Digital oscilloscope Project

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davorin

Joined: 07 Jun 2003
Posts: 1396
Helped: 8

07 Jun 2004 19:33 oscilloscope usb project

Regarding DSO? No.

Only made a 2-layer PCB with EP1C3 running original PacMan game (o;

martingn

Joined: 30 Mar 2004
Posts: 40

07 Jun 2004 20:24 how to build a digital oscilloscope

Hi all,

I would suggest develop a little "prototype" first.
FPGA core, PC based, RS-232 comms, downolad cfg with cable, no uC, single channel, single board.

I will help us to learn FPGA stuff in an easy board.

Suggestions?

regards,
MArtin

davorin

Joined: 07 Jun 2003
Posts: 1396
Helped: 8

07 Jun 2004 20:35 pdamusician.com project

I would rather suggest using an old VGA monitor hooked up to FPGA...there are tons of application notes about this..and it is only a few lines of code.

This way you save time on spending writing code on PC software (or get started with it ;o). Also the design is then totally indepedant.

And also for a start do not use an ADC first hand...capture raw digital inputs as in a logic analyzer and direct output to VGA monitor...or use those fancy in-circuit ChipScope/whatever-it-is-called to see how things work internally.

Start at the core of your problem..do not waste writing Visual-Whatever-crap-language code on Windows PCs (o;

martingn

Joined: 30 Mar 2004
Posts: 40

07 Jun 2004 20:40 adc microcontroller oscillo

Hi ME,

I dont know what LabVIEW is.
Lets keep all simple for prototype. If this soft helps to do it, Welcome.

I'm thinking about the prototype specifications. What tasks should the "proto" at least perform?

regards,
MArtin

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

07 Jun 2004 20:43 wireless oscilloscope

martingn wrote:

Sound like a good idea Martin

What about PC software?
Should it be made in LabVIEW or should it be a stand-alone software?
Maybe it is easiests to make it in LabVIEW first?
Or maybe Davorin's suggestion is the best.

I think a lot of the hardware in BitScope 300 can be reused, for example some of the analog circuits, instead of inventing the wheel again.
There is hardware schematics at http://www.bitscope.com/design/

I was wondering if there is any particulary reason why only Altera is mentioned as choiche for the FPGA / CPLD? Is it cheaper than the other big company Xilinx, or is it because it is possible to order free samples or is it a 3rd reason?

davorin

Joined: 07 Jun 2003
Posts: 1396
Helped: 8

07 Jun 2004 20:44 project pc oscilloscope

1. Do you need external fast SRAM? Mostly it is enough to use internal faster RAM blocks in FPGA...use phase-shifted clock to double the rate to 500MSamples/sec or more.

2. Lot´s of pin headers (o; Making it possible to hook-up easily any ADC you like.

3. VGA/PS2/RS232 port and of course power supply (o;

4. ISP (JTAG) connector or serial config eeprom

For a start quite enough...or if you can get a hand on a cheap FPGA eval board..do it!

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

07 Jun 2004 20:54 oscilloscope analog front-end schematic

martingn wrote:

Hi ME,

I dont know what LabVIEW is.
Lets keep all simple for prototype. If this soft helps to do it, Welcome

LabVIEW is a great EDA tool from National Instruments.
It reminds a bit similar of Simulink for Matlab, if you know Simulink?
But LabVIEW is more graphical oriented and advanced.
It is a kind of graphical programming tool for measurement and control.
LabVIEW is even embedded in some new fancy top stand alone DSOs.

Look here: http://www.ni.com/labview/

LabVIEW for Dummiees: http://www.iit.edu/~labview/Dummies.html

Google
AdSense
Google Adsense

07 Jun 2004 20:54 Ads

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

07 Jun 2004 20:59 fpga oscilloscope high speed 16 channel

davorin wrote:

For a start quite enough...or if you can get a hand on a cheap FPGA eval board..do it!

