2Threads

The Pi PICO allows you to run two programs simultaneously. Each is actually called a "Thread" and both are stored in the same Python file.
When started, the Pico runs Thread 1, and you have to put in a command in thread 1 to run a function as the second thread:

The advantage of this is that the second thread can be scanning inputs very fast, so that inputs are not missed during pauses, or long calculations in the first thread.

A sample program using two threads is Drag5 (view txt)
the first thread reads the pushbutton and line sensors, , and runs the motors. It starts thread2 running as required.
the second thread constantly scans the stop sensor at high speed and counts how many have been seen.

Starting the second thread

The code for the second thread is coded as a function:

def Thread2():
    global Markers,ClearCount,MarkerMs
    print("Th2 starting")
    while True:
        ssense = reads(stopsense.read_u16())     # read stop sensor
        while (ssense < 60):
            ssense = reads(stopsense.read_u16()) # read stop sensor
            time.sleep(.001)
            if (ClearCount == True   ):     # if flag set
                ClearCount = False          # clear flag
                Markers = 0                 # reset count
        # marker started...... increment count
        Markers += 1
        tstart = time.ticks_ms()            # record start time
        while (ssense >40):
            ssense = reads(stopsense.read_u16()) # read stop sensor
            time.sleep(.001)
            if (ClearCount == True   ):
                ClearCount = False
                Markers = 0 
        MarkerMs=time.ticks_diff(time.ticks_ms(),tstart)    # record length
        ## marker ended
        time.sleep(.001)

This is the code to start the second thread.
It must be included in the main thread.

_thread.start_new_thread(Thread2, ())