Re: gEDA-user: Any DIY USB Scope project on schedule? Or some recommmendation?

[Ales Hvezda <ahvezda@xxxxxxxxxxxxxx>]

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-- Cut here --
Delivery-Date: Tue, 23 Nov 2004 22:46:42 -0500
From: Darrell Harmon <dlharmon@xxxxxxxxxxxx>

Christian Frisson wrote:

>Hi,
>
>I'm a audio-engineering student in need of a cheap portable 2-way scope that
>could travel with me easily. Instead of second-hand standard oscilloscopes and
>handheld advanced multimeters, the idea of a high-transfer-rate (neither serial
>nor parallel) peripheral that could be attached to a computer in order to use
>its screen and perfs seduced me. The latest DS1M12 "Stingray" from
>USB-Instruments (http://www.usb-instruments.com/), rated at 300? circa, looks
>like a killer for what I need, and it ads tonegen and partial Linux-compliance.
>I'm not into HAM radio (at least FM synthesis), so the sampling specs seem to be
>suitable. When it comes to tube homebrewing, I think an X10 probe should enlarge
>the 0-50V span to 0-500V without damage.
>
>Before diving in, have I missed something particuliar that should make me turn
>away?
>
>Do you know if such a device has been turned into a DIY project? With COMEDI
>(http://www.comedi.org) and/or xoscope (http://xoscope.sf.net) compliance?
>
>Cheers,
>Christian Frisson
>
>
>  
>
Any reason not to consider a used scope?  I paid less than $100 for mine and it is a 200MHz.  (HP1715A)

One problem I see with the USB thing is that troubleshooting parasitic oscillations in an amp could be difficult as they tend to go high in frequency (I have seen 100MHz).

The next project I have planned after doing a revision on my SBC is a digital scope add on board for the SBC.  I will be using 80MHz ADCs (ADS5410 from TI), and plan on undersampling.  The ADCs have 1GHz analog bandwidth.  Should be a fun project.  I am also adding an arbitrary function generator using a 160MHz DAC.  As you can see I am going toward the high end and it won't be cheap (Lots of $10 -$30 parts that add up fast).

Maybe someone else should design a low cost open hardware scope with about 20MHz bandwidth.  ADS831s are cheap, 8bit 80MHz ADCs.  Maybe one of the AD Blackfin DSPs for control.  The input buffer can be made quite simply using JFETs.  Possibly a PGA for all the gain before the ADC.

-- 
Darrell Harmon
100x100mm SBC running GNU/Linux:
http://dlharmon.com/sbc.html