Allow sending less than the whole array in PulseOut.send

[dmcomm]

Requiring the array.array to be exactly the right length means that if the messages have different numbers of pulses, there's going to be a lot of memory reallocation going on, potentially on quite large objects. An optional count argument would allow reuse of the same memory allocation for each message.

[deshipu]

I wonder, can you use memoryview and slices to work around this?

[dmcomm]

I wonder, can you use memoryview and slices to work around this?

Can you create two Array with the same backing buffer? Though if you can, that would risk making really hard-to-trace bugs if you accidentally trigger a resizing operation.

Looks like PulseOut.send checks for an object having typecode == 'H', otherwise raising TypeError: Array must contain halfwords (type 'H'). Then it checks for buffer protocol, otherwise raising TypeError: object with buffer protocol required. Not sure if there's anything could be done with that.

...

Indeed this appears to be possible, but may not be a good idea ;)

import array
import board
import time
import pulseio
import pwmio

pwm = pwmio.PWMOut(board.GP0, frequency=38000, duty_cycle=2**15)
pulseOut = pulseio.PulseOut(pwm)

class MyMemoryView(memoryview):
    pass

pulses = array.array('H', [1000,1000,2000,1000,3000,1000,4000])

m1 = memoryview(pulses)
m2 = m1[:4]
m3 = MyMemoryView(m2)
m3.typecode = "H"  #this is not allowed on a memoryview, but is allowed on subclasses

while(True):
    pulseOut.send(m3)
    time.sleep(5)