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edy
Joined: 26 Jan 2006
Posts: 2
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 21 Feb 2006 1:41 TRIGGERING SYSTEM QUESTION |
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Hi guys,
Im currently working on a digital oscilloscope with FPGA for a senior desing project. I was wondering if u guys have any suggestions on how to implement the triggering system. How to do the slope detection, and trigger level.
Can i use a differentiator and comparator. differentiate the input signal, and check if the: output is positive = + slope, output is negative = -slope, output is zero = resonant frequency? what about the triggering level?
any suggestion will help
thankz
ed
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thushi
Joined: 23 Feb 2006
Posts: 11
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| 23 Feb 2006 10:20 Re: Digital oscilloscope Project |
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Hi,
Please have a look at www.picoscope.com and get a free demo CD. Where you can get more information.
| ze_dib wrote: |
Hi
I 'm studying possibilities to make a digital oscilloscope for PC, with onboard RAM to memorize samples.
I have several questions :
=> Wich bus is the easier to use (hard and driver for linux/windows) : PCI, USB or IEEE1394
=> I though about using many low speed ADC (cheapier) to reach sampling frequency I 'd like to use, is it a good way to do this.
Which FPGA would be the most suitable for that project SpartanII, or APEX20k
TOTO2001 |
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talent85
Joined: 06 Mar 2006
Posts: 1
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| 06 Mar 2006 18:47 Re: Digital oscilloscope Project |
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hi everybody:
I am a final year student, now. i have a project is to develop a portable oscilloscope. But a problem is faced for the ADC input range. i have used the ADC TLC5540 to implement the A/D conversion. here, the problem arise that the ADC input range only from 0 to 2.6V.. it is not achieve my project requirement. who can help me to solve this problem. the requirements are:
Input range: -2.6 to 2.6V
Notes: I also confuse the circuit configuration of TLC5540.
The greatest appreciate for the people.
Added after 5 hours 39 minutes:
who know the TLC5540 circuit configuration. i confuse to construct it and test it.
the greatest appreciate for this.
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hugo
Joined: 01 Jan 1970
Posts: 243
Helped: 21
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| 21 Mar 2006 3:11 Re: Digital oscilloscope Project |
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Hi,
Does anyone have any idea what parts are inside the "Swordfish" Hand Held USB Oscilloscope (ADC,UC,RAM,FIFO...) ?
http://www.usb-instruments.com/oscillo_sword.html
Thanks
Last edited by hugo on 14 Apr 2006 22:19; edited 1 time in total |
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 01 Apr 2006 11:13 Re: Digital oscilloscope Project |
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Does anyone have any complete USB oscilloscope design for reference?
Is this project still active or in hibernation?
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x_eleman
Joined: 23 May 2005
Posts: 11
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| 05 Apr 2006 14:32 Digital oscilloscope Project and sources. |
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LCD Graphick display ,18f452 pic project , 1...1000 mhz and frekans meter help..!
Added after 7 minutes:
all codes
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 06 Apr 2006 7:08 Re: Digital oscilloscope Project and sources. |
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| x_eleman wrote: |
LCD Graphick display ,18f452 pic project , 1...1000 mhz and frekans meter help..!
Added after 7 minutes:
all codes |
Where?
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asif_warid
Joined: 18 Dec 2005
Posts: 15
Helped: 1
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| 11 Apr 2006 21:14 Digital oscilloscope Project |
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| go to fpga4u.com
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davorin
Joined: 07 Jun 2003
Posts: 1490
Helped: 8
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| 16 Apr 2006 17:03 Re: Digital oscilloscope Project |
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| asif_warid wrote: |
| go to fpga4u.com |
Please post correct domain name next time as fpga4u.com/net/org isn't registered at all!!!
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dainis
Joined: 15 May 2001
Posts: 1453
Helped: 56
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| 17 Apr 2006 10:01 Re: Digital oscilloscope Project |
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| davorin wrote: |
| asif_warid wrote: |
| go to fpga4u.com |
Please post correct domain name next time as fpga4u.com/net/org isn't registered at all!!! |
Maybe this ?
http://www.fpga4fun.com/
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 25 Apr 2006 6:16 Re: Digital oscilloscope Project |
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| It seems like the project has gone into cold storage!! No progress seen since months!
