All state machines in use for more than two PIO on Pi Pico

[kevinjwalters]

On Adafruit CircuitPython 6.2.0-beta.2-18-g2a467f137 on 2021-02-15 this code spits a RuntimeError: All state machines in use

import time

import board
import rp2pio
import adafruit_pioasm

print("15 second pause in case anything bad happens")
time.sleep(15)


flash_pio_code_2pin = """
.program flash2
    set x, 31
onloop:
    set pins, 3  [5]
    jmp x-- onloop

    set y, 31
offloop:  
    set pins, 0  [5]
    jmp y-- offloop
"""

flash_pio_code_3pin = """
.program flash3
    set x, 31
onloop:
    set pins, 7  [5]
    jmp x-- onloop
    set y, 31
offloop:  
    set pins, 0  [5]
    jmp y-- offloop
"""

flash_pio_code_4pin = """
.program flash4
    set x, 31
onloop:
    set pins, 15  [5]
    jmp x-- onloop

    set y, 31
offloop:  
    set pins, 0  [5]
    jmp y-- offloop
"""

KILLER_THIRD = True
KILLER_FOURTH = False
MIN_FREQUENCY=1908

sm1 = rp2pio.StateMachine(
    adafruit_pioasm.assemble(flash_pio_code_2pin),
    init=adafruit_pioasm.assemble("set pindirs {:d}".format(2**2 - 1)),
    frequency=MIN_FREQUENCY,
    first_set_pin=board.GP0,
    set_pin_count=2,
)

sm2 = rp2pio.StateMachine(
    adafruit_pioasm.assemble(flash_pio_code_2pin),
    init=adafruit_pioasm.assemble("set pindirs {:d}".format(2**2 - 1)),
    frequency=MIN_FREQUENCY,
    first_set_pin=board.GP3,
    set_pin_count=2,
)

if KILLER_THIRD:
    sm3 = rp2pio.StateMachine(
        adafruit_pioasm.assemble(flash_pio_code_3pin),
        init=adafruit_pioasm.assemble("set pindirs {:d}".format(2**3 - 1)),
        frequency=MIN_FREQUENCY,
        first_set_pin=board.GP8,
        set_pin_count=3,
    )

if KILLER_FOURTH:
    sm4 = rp2pio.StateMachine(
        adafruit_pioasm.assemble(flash_pio_code_4pin),
        init=adafruit_pioasm.assemble("set pindirs {:d}".format(2**4 - 1)),
        frequency=MIN_FREQUENCY,
        first_set_pin=board.GP11,
        set_pin_count=4,
    )

time.sleep(30)

Based on discussion in Adafruit Forums: Can RP2040 PIO PULL be used in CircuitPython? this should work either due to code sharing or packing code into shared memory.

[kevinjwalters]

FYI, I think code sharing kicks in based on the assembed code object, sm1 and sm2 would need to refer to same assembled code to do this.

Unrelated, elite users with 32 bytes of pio code may get a disappointment: raspberrypi/pico-sdk#261

[dhalbert]

I'm closing this because #4405 does fix it. I ran the test program above without error.