Qt Py SAMD21 lipoly charger question

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christofeugster
 
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Joined: Sun Jan 02, 2022 2:46 am

Qt Py SAMD21 lipoly charger question

Post by christofeugster »

Hi Guys

Im in hurry to complete a gift for my nice.
Im using a Qt Py SAMD21 and a lipoly charger. Unfortunately not the new one specially for qt py.
Its the Adafruit LiIon/LiPoly Backpack Add-On for Pro Trinket/ItsyBitsy.
Well i can use it but have some troubles.
-Im connecting Qt Py 5V out - to 5V on Charger, Ground to ground - Lipo is charging when plug in USB.
-Now i want to use lipo power back to Qt Py, so i tryed to use the Qt 5V pin as input. With a diode of course. - the board does boot and i have around 4.2V on 3.3V regulated out. But the connected sensor with a signal line is not powered but i measuring Voltage?
- The only way its working (kind off) is, when i connect BAT from Charger directly to 3.3V of Qt Py. I then have regulated Power (Lipo Voltage) but the system is unstable.
And, as soon as i disconnect the battery (switch) with USB unplugged, and reconnect battery, i have to reboot the board before its working again. Thats bad, as i dont want to explain my nice to allways open up the case to hit
reset button.
-I also tried BAT to 5V (diode) and BAT to 3.3V (diode) but this doesent work as well. Most likely because the Voltage drop of the diode lowers 3.3V to 3V

Has anybody a working example on how to correctly wire those two with working regulated 3.3V out?

Thanks guys

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