Reading the detailed architecture description for the ARM CPU used in the ~$35 Raspberry Pi 3. Trying very hard to suppress a tendency to giggle.
Seriously? There is this much design in a cheap CPU?
For reference, I lost interest in CPU design after the Intel 486. My judgement then was that multiple CPUs would be more efficient, and mainstream PC CPUs were then dominated by the needs of gamers, driven by the needs of single-threaded games.
In the present, Intel based their massively multi-threaded Phi around a core essentially one generation past the 486 … and ~25+ years later. I will stick with my old judgement.
The amount of architectural nice bits in a quad CPU on a current ~$35 board is completely and ridiculously absurd. Fairly sure a Raspberry Pi 3, running Linux, could drive a next-generation 3D printer. The lack is the appropriate “shield” (with stepper-drivers) and the software to control.
I am not going to test the assertion, in my present iteration. Ordered hardware to match the software (g2core) I want to run, with least present trouble.
The Arduino Due is here. The RADDS board in on the way from Denmark. The Trinamic mini-boards are on their way from Germany. Cloned the g2core repo so I can build to match the hardware.
A number of people have 3D printers based on older raspberry pi models and yet for some reason people still deny that it can be done. Personally, I think mini driver boards for printers might make things more convenient. You could then use a board for movement control, a board for extruder control and a board for effector connected gear on a delta printer. (Shrugs) Less wires. The mini controller boards would be driven vi i2c or spi on the gpio pins of the pi. Different cores could be used if context switching costs can be kept under control. A second (cheaper) pi could be used to act as an interface if needed.
Direct firing, not likely… probably with h-bridge. The devil is in the details so they say… probably because not mentioning details creates confusion, and mentioning too many details creates confusion.
There seems to be a lack of step by step directions to make something like a RAMPS board for pi. If you figure out how to do it, almost anything can be done (if no consideration for cost is an issue). By the way, if anyone knows a simple fix to add extra I/O pins to Arduino Mega and Pi Zero, it would greatly help with a project of mine.
That CPU was developed for low-mid range smartphones, and also as a low-power complement to the more powerful CPU in a high-end phone. It’s only in the RP3 because it also happens to be a good fit. It’s not a good for for real-time control because it’s designed for a different purpose. The ‘shield’ and stepper drivers etc. are where the cost increment comes in with control boards, not the CPU. (as well as the software and development costs)
@Sven_Eric_Nielsen all 3D printers that I know of have a stepper driver. That stepper driver may be separate from the board or included. I was just saying the pi was the brain with no arduino included. Running a stepper directly off of pi gpio pins would result in too little amps or volts, damage to the pi from current backflow and running out of gpio pins.
@NathanielStenzel
Well this is exactly how I understand what you said. Therefore I’ve asked for printers which are using a pi. I mean for controlling the stepper motor, reading the switches, controlling the hotend end heated bed and so on.
I know there is the beagle bone. But this is not what you’ve mentioned. You said “older raspberry pi’s”
@Sven_Eric_Nielsen you do not even want to use a stepstick? The amps and volts for running an arduino/pi are not sufficient for any decent sized stepper motor so I am confused by your insistance of having no stepstick or other driver module like the A4988. Even if you could get the power within spec for the steppers, the hotend will require 12V or be useless. You do not run 40W (standard heater cartridge) through a pi or arduino. You would use a mosfet to control it.
@NathanielStenzel
Do you even read what I write?
Controlling the stepper doesn’t mean driving the stepper. It means controlling.
And this means sending signals to a driver. Which is obviously a stepper driver.
As I said, I understand what you wrote.
So to write it a bit more precise/simple for you :
Which printer is running without a separate i.e. Arduino and controlling the stepper drivers, mosfets and (what ever else is needed for a 3d printer) directly?
Or in other words(because we’re talking about a board which usually runs linux):
Maybe you can give us a few examples of printer that is directly driven by a Linux computer?
Hmmm…you do realize that most control boards have a stepper driver module built into the board, right? You can easily make them yourself for cheaper than what they sell for. Peter of LaserWeb and OpenBuilds even has the designs for a board to strap onto a raspberry pi zero for cnc milling that he made…I think from scratch. That dude kinda rocks…even if his designs for circuits kind of require outsourcing the blank board fabrication due to multiple layers. That is only the tiniest of issues that I have with his circuit design work.
@Brook_Drumm Yes … the printers you mention use the Printrboard G2, or something else? BTW, there are a few folk (including me) who wish your Printrboard G2 was 24V (for the steppers). Guessing your bots are all 12V, so not a priority for you.
@NathanielStenzel If you can find some examples, that would be great. I heard from others that the Pi has not worked well as a printer controller. Maybe that is true, but I suspect it to be very possible to control a printer with the right shield/hat and drivers. But I am not trying that exercise in this iteration.
At the very least, it is not a well-described path.
@Sean_Houlihane There was a point in time, not so very long ago, when you could theoretically go to jail for life, if you exported a computer from the United States with less compute than a low-end cell phone. (Look up ITARS, if you want. Got a surprise visit from some nice NSA folk when I wanted to use encryption, early.)
That low-end quad 1.2Ghz ARM CPU is a lot of compute.
@NathanielStenzel
Ok, obviously you don’t want to understand me.
I don’t care about how the stepper is fixed and I know how these boards are made and how to design them. This is not the point.
YOU wrote that a number of people have 3D printers (not cnc mills or what ever) based on OLDER raspberry pi’s. I said basically : SHOW ME!
But instead you’re just talking about strange things.
Again, actually I don’t care about how the rest of the peripherals is designed. I want to see these printers YOU’VE talked about! Printers based on older pi’s.
@NathanielStenzel
I did this research several times. And I’ve only found one in the last 3 years. And this was even just a case study. And the results were far away from reasonable. Therefore I’m asking for this big amount of people you’ve talked about. Obviously I’ve missed something.
And by the way, you don’t do the research for me. I’m in doubt that your statement is true. And you have to prove that it’s right if you want to keep some kind of reputation. Making such statements without being able to show facts is usually not the best idea.
