I should clarify. MCU could in theory use S-PWM (used in many MM drivers) to improve refresh rate. However this only works if you have low latency memory and DMA. The number of interrupts could become a massive problems.
Which could be resolved with the following:
- Low HUB75 speed
- Fast processor
- Long serial chain
In most cases this is too problematic due to stability concerns. This makes the most sense against a certain chain length and quality need. Very niche implementation. RPI likely will never be able to do this without significant effort.
Note BCM is technically possible with this but only helps with certain things. It lowers the amount of work and size of bit planes. However the number of interrupts is very high, if you waste refresh the number of interrupts can be kept low which helps with stability and frees time for other things.
You still have potential issues with BCM at LED driver layer with this approach. There is also an increase in overhead with this approach from dead time required between row switches potentially. (Aka ghosting prevention.)
It would be cool if someone added support for PWM/MM drivers but I have found using a receiver card directly is much more cost effective and offer better performance/quality. There are cases where this is not the case and I stand by my assertion that these are possible on the Pi and MCU. However only make sense in specific cases.
Note refresh is actually higher for S-PWM .