Here is a big list of FPGA eval boards from different vendors and 3rd party companies, prices are listed too.
The list is updated regulary (Last updated 06/04/2004)
www.fpga-faq.com/FPGA_Boards.shtml

See Also:
Die FPGA-Kochecke: www.aufzu.de/FPGA/boards.html
Another list of boards: http://dmoz.org/Computers/Hardware/Programmable_Logic/FPGA/Boards/
Xilinx's list of boards: www.xilinx.com/xlnx/xil_prodcat_product.jsp?title=protoboards_protoboards_page
Altera's list of boards: www.altera.com/products/devkits/kit-dev_platforms.jsp
Altera's list of Partner Development Kits: www.altera.com/products/devkits/kit-dev_platforms_partner.html
Optimagic's list of boards: www.optimagic.com/boards.html

Last edited by ME on 07 Jun 2004 21:03; edited 1 time in total

martingn

Joined: 30 Mar 2004
Posts: 40

07 Jun 2004 21:01 fltk oscilloscope

Davorin,

I think that use a VGA connected to the DSO will not be practical for the following reasons:
-not everybody has 2 monitors.
-the final project will be a handheld.
I think that a capture of the sampled data will be easy to be managed in a PC. (it just to check not final interface)

Not to use an ADC at first step could be a good idea. May be we can implement 2 boards. FPGA board and Input board.

Me,

I dont have acces to samples here in my country and the only one that I could find here is altera EP1K10TC144. I would suggest to use that if everybody agree.
Altera ACEX 1K starting at U$10 , Cyclone starting at U$20 (arrow)
Personally I never read any info of Xilinx FPGA.

regards,
MArtin

davorin

Joined: 07 Jun 2003
Posts: 1396
Helped: 8

07 Jun 2004 21:13 oscilloscope front-end

martingn wrote:

I think that use a VGA connected to the DSO will not be practical for the following reasons:
-not everybody has 2 monitors.
-the final project will be a handheld.
I think that a capture of the sampled data will be easy to be managed in a PC. (it just to check not final interface)

Who needs 2 monitors? (o;

The question was for a "quick start"...and the easiest way to visualize something from FPGA is via VGA...doesn't matter if the final design supports an external monitor or uses a link to PC where someone spends endless hours to write some OS-centric capture software (o;

Hmm US$20 is quite expensive...I got EP1C3T100 samples for free (o;
If you can wait some few months you can grab those Spartan-3 devices from Xilinx...

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

07 Jun 2004 21:19 qtdso sreen resolution

I only have a laptop, and laptops have no VGA inputs, only an output Confused

What about connecting it to a normal TV through the CVBS video input?
It is the same input as in a CGA monitor.
Most people have a TV.

I have an old CGA monitor too, with both CVBS and RGB input.

martingn

Joined: 30 Mar 2004
Posts: 40

07 Jun 2004 21:36 oscilloscope digital project

Davorin,

I think that develop the "proto" switching the only VGA between DSO and the PC could be very exhausting.
By the other hand, we dont need to write PC code. Couldnt we just log sampled data in a file and see it in Excel? Its just for test not for final use.

Most vendors doesnt send samples to my country Sad

Anyway, wait a few months could be very boring.
I think that the best option is to choose a cheap FPGA to meet the design spec , and that everyone could easylly obtain.

We need to decide what FPGA to use.

regards,
MArtin

monnoliv

Joined: 09 Mar 2004
Posts: 104
Helped: 3
Location: Belgium

07 Jun 2004 23:14 self-made oscillograph scheme lcd

Hi all,

Just this post to invite you for seeing the second revision of the DSO with english translation !!!
I invite you to make lot of suggestions. I tried to keep the two options on the way (PC linked and handheld).
Here is the link:
http://164.15.88.56/Page_Projet2.php

See you,

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

07 Jun 2004 23:41 oscilloscope on a chip

monnoliv wrote:

Thanks for the quick translation :spoko:

There is a wrong link at page two: http://164.15.88.56/Page_Projet2_p2.php

The link called 'next page' points to the page you are already on instead of page 3.
It is only if you click at the English text, if you click at the french text it is ok. For some reason it is divided in two different links instead of just on long link with text in both French and English, just like the 'previous page' link is.

martingn

Joined: 30 Mar 2004
Posts: 40

08 Jun 2004 1:06 digital oscilloscope diy

Monnoliv,

I call that working fast!
Would you consider a cheaper FPGA?
What do you think about the simple "proto"?

regards,
MArtin

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

08 Jun 2004 1:10 digital oscilloscope (dso) scope parts list

monnoliv wrote:

I invite you to make lot of suggestions.

I have a suggestion for an improvement of the USB interface.
I think you should replace the 2nd generation USB chip, FTDI FT232BM with the brand new 3rd generation USB chip FTDI FT2232C Dual USB UART / FIFO.

