I am so frustrated with this problem, please help me if anyone knows whats happening here..

I am using pigpio in python 2.7/raspberry pi. the purpose is to control three devices over serial. It works well when I do step by step but somehow multiprocesing messes up something. I’ve tried to use multiprocessing with Lock, but it seems doesn’t help at all.

def pjt_bright(pjt_n,brightness): # PJT[x], brightness : 0-1000
    fade_nr=bytearray.fromhex('{:02x}'.format(249)+'{:02x}'.format(16+(brightness//128)*2)+'{:02x}'.format((brightness%128)*2))
    #print "fade number      =    ",brightness,"       projector nr    =      ", pjt_n
    pi.wave_clear()
    pi.wave_add_serial(pjt_n, BAUD, fade_nr)
    time.sleep(0.1)
    faderun=pi.wave_create()
    pi.wave_send_once(faderun)

def pjt_fade1(pjt_n,flag,gap,lock): #MAX 50 MIN -2sec min 3
        with lock:
            pjt_bright(pjt_n,0)
        for i in range(1000//gap):
            with lock:
                b=i*gap
                pjt_bright(pjt_n, b) #int|(i*gap)
                time.sleep(0.15)
        time.sleep(2) #top notch and will go fade down
        for i in range(1000//gap,-1,-1):
            with lock:
                b=i*gap
                pjt_bright(pjt_n, b) #int|(i*gap)
                time.sleep(0.15)

And the actual call happens

fading1=multiprocessing.Process(target=pjt_fade1, args=[PJT[1],1,int(round(np.interp(idx_s[1][0],[0,9],[10,41]))),lock])

the error messages, it really depends but usually

`File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 2275, in wave_create
    return _u2i(_pigpio_command(self.sl, _PI_CMD_WVCRE, 0, 0))
      File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 979, in _u2i
        raise error(error_text(v))
    error: 'attempt to create an empty waveform'`