`MCU 'mcu' shutdown: Timer too close` on print start

[flaviut]

In the couple weeks or so since I've installed this I've seen this error about 3 times, always immediately after sending a print over from Orcaslicer via the API:

// MCU 'mcu' shutdown: Timer too close
// This often indicates the host computer is overloaded. Check
// for other processes consuming excessive CPU time, high swap
// usage, disk errors, overheating, unstable voltage, or
// similar system problems on the host computer.
// Once the underlying issue is corrected, use the
// "FIRMWARE_RESTART" command to reset the firmware, reload the
// config, and restart the host software.
// Printer is shutdown

The resolution is simple, just restart Klipper and restart the print job, but this is annoying.

I suspect this has something to do with the CPU speed, which seems to sit at 600MHz most the time. I don't see any processes using a significant amount of CPU otherwise.

The default CPU governor is ondemand, which is configured to check the system load every 200ms. I suspect this could be the issue, Klipper all the sudden starts demanding more of the system, and the system falls behind before it realizes it needs to bump things up. I'm hoping that switching the governor to schedutil, which should hopefully respond instantly, will work:

$ cat /etc/systemd/system/cpufreq-tuning.service 
[Unit]
Description=Set CPU governor

[Service]
Type=oneshot
ExecStart=/bin/bash -c 'for d in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do echo schedutil > "$d"; done'

[Install]
WantedBy=multi-user.target
$ sudo systemctl enable --now cpufreq-tuning.service

[t-e-u]

i had the same issue during execution COMPARE_BELTS_RESPONSES
i will try your fix to solve this problem...

[MicroSur]

There is no positive effect.

[t-e-u]

There is no positive effect.

I switched to FreeDi firmware and it works great, try it instead of OpenQ1.

[flaviut]

There is no positive effect.

Agreed. Even CPU pinning doesn't work.

I'm currently trying to add the following to the end of the [gcode_macro PRINT_START] macro, hopefully it will work:

    # Slow travel toward the print area primes ~5s of move buffer, giving the
    # 250kbaud toolhead link transmission headroom before the dense first-layer
    # burst (avoids "Stepper too far in past" on resume from the M109 dry-buffer).
    G90
    G1 X120 Y220 F600

I switched to FreeDi firmware

My whole goal is to only use Free Software. FreeDi is unfortunately non-free and also violates Klipper's license.