Firmware stripping

[techcatgato]

Hi! I am currently making my own modded firmware for specialized purpose. So far i've forced the gyro's high performance mode and overclocked the prime hub to 108MHZ. My question is - is there anything i can strip from the firmware to help save ram, flash and get calculations (floating point) done faster? or any other firmware level trick thats relevant for my case?

[dlech]

The Prime hub has plenty of free memory and flash space, so I wouldn't recommend disabling anything. The firmware only uses about 25% of the available resources and you would only stand to gain about another 5% by disabling things.

Also, be careful with the clock speed. In addition to the CPU, it affects all of the peripherals. In particular, this would break USB which requires exactly a 48MHz clock and could also mess up the baud rate on UART sensors (and less critically, the PWM frequencies).

What exactly are you wanting to do with this speed machine?

[techcatgato]

I'm running a loop that consists of odometry and path calculations and processing. There is a lil bit of logic but its mostly trig functions. I overclocked the hub to 108mhz currently and I noticed no problems while the trig and floating point operations seem to be 3% faster. Main reason I want to free up memory is to load big lookup tables to the ram to maybe save time on the math operation. With the current memory limit my tables can be 30% faster than traditional functions but I think this can be improved. Also, does increasing the wait States from 3 to 4 help keep a 48mhz usb clock?

[laurensvalk]

If you're building your own firmware anyway, you may be able to speed things up a lot more by doing some of your math in C, and leave things like clock speeds unchanged.

The actual math speed is the same, but the time savings will be in micropython not having to allocate any heap memory to do floating point math and do garbage collecting. It also saves time doing function lookups.

There is an existing hello_world example function for this in the pybricks.experimental module. It explains how to process arguments and return a result. In between, you can do anything you like. You can find it in pybricks/experimental.

[techcatgato]

Hey, Thanks ill look into that! Do you think i can get big speed gains or is it just a small improvement?

[techcatgato]

If you're building your own firmware anyway, you may be able to speed things up a lot more by doing some of your math in C, and leave things like clock speeds unchanged.

The actual math speed is the same, but the time savings will be in micropython not having to allocate any heap memory to do floating point math and do garbage collecting. It also saves time doing function lookups.

There is an existing hello_world example function for this in the pybricks.experimental module. It explains how to process arguments and return a result. In between, you can do anything you like. You can find it in pybricks/experimental.

How do i compile the firmware with pybricks.experimental included? Do I need some flag?

[laurensvalk]

It is already enabled on Primehub and Technic hub.

You can try the existing function:

from pybricks.experimental import hello_world

hello_world(123)