Tobius Daichi
Hello!
3+Pi is nothing conceptually new. This is just as any 3D printer based board which talks through UART. Except instead of having a USB to UART layer, this is directly working UART to the Raspberry pi.
Designed specifically to act as a Raspberry Pi Hat. 3+Pi conceptially means, 3 Axis or more (thus the +) and along mounted onto the Pi.... (umm... Thus the +Pi again.)
With a ARM Cortex M4 STM32F302CBT6, the 3+Pi will be able to handle all the low level logic and Realtime aspect of driving the motors for whatever purpose you might want to throw at it... Hopefully. Using the TMC2041s dual in one package stepper drivers communicating with the STM through SPI, the option to add 6 Degrees of freedom will not be an issue... Unless maybe when you're driving the stepper coils hard then yeaaaahhhh probably not?
Optional CAN controller will let you use the 3+Pi for any CAN-able (hehehe) devices in the bus allowing you to directly talk to the STM for stepper feedback and monitoring or stepper driving. With the optional feature to talk to the Pi and ask it nice questions like how is the temperature going and how much resources are you drawing. How are you feeling? It's good to talk...
Finally, with the whole doctrine of USB-C motivation, I have succumbed and made the board support USB-C 100W full usage. I mean it will be able to negotiate a whopping 20V 5A if the supply grants it but will be able to programmed to drop the power draw should there be an issue. If there isn't any 20v or high current supply, the board will work functionally with normal 5V 3A powering only the Pi and prompting the user about low power input thus putting the STM32 to deep sleep until next power up hoping that the power supply is enough to juice it up.
So where can this be used? Possibly for 3D Printers, CNC machines, Laser cutters or virtually any low power demanding 6DoF applications. I have so many outlandish plans for this project such as adding the potential to respond to physical motion feedback on said 6DoF to have a good closed loop control system. I hope this is inspires you to design your own crazy project (please feel free to let me know about it and I'll definitely try to support you with my skills as much as I possibly can) and or feel like oyu want to help out. Because sure enough, you are happy to join this project! :) Thanks for reading...
/..\
Here is the previous extract I had for the board originally. I believe in archive and less deletion as it's an important philosophy to show other people and individuals the improvements/non-improvements they make.
{The board consists of the Cortex M4 STM32F401RE chip handling mostly the grunt of the lower level tasks needed to create the signals need for the 4x TMC2100 Stepper driver modules. A bunch of bulk Al caps to smooth out the power supplied and to be rated to handle 24V input. This reduces the need to having thicker current power supplies rated at 12V. [Edit: 18-02-2019 This was the original idea with Prototype V1.0-1.2p]
My power target is to go lower than 96W total....For now. [Edit: 18-02-2019 This was the original idea with Prototype V1.0-1.2p] }
This is rather a rapid prototype for now, so it's been designed rather quickly and will possibly have some bugs/hiccups here and there. I have been working on this after my usual day time work during the weekdays so ... I'd say there isn't much time put into this yet but regardless, I intend to do it no matter how long it takes because of I love doing such projects.
Teemu Hakala
Erland Lewin
tobychui
@Tobius Daichi Cool project! I have been looking for an available commercial replacement controller board for Creality 3D-printers that either fully integrate with a Raspberry Pi for OctoPrint or a replacement controller board that can also fully replace a Raspberry Pi to run OctoPrint on its own. I have a couple of tips from my reading up on replacement 3D-printer controller boards (so as a disclaimer please note that these tips are not from my own personal experience so I cannot take any credit).
First tip, you should know that TMC recently announced their new TMC2209 which are relatively inexpensive stepper drivers that are specifically targeted and optimized for FDM/FFF 3D-printers. Quoting and pharaprasing @warlockd here; Compared to the older TMC2208, TMC2209 apparently is supposed to supports “multiple chips being on the same UART bus so no more having to use software uart or a mux, you use the MS1/2 pins to choose what the address of the chip is and you can send read to individual chips. Only 4 addresses though so not sure what to do about E1 but I guess its ok for it to be sharing the E0. Sensorless homing works so much better with interrupts, especially with Marlin's software design. Seems TMC went all out with the 2209, better stealthchop switchover. 2amp rms.“
Second tip, will you be using/recommending a using a 2oz copper thickness for all the layers of the board? I read on Reddit that Griffin_459 (Paquette Engineering) who designed the newly announced TH3D EZBoard Lite (formerly "TH3D Tough Controller") used 2oz copper thickness on all 4 layers of their board instead of only 1oz copper thickness to specifically deal with the heat dissipation of TMC2208 and TMC2209 stepper drivers, that way they do not even need to use heatsinks at all as the whole board act as a heatsink. See his comments https://www.reddit.com/r/3Dprinting/comments/bro0pn/brand_new_tmc2209_stepper_drivers_coming_out_soon/
Third and last tip, as an alternatively to making this board as a "hat" for Raspberry Pi you could at least in theory replace the STM32F3 MCU with an MPU from the new STM32MP1 series which has an very fast integrated MCU for a totally integrated solution as that series combines one or two Cortex-A7 processors alongside a Cortex-M4 MCU. https://blog.st.com/stm32mp1-mpu-stm32mp157a-ev1-stm32mp157c-dk2/ STMicroelectronics claims STM32MP1 architecture enables developers to use the same software as STM32 MCU series, and theoretically, with the STM32MP1 MPU series having both a Cortex-A7 CPU and a Cortex-M4 MCU you could run both OctoPi with OctoPrint or similar Linux distribution as well as either Marlin or Klipper 3D-printer firmware on the same board, without the need for a Raspberry Pi at all. Should be noted though that even the fastest Dual Cortex-A model of STM32MP1 only run at 650MHz per core and supports up to 1GB of external RAM so that part is on paper maybe only twice as powerful as a Raspberry Pi Zero when considering STM32MP1 are based on Cortex-A7 instead of the older ARMv6., but that should still be enough to run OctoPrint smoothly https://www.cnx-software.com/2019/02/21/stmicro-stm32mp1-cortex-a7-m4-mpu/ The available STM32MP157C-DK1 and STM32MP157C-DK2 $99 discovery kit are relatively cheap at $69 and $99.