TiynFPGA all non-programmed pins ouput low voltage [Solved]


#1

Hello!

I am new to FPGAs and i’m still trying to figure out things, i am sorry if this is an oversight on my part.

My TinyFPGA BX when running a verilog led test program (simply outputs power through PIN_1) also gives a small amount of power on all the other pins which is enough for the led to partially glow. I can’t find much on here except mention of pullup behavior, which i tried disabling in the .pcf file to no effect on the outputs. What i tried (with each pin name and no in place of yes): set_io -pullup yes [port] [pin]

Is there something i’m doing wrong? I saw on the one forum post that the chip sets all pins to pullup by default until it’s done booting? But why after it’s done booting are the pins still partially on?

Also is there any documentation for the pcf file?


#2

Hi,
This is expected and normal. Generally un-set pins will default to being “Hi-Z” (high impedance) inputs. However, they will still leak enough to power small LEDs dimly (the pull-up option you mention might change the “dimness”).

If you want you can set them to high, low or input explicitly (but typically no reason to).

-Xark


#3

Hi,

I have seen similar behavior. While I am not doing rocket science at this moment it would be interested in discussing solutions to this problem. In a production setting would I also need to modify the bootloader?