Re: Please advice for USB interaction

On 2006-04-14, Charles Sullivan <cwsulliv@xxxxxxxxxxxx> wrote:
On Wed, 12 Apr 2006 09:20:46 -0700, marco wrote:

Hello to all

I'm an engineering student trying to build a "data aquisition module"
using USB and Linux but I'm a bit lost.

Imagine this: I have an analog signal (for example this signal varies
between 0 and 3v) and I need to record in the PC the voltage of the
signal every 2 seconds (or every 2 ms). Then record this information,
for example, in a simple text file. I would like to use Linux and the
USB port for this. Is there any directions that you may give to me on
how to achive this task ?

Sincere regards
Marco

I hope you understand that a USB port accepts only digital signals and
you'll need additional hardware between it and the source of the analog
signal.

Supposing you have to build the hardware yourself, I wouldn't use the
USB port unless it's a neccessity because of the data rate that is to be
expected or you haven't got the possibility to connect it otherwise. I'd
look at some microcontroller based solution which could be connected to
the PC's serial or parallel port (depends on the data rate which is to be
expected, a serial port should be able to handle 115200 bits per second,
a parallel one should be able to handle up to a megabit per second if
neccessary). These interfaces are relatively easy to interface with, and
the microcontroller only needs to be programmed to read out a DAC and
feed that data to the PC. If you use the serial port, you might need
level shifters, though. If the data rate is low enough, you may even be
able to form the text file in the microcontroller and can just read the
data off a serial device file in the format you need. Using the parallel
port might mean you have to write a special little driver for the device
you're building, but that is usually not much trouble. If you can go
the serial or parallel route, I am happy to help, having built a few
similar things myself (an MP3 player which connects to the parallel port
and a radio clock that feeds data to the serial port). If you have to
use USB, I can't help you much, though.

Kind regards

Manuel
--
Homepage: http://www.hinterbergen.de/mala
OpenPGP: 0xA330353E (DSA) or 0xD87D188C (RSA)
.

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