Help with scratch built Arduboy (no modules)

Hello, just signed up! new arduboy on its way (I just recently got the maker bug, and I might recognize some familiar names here from the pokitto community).
Aside from willing to play the amazing games made for the arduboy, I’m also itching to try building my very first pcb, could someone help me out?
Disclaimer, I have no pcb design skills, this might take a while and a lot of questions.

My goal is to make a dual layer pcb arduboy compatible handheld with the following specs:

  • uses AA batteries, no idea how many will be needed?
  • same arduboy components: chip, display, etc.
  • has flash storage capability
  • minimize use of micro components and favor big resistors, diodes or whatever else is needed. Unfortunately I will still have to deal with the tiny processor, which seems pretty annoying to solder by hand.
  • micro-usb or usb-c, whatever requires less hustle

I guess my first two questions are:

  1. what’s the exact parts list?
  2. where can I find the arduboy circuit schematic to make my own pcb?

P.s. yes, I know it’s a long road to learn all this stuff. No, I don’t want to start by getting a bunch of ready-made components.

Sorry for the long post! hope someone can get me the ropes to start : )

Hey there! Nice to see you here! Here’s a link for the schematics

Have fun!

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I retitled this and moved it over into the help and information section since it sounds like you will need a lot of it before you can start building. My suggestion is to start the thread in the home made section once you have some of these concepts figured out and have started assembling the parts.

You can do it, it’s not that hard, just takes a lot of patience!

thank you @Vampirics ! I can’t wait to play some of your games on the arduboy!

And thanks for the encouragement @bateske , it will take some patience and will to learn indeed.

First step is learning how to read that schematic 8 )

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I’d recommend 3 for simplicity. giving 4.5V for regular batteries and 3.6V for rechargables. Using AAA size batteries will be fine too unless you plan on using a big 2.42" display

The core parts that make Arduboy are an Atmega32U4 and SSD1306 OLED display.
You probably want to get a Atmega32U4-AU as that model comes in a slightly bigger package (TQFP).

SMD parts come in different sizes. If you don’t want to use through hole parts then 1206 SMD parts can still be soldered well by hand.

don’t forget the Micro USB connector and OLED display cable.

Well they’re good for getting to know the parts and for prototyping.

for your PCB design I recommend to check out some of Adafruit and Sparkfun products. Most of them have their PCB designs avaIlable for download.

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If you’re going to run at 4.5V and use a “raw” display with just the chip in the flex cable (i.e. not a module with a circuit board), that voltage is well over the specified 4.0V absolute maximum. In this case, I’d suggest using a 3.3V regulator for the entire system. Regulating to 3.3V would also benefit a flash chip.

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Thank you for the advice guys, from what I’ve seen today getting lost in KiKad, the battery aspect will be something I’ll be able to understand once I have a better understanding of the whole thing.
I didn’t even know the flash memory would impact on consumption!

Today I started watching some KiKad videos, it’s starting to make sense, although when I look at the arduboy schematic some symbols are still a mystery, like the P$1 and such.

The schematic hasn’t been fully cleaned up. The 3 diodes with the P$x text is the RGB LED.

here a edited version with some minor changes and labels added that might help clear some things up

Edit: updated image

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For completeness, you may wish to label LED3 (in the Charge Controller area) as “red”.

Well noticed :+1: Missed that one!

Edit: Fixed

thank you! this is all starting to make some sort of sense, adding the atmega32u4 to kicad as a first step : )

My steps will be as follow, please let me know if this is the way to go:

  • design schematic in kicad
  • generate and order component list
  • test it all out on a perf or bread board (btw, how do I turn the cpu into something I can stick on a perf or bread board?)
  • pcb design time!

One thing I did not mention yet, is the reason I’m going all custom with this.
I don’t actually intend on recreating a direct clone of the arduboy, instead I want to mash the arduboy with a Pocket Operator by having the same arduboy components with a totally different button layout made of a matrix + a potentiometer.

Along the way I will decide on the details, such as buttons and screen.
One idea could be to have actual mechanical keyboard switches, in which case a bigger screen like the one used on the ardubigboy might make sense, or the gorgeous liquid crystal display I saw posted here as well.
Dunno, all too exciting and I’m miles away from actually having anything working :slight_smile:

You could use something like this (I searched eBay for “tqfp44 adapter”)

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Hello, I kinda got stuck now that I need to face the batteries issue.
I’m learning about voltage boost regulators, apparently I can get stable 3.3V out of two AA batteries, which would be my idea goal, but is 3.3v enough?

Apparently this regulator might do, but that’s a lot of components, will I really need all of that? even the inductor (which I barely know what it is)?
image

Maybe something like these charge pumps instead?

“The MCP1256, MCP1257, MCP1258 and MCP1259
are inductorless, positive regulated charge pump
DC/DC converters. The devices generate a regulated
3.3V output voltage from a 1.8V to 3.6V input. The
devices are specifically designed for applications
operating from 2-cell alkaline, Ni-Cd, or Ni-MH
batteries or by one primary lithium MnO2 (or similar)
coin cell battery.”

Only outputs 100mA though, so may not be enough - are you planning on including all the LEDs?

3.3V is enough.

Actually it’s not. If you want less parts you should use more batteries so you don’t need to boost the voltage. (that’s why I sugested 3 earlier)

Think of it as a transformer.

Note if your going for the big 2.4" OLED display you’ll need a DC-DC converter for the for the OLED panel. It requires a higher voltage (somewhere 12-14V iirc) lower is possible at the cost of less brightness.

You could leave out the DC-DC converter for that too if you add even more bateries :slight_smile:
If you’re going to add mechanical keys and the 2.4" display it will get relatively large and adding more batteries shouldn’t be a problem. It would become heavier ofcourse but it would also last longer.

So many design choices…

You reckon with 3 or 4 batteries I might not need any sort of current stabilization and go straight to the atmega?

You’re not keeping notes. I’ve already suggested in this topic that you regulate to 3.3V.

Depending on your current draw, a simple linear regulator should suffice, such as an LM1117, AP2114 or similar.

Oh no! I keep coming back to your posts, I just didn’t know there were linear regulators as well as boost regulators.
I’ll look into that, thanks!

It’s better to regulate, but with 3 or more batteries you should be fine to boot and run for a while. But you will only get maybe 50% of the battery life you would with a charge pump, because the batteries will still produce a ton of current below the voltage cutoff of the mcu.

That said, with primary cell AA or AAA batteries you are probably talking about dozens of hours of playtime anyways so it may not matter that much.

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