Sooooo I decided to use the SKR Mini E3 V3 for my LR3 build: BIGTREETECH SKR MINI E3 V3.0 32 Bit Control Board for Ender 3/Ender 3 | Biqu Equipment
I got it because it has TMC2209 drivers, is pretty well-adopted by the broader Marlin/3D printer community and is cheap (~$45 for just the board on Amazon or $85 for the board + TFT35-E3 display). And because I have an Ender 3 so worst-comes-to-worst I can just swap it in there as an upgrade for the printer.
Yup, I know it’s only 4 drivers instead of 5 — Z driver multiplexes 2 Z ports which as near as I can tell are parallel. I wired all my axes in parallel for simplicity (ie stepper wires are 1:1 w/ axis ports).
I’m using sensorless homing which is super simple to set up - just have to put jumpers on 3 pins and make a few Marlin tweaks.
I read all the info I could find on these forums re: why >=5 drivers + series wiring is better; some salient threads:
- Parallel vs series on your steppers - #52 by unltdsoul
- Instructable about running your stepper motors in series, not parallel.
- Can someone explain dual endstops and autosquaring to a dummy?
- Biqu is stopping SKR Pro production soon - #35 by jdwolk
And I think I’m comfortable with the tradeoffs as I understand them. Namely:
- Less power from parallel wiring, particularly Z axis because of the driver multiplexing (I haven’t noticed problems yet…maybe I will later?)
- No dual endstops (I’m fine w/ physical endstops + sensorless homing)
- No auto squaring (because no dual endstops - I’m comfortable w/ getting things as close as I can by hand + calibrating, offsetting, and storing offsets in eeprom)
- No auto leveling (I’m not 3d printing so I don’t care)
I’d be interested to know if there are more tradeoffs I’m not thinking of and/or if my understanding of ^ is incorrect.
So - for people who are fine making the same tradeoffs as I did for their LR3 builds + want Marlin configs to Just Get Things Working w/ the SKR Mini E3 V3, here are the tweaks I made: Marlin SKR Mini E3 V3 Configs for V1Engineering Lowrider 3 · GitHub
Worth noting: I used GitHub - bigtreetech/Marlin at SKR-mini-E3-V3.0-G0B1 as a base since it’s already set up for the SKR Mini E3 V3. This is different than the original Marlin source and/or what the V1 MarlinBuilder (GitHub - V1EngineeringInc/MarlinBuilder: MarlinBuilder) uses for a baseline. I picked through the MarlinBuilder source for quite a few configs and selectively brought in what I thought I needed.
I just build in the root dir using
platformio run -e STM32G0B1RE_btt from the CLI. Then I copy the built binary in
./.pio/build/STM32G0B1RE_btt/firmware.bin to the SD card of the SKR Mini E3 V3. Probably have to do something different if you’re using PlatformIO from VS Code, not sure.
Hopefully this is useful to someone / saves a few hours for ppl like me who choose the SKR Mini E3 V3