trouble specifying TTL for digital outputs from PCI-6221

[emilyd]

Hi!

I'm trying to generate TTL output signals using a PCI-6221 daq board - within Labview, I'm using DaqMx to create two digital waveforms and then write these. When I plug in an oscilloscope, the shapes/frequencies of the signals are correct, but the lower value is 0V, and the higher value is 1V, rather than the TTL values. Is there a way to specify these voltage levels to TTL within the software? I see from NI help that "do.logicfamily" exists to specify TLL, but when I add a property node and connect it to the channels, I do not see Logic Family as an option under "digital output." Let me know if you have any ideas!

Thank you,

Emily

[crossrulz]

Set your oscilloscope to use 1MOhm impedence.  Your problem is that the maximum current for those DIO is 24mA.  1V/50 Ohms = 20mA.  So you are current limiting the digital outputs.  If you need more current, then you need to add in some digital buffer chips that can output more current.