Expected step rate using F446

[fitch22]

What is an expected step rate achievable with an Nucleo F446? I am using whatever default settings there are (internal clock). It looks like the cpu clock gets set to 180MHz. I have $0=2, $110=999999, and $120=100000. The best I seem to get is about 125KHz just moving a single axis. I thought I saw a picture of someone else with an F446 getting around 400KHz.

Am I doing something wrong? Is there a setting I missed that affects this? Ultimately I need to drive 3 axis, so I just need a target number. It is possible I need a faster MCU than the F446.

Thanks.

[terjeio]

The best I seem to get is about 125KHz

When you try to go above that what happens?
I just scoped the F446 to ~330KHz with $100=300, $110=50000 and $120=1000. There is some visible jitter, I do not know if step pulses are lost - to check that I have to set up the simulator. At least the DRO ends up in the commanded position.
BTW - do not set $110 to a value that would give you step rates in excess on what you target and what the MCU is capable of.

Is there a setting I missed that affects this?

$398 (planner buffer blocks) may affect max. step rate - try reducing it to 35 which was the old default value. Acceleration must be high if you want to end up at high speeds within a reasonable distance.

[fitch22]

@terjeio Thank you. I found by changing my steps/mm I could easily get over 300KHz, so I am very happy with this. My target is 200KHz, I should have good headroom with this processor.