Quote:

INTRODUCTION
The FT2232C is the 3rd generation of FTDI’s popular USB UART / FIFO I.C. family. This device features two Multi-Purpose UART / FIFO controllers which can be configured individually in several different modes. As well as a UART interface, FIFO interface and Bit-Bang IO modes of the 2nd generation FT232BM and FT245BM devices, the FT2232C offers a variety of additional new modes of operation, including a Multi-Protocol Synchronous Serial Engine interface which is designed specifically for synchronous serial protocols such as JTAG and SPI bus.

FT2232C has two i individually configurable UART / FIFO channels, while FT232BM only had a single UART channel.
This means that you can configure channel A of the chip to JTAG interface, while channel B is configured for UART.
The you can use channel B as you do now for connection to the MCU, while channel A can be connected to the FPGA JTAG interface.

Then you don't need any external JTAG dongle Very Happy

When using the DSO in the 'PC Version' without 'configuration memory', then you can load the configuration program to the FPGA directly from the PC via the FT2232C JTAG interface, without using the FT2232C UART interface thru the MCU. This will also make the configuration program load faster and probably much simpler programming on both PC and MCU side.
You might not even need a MCU at all if you can progran the FPGA from JTAG. Then you can júst receive the measurement data directl from the FPGA connected directly to the FT2232C UART.
This could save some money and programming and you need fever parts for the 'PC Version' DSO.

The JTAG interface can be made optically isolated like your UART port already is.

If you use a MCU with JTAG interface, like the ATmega 16, 32, 64 or 128 AVRs, then you can also connect this to JTAG for on-chip-debugging.

monnoliv

Joined: 09 Mar 2004
Posts: 104
Helped: 3
Location: Belgium

08 Jun 2004 13:27 digital oscilloscope sematic

Quote:

The link called 'next page' points to the page you are already on instead of page 3.
It is only if you click at the English text, if you click at the french text it is ok. For some reason it is divided in two different links instead of just on long link with text in both French and English, just like the 'previous page' link is.

It's ok now, thanks.

Quote:

Would you consider a cheaper FPGA?
What do you think about the simple "proto"?

We can use a cheaper FPGA (the EP1K10) but then we only have 512 x 8 (bits) x 2 (channels) of FIFO memory instead of 1024 x 8 x 2 (the EP1K30, with qu(at)rtus II I've already made a check for the available memory to store the samples, I used the FIFO megafunction). I checked (roughtly) the pinout of the EP1K10, EP1K30 and EP1K50 devices (TQFP144 package) and they have the same pin assigment. Then one can choose later the final device.
About a prototype, I've no Idea, will the prototype be more simpler than the scope logic board ? You have to solder a TQFP 144 package, then you have to make a PCB, no? Why not make a PCB with a few more components and have the skeleton of the scope ?

ME, the FT2232C is very interresting indeed. Ok, I'll check for implementation.

Regards,

monnoliv

Joined: 09 Mar 2004
Posts: 104
Helped: 3
Location: Belgium

08 Jun 2004 13:31 oscilloscope analog front-end

I forgot to ask you all, what is your programming enviromnent to write PC code? I use Cpp builder 4.
bye,

se06745

Joined: 03 Jun 2004
Posts: 26

08 Jun 2004 14:52 pc scope project

Hi!

1) The analog hardware of bitscope DSO is important in order to calibrate the equip. Is very good!!!

2) Using a direct VGA interface is "easy" for a limited code to show a signal only. With PC interface you can calculate easyly and print a lot of information about de siganl like a freq, Vp, FFT....

3) I think that you don´t need a ultra fast PC interface USB. You need to get de High Freq signal. The monitor not print 50.000.000 signal variations at 1 second. You capture the 20MHz siganl (for example) and print it. A simple RS-232 o USB 1.0 is enought.

4) To do a fast sample and hold you need a FPGA (with internal memory) or a FIFO with CPLD. ¿Do you know VHDL or Verilog? Wink

5) Your input Z = 1Mohm (minimum) and 20pF (more or less) for especific applications you can use Z = 50 or 70 ohms (to match impedances)

6) The onlyu problam that I have is accept a 100v or more input voltage. If I use digital switches to divide 1:10 or 1:50 .... these switch accept +-5v imput. (only solution is use a mechanical swith resistor divisor)

Thanks for all!!!

Crying or Very sad

pisoiu

Joined: 31 Dec 2002
Posts: 729
Helped: 24
Location: Romania

08 Jun 2004 16:03 homemade dso

se06745 wrote:

Hi!

