Digital oscilloscope Project

[Skov]

oscilloscope schematics

>>That is not true, normally the input impedance of oscilloscopes is 1 MΩ || ~10-100 pF.

I don’t understand what are you talking about.
The question was why the oscilloscope has limitation +-5V for input voltage.
Do you mean that you know the oscilloscope with such limitation and input
impedance >1K ?
There are exist a lot of kinds of oscilloscope in the world.
I know oscilloscopes with 100K,1M. My own oscilloscope has 50 Ohm input impedance.
His bandwidth is 500MHz. The low input impedance allows to decrease the distortion of signal
in communication cable. Usually the wideband oscilloscopes have low input impedance.
See, for example,
**broken link removed**
As a rule, some probes are added to such oscilloscopes for investigation of high voltage signals.
I think that all DSO are low impedanse oscilloscopes in principle,
becouse the limitation for input voltage of ADC is rather low.
A probe is just incorporated in the scheme of the high input impedance DSO.

 

[martingn]

ep1c3 pcb

Hi all,

Doesn't the input impedance of the scope directly related with the application? I mean, if you dont want to load the circuit, you should have to use high Z.
If you are in a matched line (like comms equipment) you should use a determinated Z (like 50 ohms).

I think that 1K RAm its enough for a "home build" scope taking into account all the benefits... less components, price, PCB complexity, speed.
There are bigger FPGA with greater RAM capacity.

Monnoliv,
It's true, you have to program the FPGA each time it's power up (at least this model). Anyway a DSO should have to be implemented with a uC (communications ,I/O selection, leds, etc..) You can use that uC to program the FPGA each time. I don't have any schematic but I almost sure that FPGA datasheet should have to explain any way to do that.

There is another intresting tip that is to add a slow but precise DAC into the input stage to correct bias drift and support auto calibration...


If you are planning to use Eagle soft for PCB may be we can share some work.


Best Regards,

 

[ME]

cy7c199 example

... a DSO should have to be implemented with a uC (communications ,I/O selection, leds, etc..) You can use that uC to program the FPGA each time. ...

Why not handle communications, I/O selection, leds, etc. from the FPGA instead of adding a µC? It should be possible to program all these functions into an FPGA. If you want, you can even get a complete µC IP-core to implement in a part of the FPGA and then program it as a normal µC.

 

[martingn]

digital scope low frequency with dspic30f

ME,

You are absolutelly right.
I dont have too much experience, zero infact, programming FPGA, but it looks simpliest to implement in a uC. May be Im wrong.

Best regards,
MArtin

 

[ME]

fpga digital oscilloscope

martingn, Concerning the ACEX 1K EP1KX0, if I've well understand the strucure of this device, it must be configured at each power on. How doing this with embedded processor, EEPROM? Do you have a schematics ?

Read this link about FPGA configuration:
https://www.fpga4fun.com/configuration.html

FPGA configuration
An FPGA can be into 2 states: "configuration mode" or "user mode". When the FPGA wakes up after power-up, it is in configuration mode, sitting idle with all its outputs inactive. You need to configure it.

Configuring an FPGA means downloading a stream of 0's and 1's into it through some special pins. Once the FPGA is configured, it goes into "user-mode" and becomes active, performing accordingly to your programmed "logic function".

There are 3 classical ways to configure your FPGA:
You use a cable from your PC to the FPGA, and run a software on your PC.
You use a microcontroller on your board, with an adequate firmware.
You use a special PROM on your board, connected to the FPGA, that configures it automatically at power-up (FPGA vendors have such special PROMs in their catalogs)
...

Altera Configuration Devices
https://www.altera.com/products/devices/config/cfg-index.html

 

[divan]

circuit mount old oscilloscope

In case you'll use PC as scope display this is not so important if us this one for FPGA loading ( even every time at wake up) .
Anoter case if you want a stand-alone device , but in this case need to think about additional module for LCD display first and about FPGA loader as side dish.
Anycase , i'd like fpga4fun project, let's make it as standalone, for example with 240x160 or 320x240 lcd pic or avr based. M.b. AVR is slightly better , because have C compiler, IDE and LCD drivers for free ( and i already have it

 

[eltonjohn]

wxwidgets oscilloscope

Hi Guys ..stand alone ..hein !
Well the Gameboy has a 240x160 .32k colors display . is very cheap around $90 brand new .. can be found for $25 used .. graphic modes used DMA .. and can be very fast .. on top is very easy ,,very easy to adapt an interface ..is just a matter to map to the memory espace space avalaible for the ROM cartridge .. and there are nice tools to quickly make a nice graphical interface .. see .. VISUAL HAM ..(! free) !

