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From: Nor Muzakkir on 11 Apr 2010 11:05
Hi Jan,

Thank you very much again for all your kind replies. I tested and yeah i did get a "delay" signal which is not the signal that i want when i wanted it. i did notice before this the MatLAB real-time doesnt have any NI USB-XXXX in the NI lists, thanks to you now i know why :)

I was and still searching on how to overcome this problem. in your opinion what should i do?

from my understanding, if money is not a problem to me, i should switch and use proper DAQ as u mentioned such as (PCI,PCIe, etc.) and use real-time softwares.

however that is not an option to me. i'm planning to construct an ADC(using PIC) and interface the signals to the PC using serial port. currently i'm thinking of buying a PCI or PCIe Serial Port(with built-in IC of 16C550 or 16C950) that have fast serial transfer rate(1.5Mbps and up to 15Mbps) as these hardware are cheaper than buying new DAQ from NI.

will this setup help in overcoming my problem? or at least will it be significantly faster than using my current USB DAQ?


Thank you.
From: Jan Houska on 12 Apr 2010 04:30
Hi Nor,

with RS232, you will at least get exclusive connection, but then you
will have to convert the data to serial format and back. You also cannot
expect immediate response of the computer side, the RS232 port in the
computer can have significant latencies. With the solution you propose,
you risk spending some additional money and lot of effort on something
that is just marginally better than your original setup.

If you need deterministic real-time performance, PCI or PCIe is the only
reasonable way to go. I would really recommend to buy a proper data
acquisition board. It will pay off very soon, and, after all, it's not
at all expensive compared to time spent by trying to put some custom
design together.

Good Luck, Jan


Nor Muzakkir wrote:
> Hi Jan,
>
> Thank you very much again for all your kind replies. I tested and yeah i
> did get a "delay" signal which is not the signal that i want when i
> wanted it. i did notice before this the MatLAB real-time doesnt have any
> NI USB-XXXX in the NI lists, thanks to you now i know why :)
>
> I was and still searching on how to overcome this problem. in your
> opinion what should i do?
>
> from my understanding, if money is not a problem to me, i should switch
> and use proper DAQ as u mentioned such as (PCI,PCIe, etc.) and use
> real-time softwares.
>
> however that is not an option to me. i'm planning to construct an
> ADC(using PIC) and interface the signals to the PC using serial port.
> currently i'm thinking of buying a PCI or PCIe Serial Port(with built-in
> IC of 16C550 or 16C950) that have fast serial transfer rate(1.5Mbps and
> up to 15Mbps) as these hardware are cheaper than buying new DAQ from NI.
>
> will this setup help in overcoming my problem? or at least will it be
> significantly faster than using my current USB DAQ?
>
>
> Thank you.


--

--
Jan Houska HUMUSOFT s.r.o.
houska(a)humusoft.com Pobrezni 20
http://www.humusoft.com 186 00 Praha 8
tel: ++ 420 284 011 730 Czech Republic
fax: ++ 420 284 011 740
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