Add simple datalogging example.

Author: tdicola

examples/datalogging.py

@@ -0,0 +1,52 @@
+# Simple GPS datalogging demonstration.
+# This actually doesn't even use the GPS library and instead just reads raw
+# NMEA sentences from the GPS unit and dumps them to a file on an SD card
+# (recommended) or internal storage (be careful as only a few kilobytes to
+# megabytes are available).  Before writing to internal storage you MUST
+# carefully follow the steps in this guide to enable writes to the internal
+# filesystem:
+#  https://learn.adafruit.com/adafruit-ultimate-gps-featherwing/circuitpython-library
+import board
+import busio
+
+
+# Path to the file to log GPS data.  By default this will be appended to
+# which means new lines are added at the end and all old data is kept.
+# Change this path to point at internal storage (like '/gps.txt') or SD
+# card mounted storage ('/sd/gps.txt') as desired.
+LOG_FILE = '/gps.txt'  # Example for writing to internal path /gps.txt
+#LOG_FILE = '/sd/gps.txt'     # Example for writing to SD card path /sd/gps.txt
+
+# File more for opening the log file.  Mode 'ab' means append or add new lines
+# to the end of the file rather than erasing it and starting over.  If you'd
+# like to erase the file and start clean each time use the value 'wb' instead.
+LOG_MODE = 'ab'
+
+# Define RX and TX pins for the board's serial port connected to the GPS.
+# These are the defaults you should use for the GPS FeatherWing.
+# For other boards set RX = GPS module TX, and TX = GPS module RX pins.
+RX = board.RX
+TX = board.TX
+
+# If writing to SD card customize and uncomment these lines to import the
+# necessary library and initialize the SD card:
+#SD_CS_PIN = board.SD_CS  # CS for SD card (SD_CS is for Feather Adalogger)
+#import adafruit_sdcard
+#spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
+#sd_cs = digitalio.DigitalInOut(SD_CS_PIN)
+#sdcard = adafruit_sdcard.SDCard(spi, sd_cs)
+#vfs = storage.VfsFat(sdcard)
+#storage.mount(vfs, '/sd')  # Mount SD card under '/sd' path in filesystem.
+
+# Create a serial connection for the GPS connection using default speed and
+# a slightly higher timeout (GPS modules typically update once a second).
+uart = busio.UART(TX, RX, baudrate=9600, timeout=3000)
+
+# Main loop just reads data from the GPS module and writes it back out to
+# the output file while also printing to serial output.
+with open(LOG_FILE, LOG_MODE) as outfile:
+    while True:
+        sentence = uart.readline()
+        print(str(sentence, 'ascii').strip())
+        outfile.write(sentence)
+        outfile.flush()