 

[ME]

oscilloscope dso-220 software

Hi Guys ..stand alone ..hein !
Well the Gameboy has a 240x160 .32k colors display . is very cheap around $90 brand new .. can be found for $25 used .. graphic modes used DMA .. and can be very fast .. on top is very easy ,,very easy to adapt an interface ..is just a matter to map to the memory espace space avalaible for the ROM cartridge .. and there are nice tools to quickly make a nice graphical interface .. see .. VISUAL HAM ..(! free) !

I have already uploaded an article from Elektor with a Gameboy based DSO:
GBDSO - Gameboy Digital Sampling Oscilloscope
Convert a Nintendo games console into a portable oscilloscope

 

[monnoliv]

digital oscilloscope scheme

Thank you for your comments,

Thank ME for the link.
martingn, in fact I use Protel DXP Educationnal licence, then it will be difficult to exchange schematics. But anyway thanks for your tip, I'm thinking to take this kind of solution:

- inputs stage and ADC unchanged.
- analog triggering deleted
- ACEX1K10 or 30 for the logic, FIFO and triggering (+boot, have to see)
- one (cheap) µC
- USB controler + supply + insulation unchanged.

I think that this solution is the cheapest (with the same performance). I'm not seeking the best schematics, only the cheaper one, then accessible for a lot of hobbyist.
If anyone has a cheaper idea ?

Regards,

 

[ME]

how to make a digital oscilloscope

Thank you for your comments,

Thank ME for the link.
martingn, in fact I use P*otel DXP Educationnal licence, then it will be difficult to exchange schematics. But anyway thanks for your tip, I'm thinking to take this kind of solution:

- inputs stage and ADC unchanged.
- analog triggering deleted
- ACEX1K10 or 30 for the logic, FIFO and triggering (+boot, have to see)
- one (cheap) µC
- USB controler + supply + insulation unchanged.

I think that this solution is the cheapest (with the same performance). I'm not seeking the best schematics, only the cheaper one, then accessible for a lot of hobbyist.
If anyone has a cheaper idea ?

Regards,

I would recommend you start by translating your web site to English, this way we can all understnad it and make our contributions and comments to your project.

I also have Protel DXP.

I would reccomend using an Atmel AVR µC for controlling.
This is a very fast flash based 8-bit MCU, very easy to use. I have C compiler and development kit for this µC. The member 'divan' also suggested using this µC in an earlier post and I can reccomend it, it is quite cheap too. And there is a very nice AVR board like this one: www.avrfreaks.com
The AVR is so fast that there have been made a 1.5 Mbps firmware USB interface for it: http://www.cesko.host.sk/IgorPlugUSB/IgorPlug-USB%20(AVR)_eng.htm
But 1.5 Mbps is probably too slow, so you will need a hardware USB, FireWire and/or LAN interface to the PC.

You should also consider using a FPGA for controlling and USB interface instead of using an µC.
An FPGA can run much faster than a traditional µC. And you can build in your own customized digital peripheals in an FPGA.

 

[martingn]

fpga dso

Hi good people,

Finally it looks like we are in the way to agree into a final project component selection. Good!

Eagle is free. Anyways I'll download Protel DXP if anybody is going to use it. (by the way, protel always offers Altium for download. where could be DXP Educ. available? )
May be DAC to calibrate input is too much, but at least you will need a pot!
Again, I not an expert, but, is this little FPGA (EP1K10) enought to do all? USB, IO Control, RAM ...

Best regards,

MArtin

 

[divan]

avr oscilloscope

i'm ready to make PCB trace routing if someone can provide schematic in any format ( scaned draft sketch is acceptable as well if good resolution).
I can use Eagle-lite (80x100 mm PCB, 2 layers) and PCAD (full). Protel is possible, but not so comfortable for me.
Eagle PCB will be eagle forever , i don't know any tool for migration.
Offers to PM., plz

 

[simce]

18f452 oscilloscope

A kind of translation from France and Italian to english can be done using altavista's translator. Use translation link on www.altavista.com.

 

[ME]

+ads831 +oscilloscope

A kind of translation from France and Italian to english can be done using altavista's translator. Use translation link on www.altavista.com.

