Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Highlighted
Valued Contributor III
1,721 Views

Cyclone IV - Using high impedance in GPIO

I have a project with 14 bidir. I use to test integrated circuits from college.  

 

i use the 36 gpio pins in a protoboard with a flat cable. but when i put the bidir in high impedance, all outputs go to high level (but they continue in high impedance).  

 

Firstly i think the weak pull-up resistor is on (and turn off). After I tried turn off all programmable adjustments. Nothing worked. 

 

I am a computer scientist and maybe my fail is in eletronic level. I don't know. 

 

Any suggestions? What can you do to help me?
0 Kudos
6 Replies
Highlighted
Valued Contributor III
17 Views

What is driving the wire when you put the FPGA pins in high impedance?

0 Kudos
Valued Contributor III
17 Views

 

--- Quote Start ---  

What is driving the wire when you put the FPGA pins in high impedance? 

--- Quote End ---  

 

 

The GPIO is connected to protoboard (flat cable). I didn't understand your question, but nothing is connected between pins and protoboard when are in high impedance. 

 

https://www.alteraforum.com/forum/attachment.php?attachmentid=6918  

 

FPGA >> PIN <> GPIO <> Protoboard
0 Kudos
Highlighted
Valued Contributor III
17 Views

Since there isn't anything else driving the wire, when the bidir signals go into high-impedance state, the status present in the wire is "random".

0 Kudos
Highlighted
Valued Contributor III
17 Views

 

--- Quote Start ---  

Since there isn't anything else driving the wire, when the bidir signals go into high-impedance state, the status present in the wire is "random". 

--- Quote End ---  

 

 

So, why can I do?
0 Kudos
Highlighted
Valued Contributor III
17 Views

 

--- Quote Start ---  

So, why can I do? 

--- Quote End ---  

 

 

What's the problem? 

 

If you need them low add very high value pull down resistors from each line to gnd. 

 

 

Nial
0 Kudos
Highlighted
Valued Contributor III
17 Views

debugmaster, 

the question is: what behavior do you need?
0 Kudos