digital io

[clint100]

Can you "measure" a 1 KHZ,3VDC squarewave on a digital port of a PXI6723??  I trying to make sure the connection is good so I'm sending the (sq) waveform from the analog out thru a differential driver/receiver circuit and back  into the DIO.  I'm testing that the signal toggles at my freq.  hi>lo>hi>lo>hi>lo...etc..

This maybe a diff post but..

The output of my differential driver is high impedance when its off and from what I understand when the 6723 sees a high impedance there is a pull up to ~3 volts so it would read a high if I looked at the port/channel.  So my question is how could I tell when the signal to the diff circuit is low??

[crossrulz]

---

@clint100 wrote:

Can you "measure" a 1 KHZ,3VDC squarewave on a digital port of a PXI6723??  I trying to make sure the connection is good so I'm sending the (sq) waveform from the analog out thru a differential driver/receiver circuit and back  into the DIO.  I'm testing that the signal toggles at my freq.  hi>lo>hi>lo>hi>lo...etc..

---

You can't capture a waveform with the DIO.  However, you could measure the freqeuncy with a counter on the same card.

---

clint100 wrote:

The output of my differential driver is high impedance when its off and from what I understand when the 6723 sees a high impedance there is a pull up to ~3 volts so it would read a high if I looked at the port/channel.  So my question is how could I tell when the signal to the diff circuit is low??

---

Put in a pull down resistor.  10k should do it easily.

[MarcoMauri]

---

@crossrulz wrote:

You can't capture a waveform with the DIO.  However, you could measure the freqeuncy with a counter on the same card.

Hi crossrulz,

capturing a digital waveform should be possible (as shown in example shipped with Labview Cont Read Dig Chan-Int Clk.vi).

Am I wrong?

Regards,

Marco

[crossrulz · Accepted solution]

---

@MarcoMauri wrote:

---

@crossrulz wrote:

You can't capture a waveform with the DIO.  However, you could measure the freqeuncy with a counter on the same card.

Hi crossrulz,

capturing a digital waveform should be possible (as shown in example shipped with Labview Cont Read Dig Chan-Int Clk.vi).

Am I wrong?

Regards,

Marco

---

If you read the spec of the PXI-6723, the DIO are only software timed.  Therefore, the values are only read when the software tells the card to grab the current value.  The timing will not be deterministic (which I think is kind of important).  If you have hardware timed DIO, then a digital waveform could be captured.

[clint100]

You're exactly right.  I tried it anyway and it read the line "when it wanted to". For example, I put in the squarewave and tried to read the line.  After running my vi to read the digital line x amount of times sometime it would be high sometime it would be low, and not in any pattern.

Thanks