pimoroni-pico/micropython/examples/badger2040/battery.py

164 lines
4.5 KiB
Python

import badger2040
from machine import Pin, ADC
import time
# Global Constants
# for e.g. 2xAAA batteries, try max 3.4 min 3.0
MAX_BATTERY_VOLTAGE = 4.0
MIN_BATTERY_VOLTAGE = 3.2
WIDTH = badger2040.WIDTH
HEIGHT = badger2040.HEIGHT
BATT_WIDTH = 200
BATT_HEIGHT = 100
BATT_BORDER = 10
BATT_TERM_WIDTH = 20
BATT_TERM_HEIGHT = 50
BATT_BAR_PADDING = 10
BATT_BAR_HEIGHT = BATT_HEIGHT - (BATT_BORDER * 2) - (BATT_BAR_PADDING * 2)
BATT_BAR_START = ((WIDTH - BATT_WIDTH) // 2) + BATT_BORDER + BATT_BAR_PADDING
BATT_BAR_END = ((WIDTH + BATT_WIDTH) // 2) - BATT_BORDER - BATT_BAR_PADDING
NUM_BATT_BARS = 4
# ------------------------------
# Utility functions
# ------------------------------
def map_value(input, in_min, in_max, out_min, out_max):
return (((input - in_min) * (out_max - out_min)) / (in_max - in_min)) + out_min
# ------------------------------
# Drawing functions
# ------------------------------
# Draw the frame of the reader
def draw_battery(level, resolution):
display.pen(15)
display.clear()
display.thickness(1)
# Draw the battery outline
display.pen(0)
display.rectangle(
(WIDTH - BATT_WIDTH) // 2, (HEIGHT - BATT_HEIGHT) // 2, BATT_WIDTH, BATT_HEIGHT
)
display.rectangle(
(WIDTH + BATT_WIDTH) // 2,
(HEIGHT - BATT_TERM_HEIGHT) // 2,
BATT_TERM_WIDTH,
BATT_TERM_HEIGHT,
)
display.pen(15)
display.rectangle(
(WIDTH - BATT_WIDTH) // 2 + BATT_BORDER,
(HEIGHT - BATT_HEIGHT) // 2 + BATT_BORDER,
BATT_WIDTH - BATT_BORDER * 2,
BATT_HEIGHT - BATT_BORDER * 2,
)
# Add a special check for no battery
if level < 1:
X = WIDTH // 2
Y = HEIGHT // 2
display.pen(0)
display.thickness(1)
thickness = (BATT_BORDER * 3) // 2
start_extra = thickness // 3
end_extra = (thickness * 2) // 3
for i in range(0, thickness):
excess = i // 2
display.line(
X - (BATT_HEIGHT // 2) + i - excess - start_extra,
Y - (BATT_HEIGHT // 2) - excess - start_extra,
X + (BATT_HEIGHT // 2) + i - excess + end_extra,
Y + (BATT_HEIGHT // 2) - excess + end_extra,
)
display.pen(15)
for i in range(0 - thickness, 0):
display.line(
X - (BATT_HEIGHT // 2) + i,
Y - (BATT_HEIGHT // 2),
X + (BATT_HEIGHT // 2) + i,
Y + (BATT_HEIGHT // 2),
)
else:
# Draw the battery bars
display.pen(0)
length = (
BATT_BAR_END - BATT_BAR_START - ((NUM_BATT_BARS - 1) * BATT_BAR_PADDING)
) // NUM_BATT_BARS
current_level = 0.0
normalised_level = level / resolution
for i in range(NUM_BATT_BARS):
current_level = (1.0 * i) / NUM_BATT_BARS
if normalised_level > current_level:
pos = i * (length + BATT_BAR_PADDING)
display.rectangle(
BATT_BAR_START + pos,
(HEIGHT - BATT_BAR_HEIGHT) // 2,
length,
BATT_BAR_HEIGHT,
)
display.update()
# ------------------------------
# Program setup
# ------------------------------
# Create a new Badger and set it to update FAST
display = badger2040.Badger2040()
display.update_speed(badger2040.UPDATE_FAST)
# Set up the ADCs for measuring battery voltage
vbat_adc = ADC(badger2040.PIN_BATTERY)
vref_adc = ADC(badger2040.PIN_1V2_REF)
vref_en = Pin(badger2040.PIN_VREF_POWER)
vref_en.init(Pin.OUT)
vref_en.value(0)
# ------------------------------
# Main program loop
# ------------------------------
last_level = -1
while True:
# Enable the onboard voltage reference
vref_en.value(1)
# Calculate the logic supply voltage, as will be lower that the usual 3.3V when running off low batteries
vdd = 1.24 * (65535 / vref_adc.read_u16())
vbat = (
(vbat_adc.read_u16() / 65535) * 3 * vdd
) # 3 in this is a gain, not rounding of 3.3V
# Disable the onboard voltage reference
vref_en.value(0)
# Print out the voltage
print("Battery Voltage = ", vbat, "V", sep="")
# Convert the voltage to a level to display onscreen
level = int(
map_value(vbat, MIN_BATTERY_VOLTAGE, MAX_BATTERY_VOLTAGE, 0, NUM_BATT_BARS)
)
# Only draw if the battery level has changed significantly
if level != last_level:
draw_battery(level, NUM_BATT_BARS)
last_level = level
time.sleep(1)