created SDdatalogger example

examples/SDdatalogger/datalogger.py

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+# datalogger.py
+# Logs the data from the acceleromter to a file on the SD-card
+
+import pyb
+
+# creating objects
+accel = pyb.Accel()
+blue = pyb.LED(4)
+switch = pyb.Switch()
+
+# loop
+while True:
+
+    # start if switch is pressed
+    if switch():
+        pyb.delay(200)                      # delay avoids detection of multiple presses
+        blue.on()                           # blue LED indicates file open
+        log = open('1:/log.csv', 'w')       # open file on SD (SD: '1:/', flash: '0/)
+
+        # until switch is pressed again
+        while not switch():
+            t = pyb.millis()                            # get time
+            x, y, z = accel.filtered_xyz()              # get acceleration data
+            log.write('{},{},{},{}\n'.format(t,x,y,z))  # write data to file
+
+        # end after switch is pressed again
+        log.close()                         # close file
+        blue.off()                          # blue LED indicates file closed
+        pyb.delay(200)                      # delay avoids detection of multiple presses