8_ADC_16Dig_x20kHz_data acquisition module

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EvPa_264126
Level 7
Level 7
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Hello. I would like to hear your opinion on this version of data acquisition module:
ADS7818x8_DIG16_USBUART.zip  
I used the ADS7818 as an external ADC.
Short description:
Number of analog channels - 8.
Number of digital channels - 16 (there is the possibility of increasing to 32)
Frequency of data collection - 20 kHz
Transmission channel - USBUART.
It is possible to simulate the ADC data for debugging (in the absence of ADC chips)

   

To test the project there is a simple program - an oscilloscope (Win32 only).
Program features:
- View up to 8 ADC channels in real time on the screen of the oscilloscope.
- The ability to synchronize on any analog channel.
- View 16 channels of digital data on the other screen.

   

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ETRO_SSN583
Level 9
Level 9
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Is this a proposed design you are contemplating ? If so what

   

are the goals ?

   

 

   

Regards, Dana.

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EvPa_264126
Level 7
Level 7
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The aim of the project - a device remotely resembling a Low-Cost Multifunction DAQ NI USB-6000.
Such a device requires a very rare, so I do not need to buy it.
But there is a desire to create such a device on the PSoC ))

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ETRO_SSN583
Level 9
Level 9
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You obviously have sample rate limitations due to the overal number of channels that

   

need to be sampled.

   

 

   

Note sequencing SAR can do 8 bits, 8 channels, > 100 KSPS. 8 bits is most DSO

   

base rate.

   

 

   

Regards, Dana.

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EvPa_264126
Level 7
Level 7
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10-20 KSPS and 12bit - good enough for me.
I am concerned about 2 issues:
- there is no possibility to detect data loss or hanging device  during extended operation of the Registrar (many hours).
- alternative USB for more reliable data transmission in noisy environments.

   

 

   

 

   


 

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ETRO_SSN583
Level 9
Level 9
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You could always consider a 10/100 physical layer, that has

   

very robust protocol, used everywhere in industrial environments,

   

and a USB to eth dongle, cheap. Or USB to LVDS and back again.

   

Differential and quite robust in light of its very high speed capability.

   

 

   

I have used DAQ devices and I always felt GUI controlling them very

   

light, missing many capabilities. But then NI Labview easily solves

   

specific requirments for data logging, management.

   

 

   

Regards, Dana.

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HeLi_263931
Level 8
Level 8
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I'm not sure that Ethernet is much better than USB when used in noisy environments (providing that you use good cables). Ethernet can be quite lossy, and whereas TCP can handle that via retransmissions it can get slow then...

   

Something RS422, that works with higher voltage differential signalling, might be helpful.

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ETRO_SSN583
Level 9
Level 9
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This might be useful -

   

 

   

http://www.ni.com/white-paper/3509/en/

   

 

   

I had the opportunity to call on Andover Controls, building automation, and their

   

primary focus on Ethernet. USB was for simple local connections. The robustness

   

of TCP was relied on, even in elevator high current motor environments. Differential

   

signaling also used in some applications. But 90+% of machine and building control

   

done with ethernet.

   

 

   

I also called on several miltary suppliers, one specifically doing submarine work.

   

It was entirely ethernet based, again in very high noise environment due to pumps

   

of all sizes and makes, up to 150 KW. Thats some serious startup transients.

   

 

   

Regards, Dana.

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