Connecting a 3A

Still very new to 3d printing, in fact still haven't bought one. A while ago I asked re. suitability of using 3A with Octoprint and got several answers principally the it was short on RAM and it only had 1 USB port.

Given the one USB port (which I assume goes to the printer)would it be true that the only way to connect Pi to PC is via Wifi? Or is it possible to connect a UART on the Pi (I assume it has one that is accessible) to the printer and use the USB to connect to the PC?

I would use the Pi exclusively to run OctoPrint so it does not seem optimal to use a £50 part when a £30 will do. Or have I completely misunderstood?

Yes that's possible (as long as the printers mainboard got a UART connector :wink: )

You could connect a usb to ethernet adapter to the pi and use it to connect it to your pc / home network.

Afaik there is no way to connect your pi just via usb to your pc. You would need at least something like this

Another way would be a usb-hub. With the help of the hub you are able to connect several usb devices to a 3A. I would highly recommend an active usb-hub (that's a hub with its own power supply)

Last thing -> I would go with a 3A+ - it shouldn't cost much more but you get a faster pi and 5GHz wifi.

There's something named "gadget mode" that will let you network directly over USB.

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If you're talking about having the 3A+ be connected to the printer board and to have a 3B, for example, run OctoPrint then I've already written this one up (using a virtual network serial connection). More The includes a table of performance information for the 3A+ (about 9% faster throughput than the Zero).

@OutsourceGuru. An interesting idea, but no that was not my intention. My problem with 3d printing is not that I need a 3d printer but rather I want a 3d printer. I live comfortably on my pension but nevertheless I don't have a lot of spare money, so I like to get value, thus the 3A+ instead of the 3B+.

Seems everywhere I look (RS, Farnell, Pi Hut) the 3A+ and the 3B+ is on back order, so the whole thing may be moot.

@PrintedWeez Now I'm really confused. Are we saying that the Pi is a USB Host, as apposed to a USB Device?

What would be the standard way of connecting printer to PI?

I've just realized that I'd completely forgotten that a Pi a an Ethernet port.

Just read this again and I'm pretty sure that I've failed to pose my question clearly, based on my forgetting that a Pi had an Ethernet port.

A raspberry pi 3a does not have an ethernet port.

Bugger, your're right but it does have Wifi, right?

Yeah it has wifi
The 3A got 2.4GHz
The 3A+ got 2.4 and 5GHz

Yeah that's the case for B and B+ models, @fieldOfView corrected me for the A, A+ and Zero models.
Those got no internal USB hub so the port is directly connected to the SoC which gives you the ability to run it in various device modes.

List of avaible modes:

  • Serial (g_serial)
  • Ethernet (g_ether)
  • Mass storage (g_mass_storage)
  • MIDI (g_midi)
  • Audio (g_audio)
  • Keyboard/Mouse (g_hid)
  • Mass storage and Serial (g_acm_ms)
  • Ethernet and Serial (g_cdc)
  • Multi (g_multi) - Allows you to configure 2 from Ethernet, Mass storage and Serial
    In addition to the above modules, a few other (less useful) modules are included.
  • Webcam (g_webcam)
  • Printer (g_printer)
  • Gadget tester (g_zero)

Via USB I would say :slight_smile:

Thank you very much for taking the time to provide so much information.

I am surprised to learn that the A model has some ability that the B does not although it's not immediately obvious how it helps in this particular case. What mode is the A's USB port in by default when running Octoprint?

The USB port is normally in host mode, so you can connect your printer (or another USB device) to it.
OctoPrint doesn't have much to do with how your USB port behaves though; that is all up to the (configuration of) the operating system (Raspbian, OctoPi, what have you).

While you may save money with the 3A, it's not a lot of money as such, but you would be causing yourself a lot of grief down the road.
Don't get me wrong - the 3A would probably do the job, but you'd be constantly on the back foot, trying to find solutions for issues that nobody else can help with because they don't have the same layout as you.
There may be things that happen on your system that don't happen on others because you run out of RAM, or because your system is just a fraction too slow and that hasn't been tested in development.
Whenever something like that happens, what tends to happen is people try help by trying out, on their system, some of the things that they think are causing you your problem. That works when you have ten thousand others with the same hardware, but it tends to die when only a few have similar hardware - just finding some of them online may become an issue.

The other problem is that as you grow into your hobby, you tend to want to do more and more complex things. You don't want your imagination curbed by your hardware. As your prints get longer, can you add a plugin to monitor the print from work? For the 3B+ there are thousands of people that can answer that immediately. For the 3A, how many could answer that? I know I couldn't

Best Regards,

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@FieldOfView thanks for the info.
@RichardP Thanks for responding in so much detail, I take you're point and will go either 3B+ or 4.

Does anybody have a which (3B+ or 4) is most commonly used? I assume the 3B+ would be the safer, more conservative option.

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Based on the usage stats it's 3B, 3B+, 4:

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i use a 3A+ running buster with octoprint to run my ANET A8

works fine, connect to printer via USB, and wifi for your laptop / pc

to set up connect keyboard / mouse to USB via hub and monitor to HDMI

install octoprint and connect to wifi (idealy set a static IP) and reboot

the monitor will show the IP to connect to, point your browser at the IP and ensure you get a logon / set up page, disonnect the USB hub and connect the printer to the USB port, then setup / configure octopi / octoprint as normal