Remora - Rpi Software Stepping Using External Microcontroller via SPI

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17 Jul 2021 11:21 #215129 by mhel
@Bari, I believed that's a bootloader for the pi.

@Scott, if  for 407 like the BTT SKR 2 this could be a start
SD Card Boot Loader

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17 Jul 2021 21:38 #215176 by scotta
These 3D printer controller boards come with a bootloader already flashed. It's a case of knowing the start address that the bootloader will lump to and then have the linker set up accordingly.

Spent an hour or so yesterday looking at the Marlin build system. If the board is supported by Marlin we can take the offset values from their ldscript.ld and platformIO ini files.

A really need to get a board to start playing with.

Rommel, your work to get the SPI DMA slave working was my biggest concern, thanks for this.

BR
Scott

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17 Jul 2021 22:47 #215185 by Bari
Lots of these micros also have Ethernet. I am wondering now about combining this other project into this one forum.linuxcnc.org/18-computer/42414-lin...ethernet-using-esp32

They started with ESP32 which can be another platform to support over SPI as well as Ethernet.

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18 Jul 2021 00:37 #215192 by mhel

These 3D printer controller boards come with a bootloader already flashed. It's a case of knowing the start address that the bootloader will lump to and then have the linker set up accordingly.

 

Ah ok. funny, I have cloned so many 3d printing related repos, but I've not looked at the hardwares.
Tomorrow I'll hookup  my contraption to my unfinished router without a spindle but atleast I'll have all 3 axis moving.
I'm just hoping Rpi4 3.3v is good enough to drive my TB6600 through an LPT cable.

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18 Jul 2021 20:44 - 18 Jul 2021 20:45 #215251 by mhel
What's the possibility of having a 'stepconf' for Remora?The ini file seems like an art-form when it comes to acceleration/velocitysettings. My setup is badly tuned, couple that with bad specs on my self-built machine. But I do have motion on all axis and very responsive.I was hoping I coud post a vid of it plotting, but Inkscape generated gcode has huge values in inches, the only thing changed when switching unit was the G20/G21 the rest of the code still uses values in the hundreds of unit.This is the beginning of my stand alone controller :-)
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Last edit: 18 Jul 2021 20:45 by mhel.

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18 Jul 2021 20:51 #215252 by Bari
A well written howto for noobs would be much better than a Steconf. Stepconf does not do any tuning. It is just a way to get a basic config working. Tuning is always done using an editor on the INI and HAL files.

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18 Jul 2021 21:08 #215257 by tommylight
Inkscape normally works in pixels, that has to be set in mm or inches in the drop down menu top center, right after the dimension values.

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20 Jul 2021 04:33 - 20 Jul 2021 04:40 #215368 by Doogie
@Aaroncnc, the way I tested was pretty crude in that I just went with longer wires and made stuff or ran fake runs with nothing in the extruder until I got SPI errors then figured the workable length was between the shorter and the longer which still failed but after a bunch of testing.

My hand wired 2x5 connector adapters failed after a time at 70cm long ribbon cable and worked really well 20cm. My pcb based 2x5 connector adapters have been working so far with only 1 SPI error over a few hours of testing on the 70cm ribbon cable.

70cm is very long and should be way more than anyone would normally need.
Last edit: 20 Jul 2021 04:40 by Doogie.

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20 Jul 2021 18:50 - 22 Jul 2021 04:20 #215432 by Doogie
To do some validation of the PCB based SPI connector adapter boards I have a long 700mm GLCD ribbon cable between the rPi4 and SKR1.4t adapters. The GCode file is one doing a ~100mm diameter spiral having 50 rotations at 200mm/s and I have that in a loop running 50 times and each loop raises Z by 2mm.

I've run it 8 times now without any SPI errors. I see on the DRO the Vel is pegged at 9000 most of the time.

I've attached the arcBlendTest file below.
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Last edit: 22 Jul 2021 04:20 by Doogie.

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21 Jul 2021 13:11 #215493 by mhel
I hit a few snags.
1. My neighbour doesn't understand my obsession with this ;-)
2. I think I killed my X axis driver.

I finally made a crappy vid  Aircut  ( streamable.com/5yszzq )
Warning it's headache inducing, bandwidth consuming.
I think it's not bad for a bent X axis leadscrew with a .5" pitch, atleast I think I have the scale correct.
In any case it's just a proof that the controller works,  pretty stable too.

Oh and this jscut.org/ is a good start for a newbie it imports svg from inkscape .

@Scott  I bump the PRU_BASEFREQ to 200kHz just to see what happens, the video is the result.
But after re-run for a couple of times the x axis driver is dead.  I just realized that there's no configurable option to
change the step pulse width. The TB6600 I'm using apparently has a minimum pulse of 5 uSec probably more.

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