microcontroller synchronize

[siva0182]

I have mangead to acquire data from a yokogawa source meter thro labview using the drivers. .I have an external microcontroller doing multiplexing /switching..and a separate sourcemeter to source and measure. The aim is to synchronise every "measure" action by the source meter with every swithcing done by the microcontroller. Thoudh the delay timings are roughly the same..the electrical starting transient times are different for both the circuits so any suggestions to synchronize these two circuits are welcome?

[LuI]

Your µC must have a controlling interface, usually via RS-232 or USB. Use a sequence of {switch | measure}, probably inside a loop to synchronice your tasks. Depending on the expected settling time you may want to add some wait nodes inbetween switch and measure.

If this SW-based sync is'nt quick enough your µC must poll a digital signal you send from LV or even better your meter may provide as a 'data ready' signal.

Can't be more specific without more details.

  Greetings from Germany!
--
Uwe

[siva0182]

yes I have a Rs232 interface for the micro controller..I will try to switch from matlab as you say.. But Will using 2 COM ports simultaneously create any problem? any precautions to take while handling two ports simultaneously?

[siva0182]

sorry i meant to say that i would try from labview (not matlab..)

[LuI]

As always - it depends...

AFAIK the standard operation mode for RS-232 using VISA is asynchron, so you can operate as much serial ports in parallel a you want and your system can handle. This can, however be changed which than could lead to problems.

But in your case you need to operate both ports alternating in order to get the desired sync. Pseudocode could be

Open & configure Port 1

Open & configure Port 2

While not done

  set your switch

  wait for settling

  get your data

  store data in a chart or in a shift register

 while_end

 Close ports

save your data

If your data size can not be stored in RAM (more than, say, several 100 MB) you need to use a producer-consumer architecture that can save data in a file while other (newer) data is acquired. But this is overshoot in case of your data size is (much) less than the above mentioned number.

Greetings from Germany!
--
Uwe

[siva0182]

Thanks a lot .I will try it next week and come back with results I get.

regards

Siva 

[siva0182]

As suggested I tried to do a switching and and then a reading in awhile loop.But to do the sequeential processing of switch  wait and read processes .I guess I need to use sequence frames.

But my doubt is both switching (which wil have visa write function ) and read( which will have instrument driver Vi's) will require resource name wires and error wire as inputs and will send as outputs.wait process will have no inputs and outputs.

So How do I incorporate these process in a sequence structure ..coz I think the frames should have common outputs????

regards

[LuI]

You may use a sequence or put the wait node into a subVI that routes the error chain through. I would have send you my 'Wait with error chain.vi', but I'm not at office right now.

[siva0182]

My concern is If I use a sequence how do I wire in the resource wire name and error wires into different frames for different resources?

alternatively If I can use a wait node..can you please send me your file when you are back in office tomorrow.

[lamlin]

Hi Siva,

I am doing a project which is to measure thousands of transistor's current through labview. Unfortunately, I met with many difficulities in this project. One of the major problem is to measure the transistor and switch to the next one synchronize. I searched on NI website and I found you met with the similar problems a few years ago. Would you help me?

I use multiplexer to switch the transistors measured by source meter.  The aim is to synchronise every "measure" action by the source meter with every swithcing done by the microcontroller, just like what you mentioned before. I use keithley 2636 as the source meter and keithley 2400 to offer a signal to control the microcontroller. However, this two instruments can not start at the same time though I put them in the same "for loop" in the labview program. Would you tell me how can you solve this problem? Thank you so much!

LIN