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NI USB 845x SPI Problem


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Hello everyone,


I have a small problem with SPI communication. I'm using NI USB 8452 module and LabView 2013 with driver NI USB 845x 14.0. As a first step I ran the example from attached library called "Atmel AT25080A Write.vi". The problem manifests as logic "0" all the time on MOSI and MISO lines. No Data transferred. CS and CLK works properly. I never use pull ups when using SPI but maybe I should? The question is did anybody meet the same problem while using this usb 8452 module? All 4 SPI lines connected directly to oscilloscope. Waiting for any reply. Thanks in advance.





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Thanks for answers!


I have never used a NI USB 8452 but......


According to the manual it has on board pull up resistors that need to be enabled for Vref ≤ 1.8 V. Whats your Vref?


Yes, there is info about that, but in my opinion refers mostly to I2C communication where you have to externally pull up the SDA and SCL lines. The Vref is an output pin which you can use to pull something up (not used in my application). Used mostly when you want to shift level logic between 845x and device connected. When using SPI, you are selecting I/O Voltage Level which is in my opinion the same thing, but you are doing it inside 845x. There is no info in datasheet regarding pulling up SPI lines. I see it this way.



Don't you hook it up to a device?


Don't understand. You mean it will not work without any device connected? I think I should see the signal on MOSI Output even if nothing is connected.



Anyway! I found the solution. The NI 8452 module I use last time is damaged! I have in my company few of them, I took the next one and problem disappears.



Properly installed device with proper driver for your LabView version (very important) should be enough to run SPI example and see how it's working.


Edited by Dawid
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