Analogue input

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04 Feb 2012 01:21 #17373 by davidmp
Analogue input was created by davidmp
Hello all,

I have the need to monitor analogue signals coming from gas flow meters in CNCLinux and have searched on how to do this but in vain. Is there a HAL component that can do this? I was hoping to use the microphone input as an ADC and the headphone outputs as DAC because I only need two signals.
Has anyone done this? My parallel port is completely full and I have a mini-ITX system so not a lot of expansion space.

Thanks

davidmp

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04 Feb 2012 04:55 #17377 by cmorley
Replied by cmorley on topic Re:Analogue input
Interesting idea. Do you know of any projects on the web doing this hopefully ope source ones with code samples?

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04 Feb 2012 07:03 #17379 by andypugh
Replied by andypugh on topic Re:Analogue input
davidmp wrote:

I was hoping to use the microphone input as an ADC and the headphone outputs as DAC


I had a quick look at this a while ago, but couldn't figure out how to do it in a generic way.
There is a driver for the motherboard speaker (hal_speaker) but that is not what you need.
There might be some clues here:
wiki.osdev.org/Sound

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04 Feb 2012 07:11 #17380 by andypugh
Replied by andypugh on topic Re:Analogue input
davidmp wrote:

I have the need to monitor analogue signals coming from gas flow meters in CNCLinux and have searched on how to do this but in vain.


I think you can do this with a USB device and hal_input, if you don't need realtime.
One possible option for the USB hardware is a pokeys: www.poscope.com/pokeys56u

I can think of a way to do it with only the parport (and PWM to voltage conversion) but 2 channels of inputs + 2 outputs would be a minimum of 5 parport pins.

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04 Feb 2012 08:41 #17385 by cncbasher
Replied by cncbasher on topic Re:Analogue input
perhaps an arduino connected via usb

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04 Feb 2012 09:19 #17387 by andypugh
Replied by andypugh on topic Re:Analogue input
andypugh wrote:

There might be some clues here:
wiki.osdev.org/Sound


This looks more relevant:
tldp.org/LDP/lpg/node84.html
And seems to indicate that ioctl() is the way to get low-level access

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05 Feb 2012 00:27 #17409 by jmelson
Replied by jmelson on topic Re:Analogue input
andypugh wrote:

andypugh wrote:

There might be some clues here:
wiki.osdev.org/Sound


This looks more relevant:
tldp.org/LDP/lpg/node84.html
And seems to indicate that ioctl() is the way to get low-level access

I think sound cards are AC coupled, so won't work for slowly-changing inputs.
ioctl() only permits a privileged program to gain access to I/O registers.
The wav interface to the sound card moves blocks of raw samples in and
out, not a single sample a a time.

Jon

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05 Feb 2012 03:55 #17411 by skunkworks
Replied by skunkworks on topic Re:Analogue input
I am using an arduino to measure spindle temp and offset z automagically..

I followed these examples..

emergent.unpythonic.net/01198594294

works very well so far

electronicsam.com/images/KandT/testing/S...on%20HM2-Servo-1.png

sam

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05 Feb 2012 18:47 #17440 by cmorley
Replied by cmorley on topic Re:Analogue input
DIY oscilloscope using a sound card.
It seems 0 -.05 volts would be safe but others have used up to aprox 5 volts (but an AC current not DC)
They recommend a voltage divider to keep voltage to a reasonable number.
If you had an old sound card hanging around might be interesting project ....

www.micahcarrick.com/pc-sound-card-oscilloscope-linux.html
www.yann.com/en/diy-turn-your-gnulinux-c...cope-29/09/2010.html

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07 Feb 2012 01:47 #17477 by davidmp
Replied by davidmp on topic Re:Analogue input
Thank you every body for your replies. I didn't know the audio inputs were AC coupled. This will make it not work for my purposes so...
Does anybody have any ideas for a small DAQ that can be read through the RS232 or Ethernet ports and display values on AXIS?

Thanks

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