Gimzo 2 custom On/Off button?

Hi Mark,

The information is in this thread: http://www.element14.com/community/community/designcenter/single-board-computers/gizmo2/blog/2015/07/30/gizmo2--flash-bios-to-autostart-on-power-up .

In summary you can either solder your custom switch directly across the switch on the circuit board (not ideal) or access the same connections on a PCIe connector or use the debug connector which

is probably easiest (this is all in the schematic PDF doc).

You can see in the PDF in the page 3 block diagram that the power button circuit is on page 21 in the PDF, and that the relevant signal is called PWR_BTN and that it is connects to ground via a 10 ohm resistor.

So you'll need an external switch and a 10 ohm resistor in series.

By doing Ctrl-F and searching for the text 'PWR_BTN' in the PDF, you'll see that the signal is brought out to the debug connector marked J13, pin 10.

You can use pin 15 as the ground end of the switch. Pin 1 of the debug connector will be indicated with a square shaped pad, and the pin numbering is in a zig-zag fashion as shown in the

schematic (I don't have a Gizmo2 near me to confirm with a multimeter, but you could easily confirm by putting one end on pin 10, and the other at the power button on the board, and you should measure

10 ohms resistance.

I'm more a programmer and the schematics are a bit confusing. I understood the part about connecting a button and 10 Ohm resistor in series, but not which pin to which pin (yes I prefer the pins over soldering on the PCIe or across the stock button).

Sorry. I didn't expect to do have to do any hardware mods for something this trivial, but luckily it seems the only hardware modification I'll be doing.

Check out this post where I added an external power and reset button: http://www.element14.com/community/community/designcenter/single-board-computers/gizmo2/blog/2015/01/28/gizmo2-adding-external-pwr-and-rst-buttons

Oh wow, so much great tutorials I'm having hard time finding

So you didn't use a resistor?

Is there any requirement for what button can be used. All I know is buttons have a maximum current rating, this shows how little my electronics knowledge is. But it's going to be fun programming the Gizmo after I get this figured out.

PS. Is that a 3d printed enclosure? That's another hobby of mine.

Yes,

mine is here: http://www.element14.com/community/community/designcenter/single-board-computers/gizmo2/blog/2015/01/26/gizmo2-3d-printable-enclosure

and Brian made an even better one: http://www.element14.com/community/community/designcenter/single-board-computers/gizmo2/blog/2015/01/31/gizmo-2-another-3d-printed-enclosure

Just a preview I am working on and will be open and posted soon (maybe in a week or two):

Gizmo2 + internal SSD + External HDD with secondary SATA and 5V SATA Power, external power, power-on and reset buttons and something more. Honestly, this project has not only been inspired by the post of fvan but his post confirmed me some of my doubts and made this possible. Coming soon

Enrico

Nice.

About the connection to the pins though, you didnt need a resistor?

Hi Mark,

It is your choice. It will function either way. Personally I would use it, because no components are perfect and it will look after your switch (provides a current limit - those small board switches might not handle much current), provides a bit of debounce (not that it should matter for a power-on circuit but anyway..)  (EDIT - also provides some protection if you accidentally connect the wire to an incorrect supply wire accidentally) - plus the original designers used it, so even if we cannot see their purpose it is harmless to add it.

But equally a body of engineers would just omit the resistor - there is not a lot of energy stored in that bit of circuit for example. So if it were a courtroom it would be a hung jury ; )

You can use any switch you like for the purposes of this button function, as long as it is a normally-open switch.

No, I have not used the resistor with a reason (not sure it is correct). Seeing in the scheme just as has suggested Shabaz in his post, my though is the following: If I should manage a push button with a GPIO port it is correct to use a resistor and eventually also a capacitor, just as the circuit in the scheme of these two buttons. But in this case the push button sends to GND exactly the signal pin "reset" and "system power" that - in the same Gizmo2 scheme - it is shown with a resistor capacitor etc. So I have excluded to add one more.

Pay attention as it is not sure that I am right

Enrico

If I should manage a push button with a GPIO port it is correct to use a resistor and eventually also a capacitor, just as the circuit in the scheme of these two buttons. But in this case the push button sends to GND exactly the signal pin "reset" and "system power" that - in the same Gizmo2 scheme - it is shown with a resistor capacitor etc. So I have excluded to add one more.

 

Not sure I understand.

For the record I don't mind using a resistor, it's a <$1 difference, I just wanted to test out right now if it works with my switch.