towards higher
speed and less bits could be a future thought.
|
12 bits are very good for some things. I hate these lazy 8 bit scopes. 20 ns
would be fine too, but I don't need these high frequencies very often.
Marte
who is very interesting too... |
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Davide
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: USB digital scope |
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Dear Joel,
thanks for your considerations: you are right, the channel
synchronization is VERY difficult...I approached this problem in this
way:
1. I distribute the clock signal (20MHz) from the first scope board
(channel 1 and 2) to my second board (channel 3 and 4). The clock goes
only to fpga (then the fpga distribute them to the A/Dcs), and for this
the capacitive loading on this wire is quite low.
2. I have a bidirectional wire, the trigger, that comes from first
board to the second if the trigger is on channel 1 or 2 or from the
second board to the first if the trigger is on channel 3 or 4 (this is
set by the applicative program). The trigger is a "normal" signal
synchronous with the 20MHz clock signal: this will generate the sweeps
with exactly the same start point and the same end point (referred to
the 20MHz clock cycle).
3. The equivalent time sampling will be rebuilt after this phase,
calculating with interpolation the trigger instant on a sub-cycle basis
(interpolation) and shifting the overall waveform of this fractional
value. For this the waveforms from the different boards needs to be
synchronized at the clock cycle and not at higher frequency.
Finally, this scope has not very high features but from my point of
view is quite cheap (about 100€ for components) and easy to use
(powered by USB only). Another very important point (always from my
point of view) is the "teaching" peculiarity of this instrument: you
can change the DSO firmware (FPGA) directly from the USB with no
programmers or other things, only Quartus and a USB cable.
hi,
Davide |
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Riscy
Guest
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| Posted:
Thu Dec 08, 2005 9:35 am Post subject:
Re: USB digital scope |
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Marte
What is the part number of the ADC you just mention below
Why not one 16 bit and one 12 bits, it give best of two(!)
Riscy
Marte Schwarz wrote:
| Quote: | Hi Dave,
The PCB is intended to mount also two 12 bit 50MSPS A/D converter (I do
not yet tested this A/D converter but I hope this works fine...) in
place of the two 12 bit 20MSPS; The PCB has an "expansion port" for a
daughter board for:
1. An arbitrary waveform generator (the scope lose one channel)
2. A 16 bit digital port for analog/digital mixed oscilloscope function
(the scope lose one channel)
3. To stack multiple board in order to have 4,6 or 8 channel scope.
this sounds very very cool...
Marte |
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Riscy
Guest
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| Posted:
Thu Dec 08, 2005 9:35 am Post subject:
Re: USB digital scope |
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Hi I'm very interested on these DLL, how to try out these module, can
they be intergrated into C# code from VS 2003 pro?.
What kind of AD are you using?
Regards
Davide wrote:
| Quote: | Hi,
I'm reading from the USB port using the D2XX functions from FTDI. I
installed the driver for the FT245BM chip, and I use the D2XX.DLL
module in Delphi for register read/write. Then I developed another DLL
(called DSO.DLL) that groups all the medium level functions for
oscilloscope usage, for example:
DSO_CONFIGURE(filename:string , force:boolean) configure the ALTERA
with the filename.rbf file....
DSO_CHANNEL_SETUP(channel:integer....
DSO_BDT_SET(...)
DSO_ACQ_MODE(....)
DSO_ACQ_START(...)
All these functions can be used to develop a program directly in Visual
Basic, Visual C++, Delphi...
Hi,
Davide |
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Riscy
Guest
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| Posted:
Thu Dec 08, 2005 9:35 am Post subject:
Re: USB digital scope |
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I think it do need 12 bits, it give better range and resolution to do
some post calculation.
I done similar project but using ethernet and C# code. I used 18F4820
PIC because it has large RAM memory to enable single capture (1024
byte) and then transfer data later. I was using AD7708 which is low
frequnecy type ADC. The C# code interface tektronix TDS3014 scope and
aligent 33120 function generator which give me spectrum analyser
function (low frequnecy) and the code includes automated qualification
test setup. It worked very well. I learn a lot from OOP, .Net framework
and C# coding technique.
The point is that what I did find that 9 bit ADC from TDS3014 is
insufficient for spectrum analysis where amplitude varies with
frequnecy. I perfers 16 bits which is by I'm using AD7708 setup.
20MSPS versa 50MSPS is useful if you're working high frequnecy where
rise time measurement is important on certain application.
Trigger is important feature of the USB DOS. |
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David L. Jones
Guest
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| Posted:
Thu Dec 08, 2005 9:35 am Post subject:
Re: USB digital scope |
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Davide wrote:
| Quote: | Hi,
I used the memories inside the Altera. Each channel has a memory for 1K
sample, 512 samples in case of peak to peak sampling. The length of the
sweep is 512 samples. I implemented a random sampling using a
sub-interpolation for the trigger time. In this way is possible to
sample only repetitive signals using an equivalent time of 1ns. I don't
know how to post the schematic, I can send this directly to your
e-mail, if you want.
|
Nice design, but the small memory is the killer. Memory depth is by far
the #1 requirement for a DSO. 512 samples is incredibly limiting.
Check out the cleverscope for a nice USB scope that has 4MB of sample
memory (SDRAM). It trys to compete with the Agilent mixed signal scopes
and actually doesn't do too bad a job:
http://www.cleverscope.com/
The software (Labview) lets you do lots of clever custom programmable
maths directly on the waveforms too.
Dave :) |
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Davide
Guest
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| Posted:
Thu Dec 08, 2005 3:52 pm Post subject:
Re: USB digital scope |
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You're perfectly right. My goal was a 100$ instrument and not 1000$
instrument!!! The comparison is not from instruments in the same
"segment". |
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