Remora - Rpi Software Stepping Using External Microcontroller via SPI

The PRU is a small hardware in the Beaglebone Black, wich can generate pwm signals without using the BBB ressources. It’s like using an FPGA to generate steps.

...or like an integrated microcontroller

But PRU is cute and sounds like something new.

in that case I'm calling it Nouveau-PRU.
who knows maybe it might caught on / will catch on.

beagleboard.org/pru
It’s a 200mhz pwm dedicated processor. It’s more powerful than a LPC1768. It’s like a FPGA with hostmot2 firmware but with only pwm generation.

It’s easy to design this kind of chip since we have the hostmot2 firmware working in SPI, the only pb is the cost to produce it.

thanks.
for my use case, I like it modular
Remora's scalable to faster micro but of-course limited by the speed of SPI.
It's still a big jump from LP1768 72MHz to STM32F4 168MHz supposedly can
toggle pins at 84MHz if all you do is blink leds without actually seeing it blink
jeelabs.org/2018/toggling-io-pins/
As long as it does the job I wanted it to. (which so far not yet.)

forum.linuxcnc.org/18-computer/39037-lin...-pi-allwincnc#166968 is a similar project.
Many of the Allwinner ARM SOC's have an integrated microcontroller that they could have called a PRU but didn't. They instead kept it hidden for years and the memory space to access it was RE'd.
linux-sunxi.org/AR100
They connect to the big ARM cores internally over a high speed parallel bus. I forget the speed and width. I wish that the PRU's were actual FPGA's since we could do much more with them if they were.

Remora was originally called spiPRU and was first operational back in 2017 running with a RPi 3B which had so so real-time capabilities. Hence offloading the real time stuff to the "PRU".

Even though Remora is built on the Mbed framework there is no RTOS involved. It's still hard interrupt driven for most accurate timing. An RTOS on the LPC1768 can't even switch a thread at the frequencies we need for step generation.

Hey scotta has there been any more Hal work for the skr1.4 so the home inputs and bed output work?
thanks

has anyone pocked at the new RPI microcontroller? i heard a rumor the next pi will have it onboard so if it has any legs it might be worth looking at now for a more powerful solution of the allwinner

Cncninja wrote:

has anyone poked at the new RPI microcontroller? i heard a rumor the next pi will have it onboard so if it has any legs it might be worth looking at now for a more powerful solution of the allwinner