Re : NI-845x : I need some information about clock .

[Julie26000]

Hi,

My problem is that there is , on the CLK signal(on module NI-845X), 8 impulsions after there is a low signal during 10 µs and after 8 impulsions ect..

I would like to have a regular signal composed by just impulsion and not low signal.

Sorry for my english.

And thanks if you have some information for me.

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Bonjour,

Mon problème est le suivant:

j'ai un signal CLK (avec le module NI-845X), composé de 8 impulsions puis un signal bas pendant 10µs puis mes 8 impulsions reprennent et ainsi dessuite

J'aimerai avoir un signal CLK régulier composé seulement d'impulsion , comme un signal clock normal en faite.

J'espère que quelqu'un pourra m'aider

Bonne journée

[Remi.D]

Hi Julie26000,

I think that you are speaking about the SCLK 854X. In dead, this is an expect behavior for the SPI protocol.

This SPI Timing Characteristic can be found since the link below (P 7-2):

NI-845x Software User Manual:

http://www.ni.com/pdf/manuals/371746b.pdf

Because this behavior is part of the SPI API, you can not change it. What is the operation you want to achieve? Why do you need a perfect clock? What is the purpose of your application?

Best regards,

[Julie26000]

Hi,

Thanks for your reply,

that i would like to do is to create a graphical user interface for a MicroWave, and i must send some informations in continue and not 8 bits by 8bits. My memorie not understand and not reply with this clock.

I'll try to use DIO fonction in order to simulate a best clock. But I have some difficulties to understand how use it.

If you have some information about it?

Thanks for all,

Kinds Regards

[Julie26000]

Hum sorry Microwire and not microwave , but i think that you have understood

[Remi.D]

Hi Julie26000,

What is the frequency of your clock, and what is the precision you are expecting? 

Best regards,

[Remi.D]

I julie26000,

Another thing that you sould keep in mind regarding digital I/O is that all updates of DO lines are software timed. This means that the accuracy of your clock is necessarily influenced by your OS (Windows...). 

USER GUIDE AND SPECIFICATIONS - USB 8451 (P.6)

http://www.ni.com/pdf/manuals/371709b.pdf

To perform digital output you can find some examples from LabVIEW. I invite you to read this KB above, whch deals with this topic.

Writing and Reading to the DIO Port on USB-8451

http://digital.ni.com/public.nsf/allkb/789F3D731F481752862572C700635B52?OpenDocument

This example above, allow you to create a clock by inverting the booléan value at each while loop iteration. The "wait until next multiple ms.vi", it's your timing between two booléan generation, so it's like your frequency.

Best regards,

[Julie26000]

Hi,

thanks.

And for your question, that i want to do is to simulate a SPI signal for the microwire. All my signals (CLK, CS, MISO,MOSI) must be start in the same time, for this i think i'll use a "boucle cadencée"(sorry i don't know the name in english). I'll recreate the clock , CS, and MOSI . and for the clock i need a frequency about 1000 kHz.

But i'll use your programme for this time .

Thanks for all.

kinds regards