import pyb

accel = pyb.Accel() # create object of accelerometer

blue = pyb.LED(4) # create object of blue LED

log = open('1:/log.csv', 'w') # open file to write data - 1:/ ist the SD-card, 0:/ the internal memory

blue.on() # turn on blue LED

for i in range(100): # do 100 times (if the board is connected via USB, you can't write longer because the PC tries to open the filesystem which messes up your file.)

t = pyb.millis() # get time since reset

x, y, z = accel.filtered_xyz() # get acceleration data

log.write('{},{},{},{}\n'.format(t,x,y,z)) # write data to file

log.close() # close file

blue.off() # turn off LED