40 lines
1.2 KiB
Python
40 lines
1.2 KiB
Python
# SPDX-License-Identifier: LGPL-3.0-or-later
|
|
# Copyright (C) 2020 Daniel Thompson
|
|
|
|
# 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
|