Output voltage on XAIO nRF52840 only 0.5v

Products & Technology
#1

Hi,

I have recently got a XAIO nRF52840 and want to power it with a 3.3v lipo. I have connected the terminals on the base of the unit. When I measure the output on pin 11 (3.3v) I am only showing 0.5v. The battery is outputting 3.6v so fully charged. When I plug in the USB C lead it starts to charge the attached battery and the output on pin 11 goes up to 3.3v. Charging Output 4.15v.

Am I connecting to the wrong output? I want to power a sensor that needs 3.3v. But why is the output only 0.5v on pin 11? What am I doing wrong?

Thanks

Bob

#2

Does XIAO work with only a charged battery without USB connection?
Is “pin 11” “3.3V”? or “D10”?

#3

Hi,

Thanks for the reply. The XAIO doesn’t seem to work with the battery connected. I tried the Blink sketch with the battery connected and with the usb. It only blinks when the usb is connected. The pin I am connecting to is the 3rd pin down from top right. 5v GND 3.3v. I do get 3.3v output when the usb is connected but not the battery. The green charge led comes on when connected to the lipo battery and usb, and it does charge the battery. I then removed the usb and changed the battery to 3 x AA (4.5v) and the same readings. 0.49v on the 3.3v output and no blinking.

Without a battery connected and the usb connected the blink works and I’m getting 3.98v charging current on the battery terminals. So something weird going on.

Thanks

#4

3 x AA (4.5v)

  1. What kind of battery do you have connected, a lipo battery?
  2. Can the battery be charged properly with other chargers?
  3. And does it get 4.2V when fully charged?
  4. What is the voltage of the battery removed from XIAO?
#5

1 I have used 2 types of battery. 1 x 3.7v 18650 lipo and non rechargable 3 x AA total 4.5v.
2 Yes the lipo charges normally when charged separately.
3 Yes it reached 4.15v after charging.
4. The voltage for the lipo is 3.5 and for the AA 4.5v.

Without the battery connected the voltage to the battery leads is 3.9v

Clearly something is blocking the voltage going back to the XAIO. I’m thinking a faulty diode or such like?

Thanks

Bob

#6

As you can see from the schematic on the Wiki page, it is very possible that the p-channel MOS switch circuit that automatically switches from USB 5V to a battery is not working.

#7

That sounds very likely and explains why I get the same result with two types of battery input. I will put in a support ticket to where I purchased it.

Thanks for your help.

Bob