Thanks, I know about Bablefish, but the translation is not always accurate and some words are translated wrong, other words are not translated at all.
It is often enough to get the big pcture, but translation by the one who wrote it would be much better and more precise.
I he would like to keep the French version he could make the web site in two languages and make a little English and a French/Belgium flag to hit to change the language. Somebody here could probably help with translations if neeeded.

I know I often tend to stay away of projects and web site written in a language I don't understand and find a similar project in a language I understand.
Only if I can't find anything at all about the subject in English I am forced to use Bablefish, Poltran etc. but it is never the same.
I don't like to reuse source code with comments I can't understand either.
Often you use as long time translating the comments and figure out what the code does as you would have used on making the code yourself.

If I should publish a project at a website I would prefer to do it in English rather than my own language, because almost everyone at the internet understands English, while not so many undersatnds my own language. I would get much more feedback if the site and project was made in English.

I don't think many of the readers here understand French, but I'm sure everyone here understands English. Most pepole surfing the internet can understand at least some English. English is the universal language of the internet (and the real world). I know more people peak either Chineese or Spanish as their main language than for example English. But many of those surfing the internet also understands English.

 

[simce]

dso front end attenuator

ME.. Yes you are right about quality of translation. And as you said these automated translators can help you get an idea what text is about, but sometimes this is enough. Anyhow the best is if the texst is written in english by the autor or translated by human and not machine.

I think that very usefull thing to do is to put LCD display (with MCU that will interface with DSO) as option. This way it won't be needed displaying unit (PC or so). It can even be battery powered and hand held. I think that resolution of about 240x120 pixels is enough. There are many graphic displays. I found one interesting, manufactured by Ampire (**broken link removed**).

 

[ME]

+jyetech +oscilloscope +source code

Since I have a laptop I don't really need a LCD display.
I would like it to interface withe either FireWire, PC Card, LAN or USB. My USB is only 12 Mbps, no USB2.0, so right now I would prefer a FireWire interface (400 Mbps) or maybe LAN.
I don't know if it would be better/easier to interface it to PC Card?
My next laptop will have USB2.0 (480 Mbps) too, so I can use this interface too when I buy my next laptop, probably in a year or so.
Otherwise I can just buy a USB2.0 inteface for my PC Card slot.
If it is easier to use FireWire than USB2.0 then this more intelligent interface should be considered too, but I got the impression that the more simple and not so intelligent USB2.0 is easier to use than FireWire.
FireWire can reserve the needed bandwidth for a device like a DSO or digital videocamera. USB can't reserve bandwidth for a device, so if you have more devices connected to USB at the same time you can get in trouble.
This is the main reason why all digital videocameras (which requires a lot of bandwidht in real time transfers) uses FireWire.


Here is a rather new commercial oscillospoe introduced last year, which uses USB2.0 for sampling frequency up to 100 MHz on both channels:
https://www.tiepie.nl/pages/uk/hscope3.html
So I guess USB2.0 will be good enough for the purpose and USB2.0 is standard on all new computers.

Maybe it would be possible to reuse or at least get inspiration from some of the Software and DLL's for this oscilloscope:
https://www.tiepie.nl/pages/uk/softdown_hs3.html
Software and programmer's manual are also available

Free source code are aviable from some of the older models:
https://www.tiepie.nl/pages/uk/softdownsrc.html

 

[monnoliv]

schematic of digital oscilloscope

The AVR is so fast that there have been made a 1.5 Mbps firmware USB interface for it: http://www.cesko.host.sk/IgorPlugUSB/IgorPlug-USB%20(AVR)_eng.htm

Great site !

Here is a rather new commercial oscillospoe introduced last year, which uses USB2.0 for sampling frequency up to 100 MHz on both channels:
https://www.tiepie.nl/pages/uk/hscope3.html
So I guess USB2.0 will be good enough for the purpose and USB2.0 is standard on all new computers

I'm not sure tiepie uses High-Speed because it's writen "USB 2.0 and USB 1.1" in the specs. Anyone has the price of the 100MHz/8bits version ?

Anyway, full-speed is good enough if you have 1Kbyte/channel to transfert

May be DAC to calibrate input is too much, but at least you will need a pot!

Where in the schematics I've to put the pot? Can you put a small schematic ?

Again, I not an expert, but, is this little FPGA (EP1K10) enought to do all? USB, IO Control, RAM ...

