Remora - Rpi Software Stepping Using External Microcontroller via SPI

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12 Dec 2021 20:36 #228946 by blazini36

You already found the other thread for the Teensy 4.1 forum.linuxcnc.org/18-computer/43212-teensy-based-cnc-board

Nobody has publicly posted their intentions or code for the Teensy 4.1 yet. Just questions and some info about it so far.
 

Do you contribute to Remora, or do you just love to post?

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12 Dec 2021 22:14 #228952 by cakeslob
so, as I understand remora, the iMXrt1062 is not supported by mbedOS, so its probably a non-starter. the imxrt-1050 is supported, and there were a few threads on teensy forum about support for 4.0, but thats about it. you could probably use the remora.comp with your own custom non mbedos firmware, but you could do that with other spi comps also. But the main thing going on as I understand it, is that the remora firmware is based on mbedos framework.

Anyone recognise this board? It has SD card and Ethernet.

 

from what I found, it is a generic stm32 dev board from china, but that looks like an older revision because none of the ones I found look exactly like that, but similar with same features

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12 Dec 2021 22:46 #228953 by blazini36

so, as I understand remora, the iMXrt1062 is not supported by mbedOS, so its probably a non-starter. the imxrt-1050 is supported, and there were a few threads on teensy forum about support for 4.0, but thats about it. you could probably use the remora.comp with your own custom non mbedos firmware, but you could do that with other spi comps also. But the main thing going on as I understand it, is that the remora firmware is based on mbedos framework
 

I got ya, I won't be doing any work on that myself, I don't know anything useful about programming. Good to know what the actual holdup is, I can keep my eye out for changes in the future.

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12 Dec 2021 22:51 - 12 Dec 2021 22:55 #228955 by Bari
@ cakeslob Do you know which STM32 device that these boards tend to use? I can't see the part numbers when I zoom in.

There have been discussions on IRC about a fork of Remora without Mbed in order to get more performance out of these devices if need be or to support chips not in Mbed.

Some of use are just waiting for hardware to be available after the current chip shortage ends.

It will likely sort itself out based on chip and board availability.

There are also three other recent LCNC projects that use a microcontroller or low cost FPGA for step generation:

www.forum.linuxcnc.org/18-computer/39037...-orange-pi-allwincnc

www.forum.linuxcnc.org/18-computer/42414...ethernet-using-esp32

www.forum.linuxcnc.org/27-driver-boards/44422-colorcnc

Lots more choices now.
Last edit: 12 Dec 2021 22:55 by Bari.

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14 Dec 2021 21:22 - 14 Dec 2021 21:34 #229076 by scotta
Hi Bari, interesting to hear about the IRC discussions. Remora (spiPRU) started as an Arduino project (on SAM mcu) and then migrated to Platform IO when I moved to the LPC1768.

Shortly after Platform IO stuffed up ARM support and hence the move to Mbed Studio IDE as the development environment.

Remora does not use an RTOS so any simple dev environment could be used as the base. Mbed Studio does give an easy to use environment with the build system being such that having hardware specific pieces of code being pulled in at compile time being really straight forward. Change the target and in comes the correct versions of code.

This made the addition of STM32F4 variants and now STM32F1 variants (in dev) quite straight forward.

I've been following the esp32 thread as well. Some of the Remora features would help there as well I think. The Remora step generator is a version of the standard LinuxCNC stepgen using DDS synthesis which solves a lot of the issues I see in that code. Along with the degrading step rates as more joints are added.

I'm curious as the perceived lack of performance?

Work on ethernet connectivity is ongoing and a great learning experience on my side. My first jump into ethernet. It's been a while since I last sniffed packets (RS485) when I developed the Huanyang VFD component. It matured and now is an integral component of LinuxCNC. Now sniffing UDP packets is keeping the grey cells active.
Last edit: 14 Dec 2021 21:34 by scotta.
The following user(s) said Thank You: AlessandroEmm

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14 Dec 2021 21:26 - 14 Dec 2021 21:29 #229077 by scotta
I'm very tempted to get one of these Ethernet Mach3 "cards". Apparently they have an STM32F2 inside. Level shifting with opto isolation would make for a more "industrial" solution. And the price is very reasonable ~$52 USD for a 3 axis version. 

Last edit: 14 Dec 2021 21:29 by scotta.

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14 Dec 2021 21:49 #229079 by AlessandroEmm
Apparently MX_master has looked already into these and found them not suitable. (forum.linuxcnc.org/38-general-linuxcnc-q...-card-with-linux-cnc) That said I found a thread with/of him on the russian cnc forum, he seems to be onto something new as far as my browser was able to translate. :-) I will look up the link again and post it here.

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15 Dec 2021 07:59 #229103 by Bari
I'm waiting for hardware to be available. I will try to find out why the step rates are not 2-3X higher than they currently are. The Novosun cards reach 200KHz step rates for each axis with stm32f2's.

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16 Dec 2021 21:07 #229203 by scotta

I'm waiting for hardware to be available. I will try to find out why the step rates are not 2-3X higher than they currently are. The Novosun cards reach 200KHz step rates for each axis with stm32f2's.

Step rate is determined by the base thread frequency, which is now configurable. It really comes down to how long the code spends in the base thread (doing steps) vs being out doing the servo thread an main loop. In the dev branch there is some thread debug code to allow some spare outputs to be used to show the thread activity.

Also, we could double the step rate by completing the step in one thread cycle vs the two that are currently used. I just have not seen the need yet for super high step rates on a real machine... But maybe I should for advertising purposes.

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16 Dec 2021 21:08 #229204 by scotta

Apparently MX_master has looked already into these and found them not suitable. (forum.linuxcnc.org/38-general-linuxcnc-q...-card-with-linux-cnc) That said I found a thread with/of him on the russian cnc forum, he seems to be onto something new as far as my browser was able to translate. :-) I will look up the link again and post it here.

Yes, that's were I noticed the card. I think his issue was wanting to use hardware step generation. For Remora, no issues with pin assignment with software step generation.

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