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# Generic lithium ion battery driver
from machine import Pin, ADC
class Battery(object):
def __init__(self, battery, charging, power=None):
self._battery = ADC(battery)
self._charging = charging
self._power = power
def charging(self):
return self._charging.value()
def power(self):
if self._power:
return self._power.value()
return self._charging.value()
def voltage_mv(self):
# Assumes a 50/50 voltage divider and a 3.3v power supply
raw = self._battery.read_u16()
return (2 * 3300 * raw) // 65535
def level(self):
# This is a trivial battery level estimation approach. It is assumes
# the discharge from 4v to 3.5v is roughly linear and 4v is 100% and
# that 3.5v is 5%. Below 3.5v the voltage will start to drop pretty
# sharply to we will drop from 5% to 0% pretty fast... but we'll
# live with that for now.
mv = self.voltage_mv()
level = ((19 * mv) // 100) - 660
if level > 100:
return 100
if level < 0:
return 0
return level
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