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oscil
Joined: 12 Jan 2005
Posts: 6
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| 26 Apr 2006 9:08 Re: Digital oscilloscope Project |
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http://www.mindbend.ro/eoscope/eoscope_en.htm
The Regard.
Who repeated this project?
Your opinions please
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 26 Apr 2006 17:04 Re: Digital oscilloscope Project |
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| oscil wrote: |
http://www.mindbend.ro/eoscope/eoscope_en.htm
The Regard.
Who repeated this project?
Your opinions please |
Nice project but without source code! 
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nikifena
Joined: 11 Dec 2003
Posts: 115
Helped: 8
Location: Bulgaria
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| 05 May 2006 15:20 Re: Digital oscilloscope Project |
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| CMOS wrote: |
| oscil wrote: |
h**p://www.mindbend.ro/eoscope/eoscope_en.htm
The Regard.
Who repeated this project?
Your opinions please |
Nice project but without source code! |
Are you sure ?
| Quote: |
| The archive contains the schematics, PCB and the byte-files needed to program the microcontroller and the cpld: eoscope_1.2.zip |
http://www.mindbend.ro/eoscope/download/eoscope_1.2.zip
good luck 
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 08 May 2006 14:26 Re: Digital oscilloscope Project |
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| nikifena wrote: |
Are you sure ?
| Quote: |
| The archive contains the schematics, PCB and the byte-files needed to program the microcontroller and the cpld: eoscope_1.2.zip |
h**p://www.mindbend.ro/eoscope/download/eoscope_1.2.zip
good luck |
Yes I am preety sure....The files are in compiled form. No source code is provided.
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nikifena
Joined: 11 Dec 2003
Posts: 115
Helped: 8
Location: Bulgaria
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| 09 May 2006 7:04 Re: Digital oscilloscope Project |
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uups sory. I think that this project have firmware (hex file..)
If you like the source code maybe you can ask the designer of this project
good luck
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klj55888
Joined: 20 May 2006
Posts: 13
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| 20 May 2006 8:40 Digital oscilloscope Project |
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| To me, this is too difficult
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 20 May 2006 10:51 Re: Digital oscilloscope Project |
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| klj55888 wrote: |
| To me, this is too difficult |
What is so difficult?
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nikifena
Joined: 11 Dec 2003
Posts: 115
Helped: 8
Location: Bulgaria
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| 06 Jun 2006 14:30 Re: Digital oscilloscope Project |
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Here is free version in russian of this project
http://www.usb-osc.narod.ru/
http://www.usb-osc.narod.ru/design.htm
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nikifena
Joined: 11 Dec 2003
Posts: 115
Helped: 8
Location: Bulgaria
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| 06 Jun 2006 22:35 Re: Digital oscilloscope Project |
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sch:
http://www.usb-osc.narod.ru/files/shem2.png
SCH in pcad2001:
http://www.usb-osc.narod.ru/files/sch.zip
PCB in pcad2001:
http://www.usb-osc.narod.ru/files/pcb.zip
Firmware:
http://www.usb-osc.narod.ru/files/OSC_USB_v2.2.BIN
Software:
http://www.usb-osc.narod.ru/files/USB_Oscillograph2.exe
some driver for usb scope:
http://www.usb-osc.narod.ru/files/Driver.zip
And other things:
http://www.usb-osc.narod.ru/download.htm
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fobyellow
Joined: 30 Sep 2004
Posts: 26
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| 14 Jun 2006 4:06 Re: Digital oscilloscope Project |
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any one have done a sample one?
i've made a acquisition board with 2*AD9215, and now writing code for UF32 USB-chip, next week the PCB might be OK
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angus
Joined: 11 Feb 2006
Posts: 3
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| 04 Aug 2006 0:11 Re: Digital oscilloscope Project |
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I really like all of the ideas presented here in this forum. I have been thinking recently about tackling a similar project and it's nice to know others think it is possible.
Instead of using a PC display interface, though, I have been thinking about having a built-in LCD display. I'm pretty new at all of this, so how would you do this? Thanks.
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 29 Aug 2006 2:55 Re: Digital oscilloscope Project |
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Why everybody use fpga ????
I'm also "trying" to design my personal DSO, but I found almost imposible to use a fpga because of 2 reasons:
1. Expensive (I've never used them so I don't have even the programmer) And also I'm from Argentina and I can't afford almost 500 u$s for a board...
