6 years, 10 months ago.

Getting strange data from analog input on Multitech Dragonfly (STM32)

I am trying to read battery voltage from an analog input on the dragonfly. The battery I am using has a header that regulates it at 5V, so I have power from the regulated side powering the dragonfly, and I have power and ground from the unregulated side of the battery header going to an analog input and common ground.

When the battery is fully charged, my multimeter says that the unregulated power has a charge of 4.175V, and the dragonfly reads around 0.86. The part that has me stumped is that, when the battery loses charge, the voltage readings on the dragonfly go up. So , when the battery is at 3.941v (and the battery still has between 50% and 70% of it's life left according to indicator lights on the battery), the dragonfly readings have gone up to 1, and will only report 1.00 until the battery dies.

start: multimeter-4.175V, dragonfly-0.86 (battery fully charged)

end: multimeter-3.941V, dragonfly-1.0 (3 of 4 battery indicator lights still on)

What am I doing wrong?