6509

[Himanshu_77]

Hi ,

 I am facing an issue regarding the DIO read write.In Max first I am setting the port 0 with all lines set to high.Now when I read back the same port for some few seconds I read the input as high which I set it ,but suddenly some of the lines (randomly)are becoming low. I am using USB NI DIO 6509.

Any idea what's the issue???

[SnowMule]

What's it got connected to it? Anything?

There's a weak internal pull-up resistor on the DIO board, it doesn't take much to pull the DI lines low.

Are you configuring the port as "all output", "all low", "start", "stop", then reconfiguring the port to "all input", "start"?

[crossrulz]

You will likely just want to find a digital buffer to increase the available current.  This is fairly common with DIO trying to drive relays.

[Himanshu_77]

Yes I am doing the same just first making port as output and setting all the lines as High and then making the port as input and reading back the values I had set earlier.What I am observing is that the Lines are getting low after few seconds of read.

[crossrulz]

---

@Himanshu_77 wrote:

Yes I am doing the same just first making port as output and setting all the lines as High and then making the port as input and reading back the values I had set earlier.What I am observing is that the Lines are getting low after few seconds of read.

---

Don't change them to inputs.  They have a built-in pull down.  If you are not driving them (by changing to inputs), then the voltage will bleed through these pull-down resistors.  You can still read a digital output.

What we always did was have another port that could read the DIO after all of the buffers and what no to make sure the UUT or whatever saw the outputs.  Just a thought.

[Himanshu_77]

Hi,

Generally when I set the values in the Port it should be set till I change it,but in 6509 what I am observing is that after I set the values on the port and trying to measure externally using the Oscilloscope its going low after few seconds(1-2 sec). So to check that behavior I performed the test by first writing the port and then reading the port and I am seeing the same behaviors is this card does not latch the output once I set it.

[crossrulz]

Can you post your test code? Also, what all is hooked up to the DIO?  When is the measurement being taken?  How much current should be being used by the attached circuit?

[clint100]

I had the same problem.  One of my channels (P8.5) on the 6509 wasn't reading (hi or lo) and when I ohmed it out from the UUT to the PXI chaissi there was continuity.  So I started to inject a 3 vdc level into each channel on the port (8.1,8.2, etc.) , monitoring it in MAX  ( Test Panel).  Each "good" channel toggled high when I injected 3 vdc and low when I tuned the supply off.  If I remove the connection to a channel the led came on.  I expect that from your description if there are pull ups.  When I removed the cable from the back of my PXI chasiss and went thru ports one by one,  after a few seconds some channels would go low and nothing was connected.  I was doing this to see if maybe I had a short in my test station.

Can you summarize??

In MAX w/o the cable connected to the 6509 what should each led be ( on/off)?

If I can toggle what I think is the bad channel and read a hi and lo( external dmm)  when I expect BUT can't read an injected signal, do you think that channel is bad??  Is it possible to output a value but not read one and still be a bad channel?

[DNLe]

Hi,

Can we use dio 6059 to generate a spi signal?

Thanks,

DNLe

[clint100]

I'm not not an expert on SPI but had to do a crash course on it when our customer expected me to use it.  SPI is a protocol...I think thats the right term.  Its all about timing.  The device you are talking to has, if I remember right ( I'm done w that project) , at least 3 lines.  A sck,sdo and cnv.  There is also 2 lines that tell whether or not the data is read on a rising clk edge or falling.  National has tons and tons of information regarding spi.  I will tell you this...at least for me, use a device meant for spi interface unless you have a LOT of time.    The customer purchased a National FPGA card when I could have used National's usb 8451.  There are more examples and it was meant for spi protocol. 

After all that I'm not sure you can use the 6509 for spi.  Probably but not w/o a lot of effort