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How to best design a circuit board?

So I have a motorolla Z3 Play, and honestlythis is one of the best devices I’ve ever owned. Not phone, not android device, but device in total. Its built via classic lenovo professionalism, doesn’t cause complaints spec wise so it won’t lag, and feels the standard aremis A++ rating.

But it doesn’t have a headphone jack, my vape’s battery is about 3x bigger than this phone’s battery, and I can’t map the volume buttons to be music player controls, something that I haven’t seen since my first smart phone, an LG Optimus G.

And trust me, I have music going almost 24/7 365 as much as possible, so those remappable buttons are a must for me. Remappable buttons in general, actually.

So what I want to do is make a moto mod. This moto mod will provide a slot or two for 1 or 2 18650 batteries up to 3000 mAh each, a set of 4, 8, or 10 remappable keys (I used a small external bluetooth set of keys before that just paired with my phone and a tiny app I made). Probably 4 or 8 tho, I think I’m the only one who’d need ten lol.

Then the peice de resistence.

A quad channel DAC that has a 3.5 jack and a 1/4" jack.

My pioneer DJ XJ-H7’s are supposed to be used on 1/4" but I took the adapter off. But it’d sure be nice to use them fully! The DAC in both my OG and V20 make these headphones rock, and I’m convinced all phones need hifi DAC’s built in.

I have a half assed mockup of how this all goes together in my head and sorta drawn out, but I’d like to properly design it to be printed and tested sometime this year. Is there an app or site that could help with that ol am I on my own?


This sounds like a pretty big project for the experience level.

If you’re starting from zero then I’d suggest learning:

  • At least basic understanding of electronics (e.g. Ohms Law)
  • What various passive components do
  • Familiarize yourself with datasheets
  • Probably KiCAD

And for the actual design I’d break it up into pieces. Design and test each part of the mod separately before sticking them together, that way troubleshooting will be much easier.

As for the physical PCBs, I’ve had good luck with OSH Park. They have a minimum order quantity, but it’s reasonable and the prices are fair IMO. All of the PCBs in my “Break a Leg without the challenge” thread are from OSH Park.


I have literally zero experience with this but I wish you the best of luck on this.

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I have a Moto X4 and it has this function on Android Pie in the Moto app.

If you want a decent portable DAC there’s this one that’s cheap, doesen’t take a lot of space, has firmware for 24bit/192KHz, flat audio response and can drive decent headphones. I’m trying to buy one but it’s out of stock on Amazon where I live.

If you want to add buttons you could buy this thing and call it a day.

Now onto a more direct answer about your idea of making a Moto Mod. To do that you need a Motorola developement kit they give out to companies to make mods. It’s required because Motorola requires a deep integration with their phones to work properly. The developement kit comes with software APIs and some kind of hardware (I don’t precisely know what hardware).
Regarding circuit design you’re on your own I think. There aren’t any sites that I know of that would check what you designed. The only way to test before making prototypes is using softwares like Matlab to check if all the parameters in the circuit make sense. It also gives you the possibility to have a dynamic circuit going on.
Have you been able to source out the DAC chip? You’ll also need an amp to drive your headphones, which requires another circuit.
In the end, considering everything you want to put in that thing you’re going to end up with a 4-5 layers PCB to keep everything well isolated.

To be honest, as exciting as sounds making things on your own, I don’t think it’s worth the time investment when you can buy some cheap things off of the internet and solve your problems.

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This is a big fish.
What you have is three different devices in one: battery controller, I/O device and DAC.

Draw it out on paper.
3.5 and 6.3mm jacks and 18650s are known sizes. Then you have the minimum size the thing will be.
Programms like Fritzing (simple) or KiCAD (advanced) are of no use when you have no idea what components you need.
So I would recommend you go searching for components (charge/battery controllers, DACs, microcontrollers, etc.) and look in their datasheets for “default setups”.

Tip: Don´t start the first version with SMD components, they are a royal pain in the ass to solder by hand.

Two layers are enough for battery controllers and DACs/Amps. No idea how you got to >2

Very small single cell LiPo charger:
And a bigger one:

Amplifier chip I used once (not sure if application is right):
Two channel DAC that does not suck:


Fair enough, but he wants to have buttons too and I thought about having DAC and AMP on two different layers. So that makes at least three I gueeess. Or I might just be dumb, one of the two things.

To design a PCB, you’ll want to use something like KCAD or Eagle. This is not a simple task.

Designing arduino breakout boards is difficult, but when you start mapping out traces for small components like you are describing it will be very expensive and time consuming.


This project is tough but you can do it. You will have to read a lot. Divide your project into parts to be simpler, and do “test boards” for each part to test if things do work. Only after you tested everything go to kicad and make the pcb design and test it again after you make it. If you need some help just share what’s your problem if I am online I might be able to help.

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I always deactivate any factory software, so honestly I wouldn’t even look in there. In 4.2-.4 it was just an in-system option, and still is, but no one lists it for some reason. Its annoying TBH.

Thank you for your input tho.

The Moto software is the only one I can tolerate, that’s why I keep buying their phones. You’re welcome!
My Moto app is at version 8.0.23, but I don’t know if it differs much between different phones.
Anyway good luck with your project! Hope to see it come to life, no matter how hard it is.

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Could try easyEDA (that’s what I’ve been using anyway). It won’t make corrections for you, but it’s about as accessible as it gets.

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I can recommend Proteus, it is decent at the routing part, it has a lot of components bundled and you can run simulations. Used it myself when i made some controller boards for around the house with close to no prior knowledge of electronics beforehand.

Took me around two weeks from start to finish to make a hydroponics controller for the greenhouse, including a mod for my 3D printer so I could route my own PCBs.

I wasn’t able to find it for any other OS than Windows at the time, but it does work in a VirtualBox VM installation of Win10.

Can also recommend Autodesk Eagle, friend of mine who’s an Electrical Engineer uses this one.