Oscilloscope

[YahooArchive]

Hi,
I'm just getting started with the ArmMite. Has anyone made up an oscilloscope
using the ArmMite? Looking for software that will enable the ArmMite to be used
as an oscilloscope. It has A/D converters right there, communications to the PC,
digital inputs for triggering, etc. Seems like a natural to me. Thanks.

[YahooArchive]

>Has anyone made up an oscilloscope using the ArmMite? Looking for software that
will enable the ArmMite to be used as an oscilloscope. It has A/D converters
right there, communications to the PC, digital inputs for triggering, etc. Seems
like a natural to me. Thanks.
>

There is a logicscope demo which capture 16 digital inputs at up to about 1
Msample/sec.

The A/D could capture upto about 100 Ksamples/second. OK for some slow signals.

The SuperPRO has a DMA and combined with the timers could capture faster digital
(probably upto 10 Msamples and maybe 250 K analog samples)

[YahooArchive]

I've looked all over for the Logicscope demo and can't find it. Where do I look?
Thanks.

[YahooArchive]

> I've looked all over for the Logicscope demo and can't find it. Where do I
look? Thanks.

check the help files installed for BASIC or on Coridium Support web page

in the Hardware Library, it has its own section

or search the helpfiles for logicscope

[YahooArchive]

Hi. Found it, but it appears to only do logic levels, as opposed to A/D
readings. I'm looking for an application where the Armmite board is used to
measure and display analog voltages, preferably at least two channels. Will the
Logicscope do that? Thanks.

[YahooArchive]

> Hi. Found it, but it appears to only do logic levels, as opposed to A/D
readings. I'm looking for an application where the Armmite board is used to
measure and display analog voltages, preferably at least two channels. Will the
Logicscope do that? Thanks.

The PC side, was adapted from a Tcl sample application

http://wiki.tcl.tk/7137

The ARM side code is published as part of the BASICtools code.

You could use a similar mechanism to change the LogicScope to 2 analog traces.
The best you could do would be about 50 Ksamples/sec. Good for low frequency
work.

[YahooArchive]

IMHO the only way to do this is to add some additional hardware, at least to
capture data probably some op amps to level shift the signal, a parallel
converter and a FIFO with a CPLD to trigger.

Its a pretty simple circuit and could easily do upto 50 MSamples/sec.

It would even double duty as an 8 bit logic analyzer.

There is a kit at SparkFun that uses an AVR, which runs at 5 MS/sec. With the
DMA of the SuperPRO you might be able to 50 Msamples but it would not have any
trigger, just reading the port in BASIC maybe 8 Msamples, in C probably 15-25.

[YahooArchive]

That is a pretty nice little project. 50 MSamples/sec is usable. Would you build
a hardware trigger, or do the trigger in firmware instead? Or both?

-Ron

[YahooArchive]

> That is a pretty nice little project. 50 MSamples/sec is usable. Would you
build a hardware trigger, or do the trigger in firmware instead? Or both?

I did some looking around Digikey for parts.

While a number of years ago FIFOs were being used widely, that's not the case
anymore, so even small ones are pretty pricey.

The ADS830 is a good choice for the converter and its app notes shows how to do
the level shift (add control via PWM or similar).

Next would be where to stuff the data. Maybe DMA into the CPU could keep up
(big if), but you'd still need an external trigger. While a CPLD could do this
and even generate controls for a standard SRAM, maybe the best way to go would
be to just put a small FPGA out there. A Xilinx Spartan could easily capture
all the data internally and provide all kinds of triggering. And the Spartan
could also capture data for a high speed logic analyzer.

Since this was posted, I never did get around to building a logic analyzer based on an FPGA. The main reason is that others have already done it and you can pick up one for a couple hundred dollars. When I last looked (about a year ago) the best price performance was the Link Instruments MSO-28, and I've bought 3 of them so far for Coridium. That and my netbook much better than any scope meter and more portable than a traditional scope.

[YahooArchive]

Hi, all.
I am familiar with the PC based scopes, but they all are DC coupled, only.
There are some projects to use a voltage to frequency generator to force the PC
sound card to run with DC coupling but that has drawbacks. I was hoping that
there was some published program out there that would allow the Armmite to be
the input module for a PC based oscilloscope, in that it has A/D converters on
it that are dc coupled. I have some automobile work I need to do and want a
scope to look at the signals. Planned on using a laptop with the Arrmmite hooked
on it. It sounds like there are no published programs to use the Armmite with
the PC as a scope. Thanks, though. Irv

To: ARMexpress@yahoogroups.com
From: pompey2@yahoo.com
Date: Tue, 4 May 2010 22:27:02 +0000
Subject: [ARMexpress] Analog Scope