6) The onlyu problam that I have is accept a 100v or more input voltage. If I use digital switches to divide 1:10 or 1:50 .... these switch accept +-5v imput. (only solution is use a mechanical swith resistor divisor)

Thanks for all!!!

Well...not entirely true. You can use photomos relays. Some models accept 400V, and if you take a look at tektronix mainboard picture I previously posted in this topic you'll see some photomos relays there. They are used to switch ac/dc modes at input. Also, there are some fet in opamp buffers from analog devices which have protection diodes at input, and with a limiting resistor at input they can sustain voltages of hundreds (ad8065).
Also, somewhere upwards it was stated that usb powered PC based DSO cannot be isolated from PC ground. Well..here is an idea: a small isolated buck-boost smps can deliver power for analogic circuits and a FT232/245BM which is connected on a side at USB can be connected on the other side to uC/FPGA with optocouplers, thus achieving desired isolation.

/pisoiu

martingn

Joined: 30 Mar 2004
Posts: 40

08 Jun 2004 16:06 usb scope avr

Hi all,

I think 512x8x2 its ok for a handheld DSO.

regards,
MArtin

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

08 Jun 2004 18:38 a26 lambo student liu se

monnoliv wrote:

About a prototype, I've no Idea, will the prototype be more simpler than the scope logic board ? You have to solder a TQFP 144 package, then you have to make a PCB, no? Why not make a PCB with a few more components and have the skeleton of the scope ?

You should only make a protoype if you already have an evalution kit with the FPGA mounted.
Otherwise you should just make a complete PCB layout, you don't have to mount all components to begin with.

monnoliv wrote:

ME, the FT2232C is very interresting indeed. Ok, I'll check for implementation.

It should be easy to upgrade to the new 3rd generation FTDI chip, same housing and sorrounding components.

monnoliv wrote:

Quote:

Would you consider a cheaper FPGA?
What do you think about the simple "proto"?

The only two Altera FPGAs I could find for sale to private persons in my country is EP1K30TC144-3 and EP1K50TC144-3 at www.farnell.com.
They are very expensive:
EP1K30TC144-3 costs € 45 ($ 56) incl. VAT, excl. shipment
EP1K50TC144-3 costs € 56 ($ 6 Cool

incl. VAT, excl. shipment

Farnell haven't got EP1K10.

Does anyone know of a cheaper place to buy theese FPGAs within the European Union Question

Where do you buy the Altera FPGA monnoliv and how much do you have to pay for the ACEX's? Or do you get it thru your company for free?

monnoliv

Joined: 09 Mar 2004
Posts: 104
Helped: 3
Location: Belgium

08 Jun 2004 20:46 pc oscillascope schamatic diagram

Hi all,
I'll implement soon (now my website is down and I don't know why) the FT2232C from FTDI. One channel (A) will serve as a JTAG connector for FPGA, the other channel (B) will serve for the command (receive) datas for (from) FPGA (this channel B will be configured as a fast sync serial, and the decoder will be a small part of FPGA), then no more need of a µC !!! (thanks ME) at least for the PC version. Then I'll remove one connector, the remaining one will serve for the handheld version (display - keyboard - µC and battery).

Quote:

1) The analog hardware of bitscope DSO is important in order to calibrate the equip. Is very good!!!

Ok, I'll check to implement the calibration.

Quote:

I think 512x8x2 its ok for a handheld DSO.

No pb, let's configure this device with all the function to see if it works

Quote:

Does anyone know of a cheaper place to buy theese FPGAs within the European Union
Where do you buy the @ltera FPGA monnoliv and how much do you have to pay for the ACEX's? Or do you get it thru your company for free?

EBV:
EP1K10TC144-3 Price: 11.47 MOQ: 60
EP1K10TC144-2 Price: 15.57 MOQ: 60

EP1K30TC144-3 Price: 16.39 MOQ: 60
EP1K30TC144-2 Price: 22.13 MOQ: 60

(MOQ: Minimum Order Quantity)

Arrow has also the pieces but it's more expensive (no MOQ) as I saw.

It's not sure but perhaps I'll be able to buy 60 pieces and sell one piece at a time for each guy who is interrested (+shipment). The same for other pieces that are difficult to find in small quantity.

See you,

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

08 Jun 2004 21:30 scope avr

monnoliv wrote:

Quote:

Sounds like a good idea.
It's always much cheaper to buy components in big quantities than just buying a single component.
Maybe you should order a little stock of PCBs for the project when it is finished to sell with the special components. It's much cheaper to get the PCBs made in one big order than 50 seperate orders.
You can even start a little webshop with Paypal payment or something like that if the project becomes a succes.