I agree with you, I'm not an fpga expert too but putting all in an EP1K30 (too keep the DSO cheap) is optimistic for me. And then, what about the necessary insulation between PC and DSO ?

Anyway to continue the design, what is your opignion about the CYPRESS USB 8051 type processor (EZ-USB, 6.9 €) ? Cheap but the opto-insulation has to be done after the device...

Concerning translation, OK I will do it in two langages for the next revision of the DSO.

Of course, thank you all of you for discussions and advices.

Regards,

 

[abs]

pc scope schematic

Why not use LABVIEW for software development.I can see most of our oscillospoe use spicial software,which could not be Update easily. :roll:

 

[simce]

max1180 oscilloscop

ME.. I have laptop too with 100MHz LAN and USB 2.0. But. Very often i don't need laptop, and hand held oscilloscope is that i need (especially when i have to work out of office on the field). I think that most of members reading this topic are agreeing with me.

As i said DSO can have PC communication port and interface to LCD or MCU that will make communication between DSO and LCD display.
This way you won't need any interface that will make galvanic isolation between your PC and DSO. I think that isolation is essential if you are planning to use DSO on field where high voltages are present.
Regards,
Simce

 

[ME]

mindbend.ro/eoscope/download/eoscope_1.2.zip

Here is a rather new commercial oscillospoe introduced last year, which uses USB2.0 for sampling frequency up to 100 MHz on both channels:
http://www.tiepie.nl/pages/uk/hscope3.html
So I guess USB2.0 will be good enough for the purpose and USB2.0 is standard on all new computers.

I'm not sure tiepie uses High-Speed because it's writen "USB 2.0 and USB 1.1" in the specs. Anyone has the price of the 100MHz/8bits version ?

Anyway, full-speed is good enough if you have 1Kbyte/channel to transfer

If 1kByte/channel is enough the 'IgorPlug' AVR firmware should be fast enough with 1.5 Mbps.

Price for Hanyscope from a Belgium (your coutry) dealer:
http://www.rato.be/nl/pdf/tiepie_prijslijst_10-06-2003.pdf

List of all dealers can be found here: http://www.tiepie.nl/pages/uk/dealers.html

Again, I not an expert, but, is this little FPGA (EP1K10) enought to do all? USB, IO Control, RAM ...

I agree with you, I'm not an fpga expert too but putting all in an EP1K30 (too keep the DSO cheap) is optimistic for me. And then, what about the necessary insulation between PC and DSO ?

Are you sure insulation is necessary?

Connected to the fast USB 2.0, the Handyscope-HS3 doesn't require an external power supply, therefor the Handyscope 2 easily complies to "Plug in and measure".

The Hanyscope 3 is powered from the USB port, which indicates it is not galvanic insulated unless they use an transformer insulated switched mode power supply for example with a flyback transformer. But maybe that is what they do.
Galvanic insulation would be nice when working with high voltages.
Maybe it is possible to find a galvanic insulation IC for USB?

Anyway to continue the design, what is your opignion about the CYPRESS USB 8051 type processor (EZ-USB, 6.9 €) ? Cheap but the opto-insulation has to be done after the device...

Cypress looks ok, but if 1.5 Mbps USB is enough, why not use AVR, you can get it even cheaper? Maybe the AVR would be too slow if it has to handle a lot of other tasks besides USB, I'm not sure.
Atmel also makes two 8051 based Flash MCU's: AT89C5131/5132. www.atmel.com/dyn/products/devices.asp?family_id=655#1399
Silicon Laboratories (formerly Cygnal) also makes two 8051 based Flash MCU's: C8051F320/321 www.silabs.com/products/microcontroller/usb.asp
Cypress has the lowest amount of Flash of the three vendors.

The prices for Atmel's, Cypress' and Silicon Laboratories' 8051 based USB Flash MCU's are about the same at digikey:
Cypress EZ-USB: www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=267862&Site=US&Cat=31589495
Atmel AT89C5131: www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=267841&Site=US&Cat=33424497
Silicon Laboratories C8051F320: www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=268316&Site=US&Cat=31589495

Here is a list of almost all USB chip vendors: www.lvr.com/usbchips.htm


But why not implement the USB interface into FPGA?
And why do you want to use a MCU at all? Why not implement it all into a FPGA when you are going to use a FPGA anyway? All you can do with a MCU you can also do with a FPGA and at much higher speeds.