PCI 6516- setting P0.0 to high causes voltage drop on external power supply

[Jaime F]

Hi

From your post I can infer that you are trying to do a digital output so for example if you are using Port 6 as an output port, you must connect P6.VCC to the positive lead of an external power supply (5-30V DC) and P6.GND to the negative lead of the power supply. The output will then switch between 0V and the supplied voltage.

After looking at the manual I can see you have the correct connections. Yes, there is the possibility that the pin is damage, so let's go through some troubleshooting. Some questions I have for you are: what happens if you change the positive lead from pin 5 to 14, 28 or 27, do you get the same behavior?, How are you measuring the voltage, DMM, SCOPE? What do you read in other lines from port 0 when they are set to high? Can switch the lines from any other port to the correct Vcc but port 0?

Also&nbsp;I would like you to read this knowledge base and check if this is the behavior you are seeing, <a href="http://digital.ni.com/public.nsf/allkb/8D46388A20C5A23E862572B8007E8C82" target="_blank"> Expected Voltage Drop on the Digital Output Lines of NI-651x Devices</a> .

Waiting for your reply

[amamin]

Sorry for the late reply. Here are the answers for troubleshooting: - what happens
if you change the positive lead from pin 5 to 14, 28 or 27, do you get
the same behavior?yes-How are you measuring the voltage, DMM, SCOPE? DMM-What
do you read in other lines from port 0 when they are set to high? They all function as expected except for line 0. However, if line 0 is set to high, and all lines in port 0 are high, then all lines give a small voltage (about 0.4V) and pin 5 is around 1.85VC an switch the lines from any other port to the correct Vcc but port 0?-yes, as long as port0 pin 0 is low. the change happens to the power supply, so all other ports are affectedthanks alot and appreciate your help