2. I don't know how to use or program them :S......BUT it would be nice to learn about.
As far as I've researched, I can connect the adc directly to the usb ic and send samples all the time at a speed of 30Ms/s (16-bit) or 60 Ms/s (8-bit)....
And leave the trigger issue for the software....
That was my initial plan, but I wasn't convinced with the sampling rate.....
And now I don't know what to do, I'm kind of lost. I want to achive at least a 100 Ms/s rate!! (12-bit)...
I've seen lots of projects that uses memories to memorize all the samples and then send them but I really don't see the point of doing that because at 100 Ms/s you need a huge memory to store a 1Hz signal (for example). Ok, lets supose now that when the memory is full you transmit the stored data to the pc and when the memory is emty again you start receiving samples again. But what happends with all the samples you lost while you were sending data to the computer??...
Maybe I'm misunderstanding something.......Explain it to me if I'm wrong.
DOES ANYONE KNOW A BETTER WAY OF ACHIEVING SAMPLES RATES OF 100 Ms/s (or higher)??? ...(remember, without using a fpga because I can't afford them)..
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 29 Aug 2006 4:53 Re: Digital oscilloscope Project |
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| Gonzakpo wrote: |
| Why everybody use fpga ???? |
Because they are the fastest available devices in the market today.
| Gonzakpo wrote: |
1. Expensive (I've never used them so I don't have even the programmer) And also I'm from Argentina and I can't afford almost 500 u$s for a board... |
Check out http://www.digilentinc.com/Products/Detail.cfm?Prod=S3BOARD&Nav1=Products&Nav2=Programmable the sell FPGA boards at $99 !!
| Gonzakpo wrote: |
2. I don't know how to use or program them :S......BUT it would be nice to learn about. |
www.fpga4fun.com will be a good starting point.
| Gonzakpo wrote: |
I've seen lots of projects that uses memories to memorize all the samples and then send them but I really don't see the point of doing that because at 100 Ms/s you need a huge memory to store a 1Hz signal (for example). |
They use variable sampling rate. So you dont' require large memory for low frequency signals.
| Gonzakpo wrote: |
| But what happends with all the samples you lost while you were sending data to the computer??... |
Thats call blindness problem and it is present in almost all PC based DSO's unless they are using large FIFO buffers, capturing and sending data simultaneosuly.
I read somewhere, PC base scopes remain blind for 99% of the time because they are busy sending data to PC!!!
| Gonzakpo wrote: |
DOES ANYONE KNOW A BETTER WAY OF ACHIEVING SAMPLES RATES OF 100 Ms/s |
Not without FPGA/CPLDs and huge memory...preferably a FIFO.
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 29 Aug 2006 5:26 Re: Digital oscilloscope Project |
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thanks for the answer.....
I have a doubt about the variable sampling rate.....
How can I know the frecuency of the input signal ??....The only solution I can imagine is to change the sampling rate depending on the time base you've selected.
But I just doesn't make sense because I wouldn't be able to measure high frecuency signals using a large time base....(because of the low sampling rate)...
There must be another solution, like autodetection, but what would happen if the input signal isn't a "repetitive" signal.
The variable sampling rate doesn't convince me :S...maybe you know a better way to aply variable sampling rates???......
Regarding the FPGA's .....which model should I chose to start? (and keep using it for the rest of my life  ....I just don't like the idea of buying several boards JUST to see which is better) ......and...does the starter board comes with a manual???...I need something to learn from!
Last question, does anyone have a nice input circuit schematic for the a/d ?? (with "over tension" protections)
Thanks.
