Safe way to provide external power to WF32

Created Tue, 03 Jun 2014 08:38:50 +0000 by benderamp

benderamp

Tue, 03 Jun 2014 08:38:50 +0000

Hello,

I have a number of Li-Po batteries I want to use to power ChipKIT Max32 board while it is connected with external USB device (Android smartphone):

• 7.4V 800mAh
• 14.8V 1550mAh

I have used both this batteries to power WF32 with blinking LED and it was OK.

But once I have connected Android tablet to USB host port while the board was powered with 14.8V battery and this damaged the board: it seems that FTDI module were burned out - the board stopped recognizing as COM-port on the laptop (so MPIDE could not work with it), but it was still alive - I could reflash and run it with PICkit3 and MPLAB. Nothing were connected to mini-USB UART.

As I remember WF32 had the following jumper config at that moment:

• J15.EXT=ON
• J15.UART=ON
• 5V regulator enabled: J16: IN-UV, OUT-5V0
• JP10=position A
• JP11=ON
• JP9=OFF

I suppose that JP9 (USB overcurrent detect)=OFF could be possible reason for that, but I don't feel very confident about this to risk another board to check this.

tom21091

Tue, 19 Jan 2016 17:50:54 +0000

Hi benderamp,

I was looking through some old unanswered posts and found your question here. I'm sorry that you never received an answer. In case anybody comes across this problem again, I think your FTDI chip was fried because of your JP15 settings. When you short both the UART and the EXT jumpers, this connects the two before being regulated to 5V. This means you sent 14.8V into the FTDI chip, which led to its demise. Only one jumper should be placed on JP15 at a time.

I hope this helps prevent somebody else from doing the same!

Tommy