I have a problem with the build in battery charger. My boron is connected to a main board. From the main board i receive over UART data packages. There are additional 5V and GND connections between them. On the 5V line is a diode, to make sure the main board can’t draw current from the battery which is connected to the boron. The problem now is, that after the diode only 4.2V are applied on the VUSB pin, which is not enough for the battery charger to charge the battery.
In the boron datasheet I couldn’t find a voltage range the charger at least needs?
Second question is, if I add a voltage divider after the 5V line to get 3.3V can I use this as an wakeup interrupt? So as soon as the main board get’s turned on, my particle will wake up to send the newest data?
BTW, when you power your device off of LiPo you will not see any voltage on VUSB.
So the risk of powering your main board off the LiPo is not actually an issue
But before I was using the diode the main board didn’t turned off by using it main switch. That’s a strange behavior i guess.
Another strange thing: the battery is unplugged and the board is connected to the 5V line and even when both systems are off the particle boron draws 10mA which will discharge the battery of the main board in a while. I have an STH31-D temperature sensor connected to the 3.3V pin of the boron, but when the boron is off there should not be any current draw, right?
Even when the Boron is in sleep mode, the onboard regulators will not be switched off and hence anything feeding from the 3v3 pin will also be powered.
I have another question, is it possible to switch between the connected battery and the VUSB+ as the main power supply? My main board also has an battery which is going to discharge to quickly even if the boron is on sleep. I made a measurement of the current which is drawn from the battery (connected to the boron) while my main board supplies these 5V and its only around 9 microA. So the main current is drawn from the main board (40-70 mA). I already realized that my battery only gets charged when the main board is connected to a charger.