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 29 Aug 2006 5:41 Re: Digital oscilloscope Project |
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| Gonzakpo wrote: |
| The only solution I imagine is to change the sampling rate depending on the time base you've selected. |
Thats right!
| Gonzakpo wrote: |
But I just doesn't make sense because I wouldn't be able to measure high frecuency signals using a large time base....(because of the low sampling rate)... |
Actually variable sampling rate should be used along with variable low pass filter to avoid aliasing problems.
| Gonzakpo wrote: |
There must be another solution, like autodetection, but what would happen if the input signal isn't a "repetitive" signal. |
Well in that case intelligent hardware trigger design and good software calculations will be the only solution
| Gonzakpo wrote: |
The variable sampling rate doesn't convince me :S...maybe you know a better way to aply variable sampling rates???...... |
Go for large memory (GBs) then 
| Gonzakpo wrote: |
Regarding the FPGA's .....which model should I chose to start? (and keep using it for the rest of my life ....I just don't like the idea of buying several boards JUST to see which is better) ......and...does the starter board comes with a manual???...I need something to learn from! |
Spartan-3 from Xilinx are good FPGAs to start with and cheapest too!
| Gonzakpo wrote: |
Last question, does anyone have a nice input circuit schematic for the a/d ?? (with "over tension" protections) |
Check out download section of www.bitscope.com , they have old bit-scope schematic available.
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 29 Aug 2006 6:01 Re: Digital oscilloscope Project |
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WOW! that was fast! je
Thank you soooo much for your answer...
I'll consider learning the fpga stuff, It's a nice idea. But, when you desing something HOW CAN YOU SOLDER THAT ???? (I know that the word "solder"
doesn't exist, but I wasn't sure how to say that.......just to be sure that you've already noticed, I speak spanish )
Two more questions:
As I've said before, I can design the dso to sample all the time and send the samples to the pc at the same time. Without fpga and memories. (using a sample rate of only 30 Ms/s) ...but the question is: I've read somewhere that I CAN'T do that because the OS doen't work in real time, so I can't receive samples all the time....... Is that true? ...(I HOPE NOT :s)
How should I chose the correct trigger level?......
Well, I think that's all for now..... Thanks!
EDIT: I've been exploring the bit scope web and I found out that the sell 8bit oscilloscopes!!, that's a really poor resolution!....I was planing to use at least 12-bit, or maybe 14. ....
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 29 Aug 2006 8:20 Re: Digital oscilloscope Project |
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| Gonzakpo wrote: |
| I'll consider learning the fpga stuff, It's a nice idea. But, when you desing something HOW CAN YOU SOLDER THAT ???? (I know that the word "solder" doesn't exist, but I wasn't sure how to say that.......just to be sure that you've already noticed, I speak spanish ) |
You solder them using hot-air soldering station.
| Gonzakpo wrote: |
As I've said before, I can design the dso to sample all the time and send the samples to the pc at the same time. Without fpga and memories. (using a sample rate of only 30 Ms/s) ...but the question is: I've read somewhere that I CAN'T do that because the OS doen't work in real time, so I can't receive samples all the time....... Is that true? ...(I HOPE NOT :s) |
No windows is not a Real-Time Operating System. If you want to make a scope without memory, you should use Real Time ports of Linux like RTAI or RTLinux.
| Gonzakpo wrote: |
How should I chose the correct trigger level?...... |
That depends on your input signal level. If you want auto-trigger, the trigger level should be 0V or half the ADC resolution.
| Gonzakpo wrote: |
EDIT: I've been exploring the bit scope web and I found out that the sell 8bit oscilloscopes!!, that's a really poor resolution!....I was planing to use at least 12-bit, or maybe 14. .... |
Thats not poor....you'll hardly need resolution better than 8-bits.
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 29 Aug 2006 9:56 Re: Digital oscilloscope Project |
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why you say that 8.bit resolution is not poor???
For example, if I want to mesuare signals of 60vpp with only 8 bits i would be having a resolution of aprox. 0.2 V !! ....
I think that's a lot.
I'm disappointed with the matter about real time transmition :S :S
That way everything was soooooooo simple..... only an adc and a usb peripheral controller...
Is really imposible to do that??
Thanks!!
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 29 Aug 2006 11:52 Re: Digital oscilloscope Project |
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| Gonzakpo wrote: |
For example, if I want to mesuare signals of 60vpp with only 8 bits i would be having a resolution of aprox. 0.2 V !! ....
I think that's a lot. |
Would you ever require 0.2V accuracy at 60V? Think over it. If it of that much impostance you should go for 10 or 12-bit ADCs then.
| Gonzakpo wrote: |
I'm disappointed with the matter about real time transmition :S :S
That way everything was soooooooo simple..... only an adc and a usb peripheral controller...
Is really imposible to do that?? |
I didn't say impossible. It is possible on RTAI/RTLinux platforms but not on windows.
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