Power board via ext connector

[morind79]

Hi All,

I have a question concerning powering the board, is it possible to only supply +5V on the GPIO connector ?
I see in the schematic there is "5V_E Open", should I close it ?

Thanks

Best regards
Denis

[JohnS]

The CPU cannot handle 5V.  Never put 5V on any of its pins.

John

[morind79]

Hi JohnS,

I do not apply +5V on the CPU pins, but want to apply +5V on the GPIO connector (Ex on the GPIO-1 connector).
I see this +5V go to +5V delivered by U14 (MP1482DS), but then there is a jumper 5V_E and I think I should close it to have 5VEXT set to +5V too.
Just want confirmation :-)

Best regards
Denis

[dave-at-axon]

From what I can see this is not an external 5V input as such. From reading the schematic 5V_EXT is referring to the external 5V coming from the switch mode supply from the 6-16V DC input.

The link is OPEN because there is a diode in parallel with this allowing forward flow of the external 5V to the circuit. In normal operation with external power, the 5V is supplied via this diode. The high GATE input to the FET ensures that this is switched off so therefore the battery is not providing power to the circuit.

When external power is removed, the GATE input goes low, switching on the FET so that the battery now powers the device.

If you apply 5V direct to the GPIO connector, you then have both it and battery (if you have one) supplying the board all the time. If you have no battery then it might work but leave 5V_E open so that the diode will block your 5V from reaching U14.

[morind79]

Hi Dave,

I leaved it open, but does not work.
in fact i think the issue is that U12 is not powered with the 5VEXT connected to its 32 and 33 pin ?

What do you think ?

Best regards
Denis

[dave-at-axon]

Ah yes, I missed the connection with the AXP209.

Looks like your only option is to use an external power supply. I used 12V as it's very common.

[morind79]

All right, but I should use something connected to the GPIO port to power up the board.
What is the risk if I close the 5V_E jumper and apply +5 on the GPIO ?
I think it is not an issue for U14, but would like to have confirmation, otherwise I should unsolder it

Best regards
Denis

[dave-at-axon]

If you are going to unsolder U14, why not do this and link the INPUT to OUTPUT pads on this now removed IC?

Is there a reason you want to power from the GPIO connector?

[morind79]

Well unsoldering it seems to be quite difficult, I would like to avoid it, I will try to close this jumber 5V_E and see what happen, I do not thing this will be a problem for U14.

Br
Denis

[morind79]

I reply to myself if this can help other people,
I have unsoldered U14 and closed 5V_E, everything is working fine so yes, I am able to power up Olinuxino A20 with +5V applied on the GPIO connector.

Here is OliExt board I used : https://github.com/morind79

Best regards
Denis