I don't think you can buy at the distibutors Arrow or EBV as a private person.
I know Arrow USA has a web shop, but the shipment and handling costs for international orders are redicolous high and on top of that you have to pay import taxes and VAT. The FPGA will end up being more expensive than a complete handheld scope.

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

08 Jun 2004 21:59 make pcb avr multikitb

I think you should add 8-, 16- or 32- bit Logic-analyzer functionality to the DSO too.
The connections to the FPGA could be made via a DSUB connector or a Centronics connector.
There is something similar at the Bitscope.

------------------------------------------------------------

Check out this new ADVANCED PERSONAL SCOPE 240MS/s:
http://www.velleman.be

monnoliv

Joined: 09 Mar 2004
Posts: 104
Helped: 3
Location: Belgium

08 Jun 2004 23:02 project digital oscilloscope

Quote:

I think you should add 8-, 16- or 32- bit Logic-analyzer functionality to the DSO too.
The connections to the FPGA could be made via a DSUB connector or a Centronics connector.

Good idea, but any suggestion for the protection of FPGA inputs ?

Quote:

Check out this new ADVANCED PERSONAL SCOPE 240MS/s:
http://www.velleman.be

It's in fact a 2x 60MS/s

ME

Joined: 14 Mar 2002
Posts: 1523
Helped: 13

08 Jun 2004 23:14 dso oscilloscope project

monnoliv wrote:

Quote:

I think you should add 8-, 16- or 32- bit Logic-analyzer functionality to the DSO too.
The connections to the FPGA could be made via a DSUB connector or a Centronics connector.

Good idea, but any suggestion for the protection of FPGA inputs ?

Here's the BitScope schematic for Logic Analyzer input:
http://www.bitscope.com/design/hardware/pdf/Bs11-3.PDF

74HC573 are connected between inputs and CPLD.
10 kohm - 1Mohm resistor termination network are also connected to all inputs. Value depends of if the Active POD is connected or not.
With this desing you will only damage the 74HC573 instead of the CPLD / FPGA.
You could aslo connect transorb / transient voltage suppression diodes to 5V and GND at the inputs.
Here is a list of Transient Voltage Suppressors:
http://www.newark.com/products/browse/7_1_18_1.html

I think you should make every 2nd pin in the socket GND to improve shielding of the flatcable connected.
You can also use an Flatcable-connector instead of DSUB if you prefer.
But DSUB are probably easier to mount in a cabinet and more roboust.

Check out this application note from Xilinx too, this is probably the best way to design the input stage and protection:
http://www.xilinx.com/bvdocs/appnotes/xapp368.pdf
It's about how to design a Handheld Pocket Logic Analyzer.

Quote:

Input Protection: Responsible for protecting the input comparator from excess voltage and
current. This protection scheme usually consists of a current-limiting resistor and a dual mode
transorb diode. This input protection circuit will have limits to its protection abilities. The user
should be careful not to apply an input voltage level that exceeds these limits. Input protection
was not implemented in this prototype.

se06745

Joined: 03 Jun 2004
Posts: 26

09 Jun 2004 7:36 dso 220

Hi!

The photomos relays, it's true I didn't remember!! Thank's. Cool

But what is the frequency response of photomos relays. The maximum frequency input signal???

Best Regards!

pisoiu

Joined: 31 Dec 2002
Posts: 729
Helped: 24
Location: Romania

09 Jun 2004 7:55 how make digital oscilloscope

se06745 wrote:

Hi!

The photomos relays, it's true I didn't remember!! Thank's. Cool

But what is the frequency response of photomos relays. The maximum frequency input signal???

Best Regards!

Tektronix TDS2014 use NAIS AQY214 as AC/DC input switch, and it have 100MHz input bandwidth.

/pisoiu

Ace-X

Joined: 25 Jan 2002
Posts: 590
Helped: 26

09 Jun 2004 10:19 digital oscilloscope fpga

Why not to use ready development board? For example, many times discussed here Virtex2Pro board from Memec. 149$, V2Pro4 FPGA (more than 500 Kbits of internal BlockRAM), embedded PowerPC processor, USB and RS232 ports. It will allow to forget about all this troubles with PCB and soldering and concentrate on real DSO design.

Ace-X.