Cobra IO21 PullUp Resistor

NETMF & Gadgeteer
1

I have a Cobra right out of the box. Nothing connected except USB and external power. I can’t get IO21 signal to pullup. No issue with other IO’s.

Are all IO’s tested before shipping? Is IO21 reserved for something not documented?

Thanks -AP

2

It looks like IO21 is used for EMX / Cobra board detection it has a 10k pulldown so the software knows whether its a lone EMX module or if its mounted to the Cobra…

I should imagine it is documented somewhere…

Cheers Ian

3

Please check schematics http://www.tinyclr.com/downloads/Cobra/FEZ%20Cobra_sch.pdf

This is not documented beside schematics but we use this in our libs to detect Cobra vs EMX DevSys if necessary…as a future need

4

Hi everyone

Does it mean that we should not reuse IO21 for an other purpose? Should we keep it as a GHI reserved pin?

I’ve just received my two EMX modules and start to write my schematic for a custom PCB. This post is therefore very relevant to me.

5

You can use it

6

Hi all,

Let me pull this topic on top of the list for a quick question : So as IO21 is pulled down to 10k on the Cobra, does it mean that it is reserved and unsable if the EMX is mounted on the Cobra ?

Thanks.

Stephan.

7

I believe this means you can use it if you want to, but it WILL be pulled down and you can’t change that.

8

FYI, PDF moved to http://www.ghielectronics.com/downloads/FEZ/Cobra/FEZ%20Cobra_sch.pdf