Auto power-on with battery only

zawie

I’ve got a question about power management on the design…

If the feather is connected by battery via the onboard 2-pin, JST connector, it requires the MODE button to be pressed to power on.

Is there anyway to make it auto-power on, when the battery is connected without having to press MODE ?

Tying EN to 0V or BAT doesn’t seem to do the trick. Also, tying MODE to BAT, although that works, the mode button (for entering DFU) ceases to work, it also shorts the switch and the MODE switch.

Only other possible is the RTC, but as that’s off when the battery is disconnected, I’m guessing it would lose it’s settings. I’m sure I’m missing something somewhere.

jaredwolff

zawie Is there anyway to make it auto-power on, when the battery is connected without having to press MODE ?

The MD pin will be able to do this in the next rev but it's hooked up to the mode/wake switch.

zawie Tying EN to 0V or BAT doesn’t seem to do the trick. Also, tying MODE to BAT, although that works, the mode button (for entering DFU) ceases to work, it also shorts the switch and the MODE switch.

The enable pin is only used to shutdown at the moment due to the way I designed the enable circuitry. As for the bootloader, it does need a longer delay before going into "bootloader mode". The fix for this is to hit the reset button after pressing the mode button to wake up. (It will remain powered but start executing your code)The next version of the BL will have the delay fix.

Another way to wake up the nRF9160 Feather is to briefly insert USB. You could place a momentary switch from VBAT to USB to turn it on. I wouldn't advise leaving it shorted for a long duration of operation due to leakage. The charger shouldn't do anything once VDC is < 4.25V. That doesn't mean it won't though. 😉

zawie

jaredwolff What do you think about Cutting the Mode track and then botch wiring from U9 to VSYS ?

I'm figuring this should isolate the MODE switch but still leave it working, and also enables the power supply from battery when connected without increasing leakage? Any unintended consequences?

jaredwolff

You can do that or you can cut the NRF_PS_EN trace as well if you want the exact functionality.

I'll be adding a jumper in the next rev of the board so folks can set this permanently if they want.

zawie

jaredwolff Doh, yes that's a better approach, it appears the TPS63031 doesn't have an internal pullup, so... what I did is remove R5 (instead of cutting the track, and solder a very short piece of wirewrap between the top of C6 and the R5 pad. Just about the right distance for an 0402 0 ohm jumper to fit in that gap instead of wire wrap too.

Now I'll just need to figure out how to instruct a complete newb on how to do that for the 3 prototypes I sent out :-)