Basic Information:
Printer Model: DIY
MCU / Printerboard: DIY STM32F407VET based
Host / SBC: RPI 4b
klippy.log
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Describe your issue:
Hello
Sorry first time posting here but I googled a lot and didn’t find any info on this. So I’m making a custom DIY board, STM32F407VET board with 9x TMC2209 and I would like to know which pins are OK for STEP signals? I’m thinking it needs to be wired to a Timer? What are the limitations?
Also can someone explain to me the UART wiring of the TMC2209. I know the pins are bit-banged so any pin should be ok, but every schematic I see uses two pins of the mcu via a resistor. Is this still needed or can I just put a pull-up resistor?
Thank you
Maybe @mykepredko can help.
Without any offense meant, this kind of question might indicate that you would have a higher success rate with less financial exposure by using an existing board.
Of course, it depends on whether you are just looking for a learning experience or actually need the board.
No offense taken. This is more of a hobby for me than just buying a board.
But it seems I can’t find any info on pin requrements.
Hi @TadyTheFish
The STEP pins do not have to be wired to a timer output - their signals are produced by Klipper (or Marlin or whatever) in coordination with other actions so setting up a timer to send a predetermined set of pulses is not required.
As for the UART pin, you only need one on the MCU. I recommend putting a 10k pull down to keep the TMC2209 in power down mode until it is required. This information is available in the TMC2209 datasheet - why aren’t you looking there?
I agree with @Sineos in questioning your decision to make your own board, going straight to a nine driver board without a clear understanding how the selected driver chip works has a lot of risk. Along with requiring experience in putting down high speed MCUs and providing communications, you need to have a good plan for power distribution, heat dissipation and how you are going to lay down your traces. Chances are, you’re going to need a six layer board.
Personally, I would recommend starting with something like an Octopus or a Manta M8P (which have eight built in drivers) and adding a CAN toolhead driver, like the EBB42, for the final driver. Much less costly with a much higher probability of success and still provide you with a lot of opportunities for learning how a 3D printer controller board works.
Thank you for the information.
As for building my own board I know the chalanges and alot of pit falls.
4 yeas ago I already made a board that handles 7 steppers ant it works great. But I recently changed some hardware on the printer and added functions so I figured ehay not make another board. I’m building this one from scratch because the first one I made in Eagle and I moved to KiCAD since and porting it is not worth it.
On my previous board I was sticking to the pins for stepper stepping from another schematic so I figured now why not ask if this is needed or not. I didn’t really know if klipper uses hardware to generate pulses or is it all handled in software. And for UART i also copied the wiring (RX and TX via resistor) but now I war setkinking why is this needed if only one pin is defined in the config file.
As for board making I have quite alot experience with PCBs. I’m not a pro by far but I like doing sone projects for fun.
For example building this printer was more fun for me than using it. I’m an electronics guy so for me it makes sense. Also I have been using STMs for a long time.
I even made a EtherCAT slave from scratch so I know the deal with ground planes, decoipling capacitors, reset curcuits, impedance matched traces,…
your info hase been a great help thank you again