import pyb, array, micropython

N_SECONDS=12		# How many seconds to collect data for
SAMPLE_FREQ=1000	# 1000 samples/sec for the ADC
NSAMPLES =SAMPLE_FREQ * N_SECONDS
PIN = pyb.Pin.board.X1	# Which pin to read input data from

def cb(timer):
    global adc, n_reads, vals

    if (n_reads<NSAMPLES):
        vals [n_reads] = adc.read()
        n_reads += 1
    else:
        timer.deinit()

# This function merely calls cb(). Why bother? Because cb_irq is an interrupt
# handler and can only have very restricted functionality. Calling a regular
# function via schedule() removes all restrictions.
def cb_irq(timer):
    micropython.schedule (cb, timer)

def main():
    #print ("hello")
    micropython.alloc_emergency_exception_buf(100)

    global vals, adc, n_reads, PIN
    n_reads=0

    # Allocate the buffer that we store data into at 1kHz. Storing into a
    # buffer is fast and easy to do at 1kHz; then we'll save it to the flash
    # drive (which is slow) later. 
    vals  = array.array('H', (0 for _ in range(NSAMPLES)))	# 2B/entry

    # Set up the ADC on the requested pin; its digital output range is [0,4095]
    adc = pyb.ADC(PIN)
    print ("Done with ADC setup")

    # Set up the timer.
    tim = pyb.Timer(4)
    tim.init(freq=SAMPLE_FREQ, callback=cb_irq)
    print ("Setup timer")

    # Tim.init() above is non-blocking, and so returns immediately.
    # Use this infinite loop to wait until we've collected all the samples.
    pyb.LED(2).on()	# Green LED while we're capturing
    while n_reads < NSAMPLES:
        pass
    pyb.LED(2).off()
    print ("Done sampling")

    pyb.LED(1).on()	# Red LED while we're saving to a file.
    with open('data.csv','w') as f:
        for i in range(NSAMPLES):
            f.write("{}\n".format(vals[i]))
    pyb.LED(1).off()
    print ("Done writing data1")

main()