Now that we know where to get the current (lat, lon) for the ISS and how to convert that to (x, y) we can write a little program to display this in near real time. The general idea for the program is pretty simple:
- Load a background map (map.bmp)
- Every ~10 seconds:
- Get the current (lat, lon) location
- Compute screen (x, y) from (lat, lon)
- Draw a marker at (x,y)
- Add location trail
That's it.
Download the Project Files
Here's the complete code that does this. Click on the Download Project Bundle button to get all the files for this project:
# SPDX-FileCopyrightText: 2019 Carter Nelson for Adafruit Industries
#
# SPDX-License-Identifier: MIT
import time
import math
import board
import displayio
from terminalio import FONT
from adafruit_pyportal import PyPortal
from adafruit_display_shapes.circle import Circle
from adafruit_display_text.label import Label
#--| USER CONFIG |--------------------------
MARK_SIZE = 10 # marker radius
MARK_COLOR = 0xFF3030 # marker color
MARK_THICKNESS = 5 # marker thickness
TRAIL_LENGTH = 200 # trail length
TRAIL_COLOR = 0xFFFF00 # trail color
DATE_COLOR = 0x111111 # date color
TIME_COLOR = 0x111111 # time color
LAT_MAX = 80 # latitude (deg) of map top/bottom edge
UPDATE_RATE = 10 # update rate in seconds
#-------------------------------------------
DATA_SOURCE = "http://api.open-notify.org/iss-now.json"
DATA_LOCATION = ["iss_position"]
WIDTH = board.DISPLAY.width
HEIGHT = board.DISPLAY.height
# determine the current working directory needed so we know where to find files
cwd = ("/"+__file__).rsplit('/', 1)[0]
pyportal = PyPortal(url=DATA_SOURCE,
json_path=DATA_LOCATION,
status_neopixel=board.NEOPIXEL,
text_font=None,
default_bg=cwd+"/map.bmp")
# Connect to the internet and get local time
pyportal.get_local_time()
# Date and time label
date_label = Label(FONT, text="0000-00-00", color=DATE_COLOR, x=165, y=223)
time_label = Label(FONT, text="00:00:00", color=TIME_COLOR, x=240, y=223)
pyportal.splash.append(date_label)
pyportal.splash.append(time_label)
# ISS trail
trail_bitmap = displayio.Bitmap(3, 3, 1)
trail_palette = displayio.Palette(1)
trail_palette[0] = TRAIL_COLOR
trail = displayio.Group()
pyportal.splash.append(trail)
# ISS location marker
marker = displayio.Group()
for r in range(MARK_SIZE - MARK_THICKNESS, MARK_SIZE):
marker.append(Circle(0, 0, r, outline=MARK_COLOR))
pyportal.splash.append(marker)
def get_location(width=WIDTH, height=HEIGHT):
"""Fetch current lat/lon, convert to (x, y) tuple scaled to width/height."""
# Get location
try:
location = pyportal.fetch()
except RuntimeError:
return None, None
# Compute (x, y) coordinates
lat = float(location["latitude"]) # degrees, -90 to 90
lon = float(location["longitude"]) # degrees, -180 to 180
# Scale latitude for cropped map
lat *= 90 / LAT_MAX
# Mercator projection math
# https://stackoverflow.com/a/14457180
# https://en.wikipedia.org/wiki/Mercator_projection#Alternative_expressions
x = lon + 180
x = width * x / 360
y = math.radians(lat)
y = math.tan(math.pi / 4 + y / 2)
y = math.log(y)
y = (width * y) / (2 * math.pi)
y = height / 2 - y
return int(x), int(y)
def update_display(current_time, update_iss=False):
"""Update the display with current info."""
# ISS location
if update_iss:
x, y = get_location()
if x and y:
marker.x = x
marker.y = y
if len(trail) >= TRAIL_LENGTH:
trail.pop(0)
trail.append(displayio.TileGrid(trail_bitmap,
pixel_shader=trail_palette,
x = x - 1,
y = y - 1) )
# Date and time
date_label.text = "{:04}-{:02}-{:02}".format(current_time.tm_year,
current_time.tm_mon,
current_time.tm_mday)
time_label.text = "{:02}:{:02}:{:02}".format(current_time.tm_hour,
current_time.tm_min,
current_time.tm_sec)
try:
board.DISPLAY.refresh(target_frames_per_second=60)
except AttributeError:
board.DISPLAY.refresh_soon()
# Initial refresh
update_display(time.localtime(), True)
last_update = time.monotonic()
# Run forever
while True:
now = time.monotonic()
new_position = False
if now - last_update > UPDATE_RATE:
new_position = True
last_update = now
update_display(time.localtime(), new_position)
time.sleep(0.5)
Plug your PyPortal into your computer with a known good USB data+power cable.
Copy all the files from the zip file on your computer to the PyPortal with the subdirectories noted below.
Your PyPortal CIRCUITPY drive should contain the following files in the correct folders:
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