Pico W ENOMEM error when (re)using PIO (rp2_pio_init, CYW43)
First reported here: Pico W ENOMEM error when using PIO - Raspberry Pi Forums.
A program that uses PIO (such as the example code: micropython/pio_1hz.py at master · micropython/micropython) can't be reliably stopped and restarted on a Pico W, while it can on a Pico.
Expected result: being able to stop and start PIO example at will
Actual result: after a small number of attempts OSError: [Errno 12] ENOMEM
The cause appears to be identified as PIO.remove_program() not being usable when the CYW43 driver is loaded, as the CYW43 itself is running a PIO program.
Indeed, comments inside rp2_pio_init() suggest this may be an issue:
void rp2_pio_init(void) {
// Reset all PIO instruction memory.
#if MICROPY_PY_NETWORK_CYW43
// TODO: cannot reset PIO memory when CYW43 driver is enabled and active
// because it uses a PIO for the bus interface.
Version:
MicroPython v1.19.1 on 2022-07-29; Raspberry Pi Pico W with RP2040
rp2-pico-w-20220729-unstable-v1.19.1-223-g963e599ec.uf2
Raspberry Pi Pico2 W - Wifi fails to start if CPU is overclocked
Port, board and/or hardware
RPI_PICO_2_W
MicroPython version
MicroPython v1.25.0-preview.307.g4364d9411 on 2025-02-23; Raspberry Pi Pico 2 W with RP2350
Reproduction
Save the following code onto the Pico 2 W and run it with either CPU_FREQ = 300_000_000 or CPU_FREQ = 150_000_000 uncommented.
When using the overclocked frequency, the following error is printed and the access point is not available to connect to: [CYW43] Failed to start CYW43
When using the default frequency the access point can be connected to and no errors are printed
import machine
import network
"""
When overclocked we get
[CYW43] Failed to start CYW43
When using default CPU frequency
the wifi starts fine
"""
CPU_FREQ = 300_000_000 # overclocked
#CPU_FREQ = 150_000_000 # default
machine.freq(CPU_FREQ)
wifi = network.WLAN(network.WLAN.IF_AP)
wifi.config(
ssid="pico2w_ap",
channel=10,
security=network.WLAN.SEC_OPEN,
)
wifi.active(True)
Expected behaviour
WiFi should work if the CPU is overclocked
Observed behaviour
When the CPU is overclocked, the wireless card firmware does not appear to initialize correctly:
[CYW43] Failed to start CYW43
Additional Information
My testing setup has 2 I2C devices connected: an OLED display GP0 & GP1 and a battery-backed realtime clock on GP2 & GP3. The code above does not initialize these devices, so I don't think their presence should have any impact; it looks like simply changing the CPU frequency is enough.
Doing a little trial-and-error changing the frequencies in the script above it looks like 270MHz is the upper limit of what the wifi can handle. Is this a known limitation of the firmware?
Code of Conduct
Yes, I agree