PCB design based off UNO

Hey, I am reasonably new to pcb design (new in that I have gotten a board made but I have lots of designs that I’m not sure about). I recently made a simple board, a Atmega8 as a USB controller and the Atmega328 as my main controller, to later turn this into a controller for my model rockets and other projects like that. It is heavily based off the Uno schematic however I was wondering if someone could give it a check over to make sure you think it would work, given a 9v supply voltage.

If you don’t have time to check or I have done a terrible job, could you point me in the direction of someone who has made a board like this or somewhere I could learn how to make boards like this.

Any feedback is appreciated, thanks.

The design is too complex for someone to casually check it. And I'll guess it was mostly copied from an online schematic so any errors would likely be transcription errors.

This board is ambitious for a hobbyist. Having the design correct is only 10 to 20% of the job. The real challenge is how you place the components on the PCB and how you run the traces etc. This is not something one can answer in a forum post. You should google the subject and learn from what others have done.

As an aside , what will provide your 9v supply ? A small 9v smoke alarm type battery will probably not be up to it .

No one can do a thing with screen dumps, they are completely useless for doing what you ask. The best format is a PDF file.

I would have the design much simpler.

I would not include a USB to serial adapter. Just a header to connect an external serial adapter is OK.

The net result then is that if you choose the regulator wisely, you have an Arduino board that can have a sleep current in the 2uA range.

So you can get more for less.

Hi, I have am reasonable new to designing pcb’s, in that I have plenty of designs but haven’t gotten any of them made or tested. I recently made a simple schematic consisting of an Atmega8 as a USB controller and an atmega328 as the main mc - it is heavily based off of the Arduino uno. I am planning on using this to control rocket gimbals and future projects like that.

I was hoping someone could take a look and either give me some advice or tell me where I went wrong. IF you don’t have the time to check it, any recommendations to where people have done similar or materials I could use to learn from would be appreciated.

Any feedback will be appreciated, Thanks.

The 1st schematic isn’t readable. Use “export image” at at least 150dpi, rather than a screen shot.

Why mega8 for usb? I hear that the sw usb implementations are failing with newer PCs.
I like pre-made Ch340e modules when I don’t want to mess with fine pitch smt! https://www.ebay.com/itm/5PCS-CH340E-USB-to-TTL-Serial-Converter-Replace-Module-for-pro-mini/1534829780543D555018%1

Any feedback is appreciated, thanks.

Only post images where the printing is legible?

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Thanks in advance for your cooperation.

As others have said, such a complicated design is a jump into the deep end. How are you even going to assemble that at home? Have you ever worked with QFN parts like the 8u2? They are not pleasant to work with, let me tell you that; I have a lot of experience assembling boards at home (heh...) but I can't do QFN's reliably.

Secondly, the Uno is a foolish base to use for such a design, it is bulky, power hungry, and makes numerous dubious design decisions. Use a pro mini as your base - and then go look at the price of pro mini clones, and explain to us all why it makes sense to design your own when you can't get the atmega328p alone for the price of an assembled board from china.

Using a 9v smoke alarm battery is a terrible plan; those are not fit for purpose. (maybe a 3.3v board running off a LiPo (as in, directly, at the 3.7~4.2v) would be better? I mean, I know that's what I'd do - you need to take care that it is either not connected to the battery, or that Vcc line from serial adapter isn't connected to board; the safest way to do this is to plug the battery into the 6-pin serial header on the pro mini)

Finally, even if using the Uno as a base were somehow a sound decision (it's not), the 16u2/8u2, at least how it's used on the Uno, is failure prone - just look at how often people post here about how they trashed the serial adapter on their Uno. The uno's have the '328p in a socket, but the weakest link is the essentially non-replaceable 16u2! The CH340G-based clones are a lot more resilient to abuse. And the chip is cheaper. And much easier to solder. I made a CH340G breakout board when I was much newer to electronics. It worked fine, just copy the schematic from the datasheet... Were they worth assembling? Of course not, not with assembled boards running $2 on ebay, but it was good learning, and it got me boards with all the modem pins broken out before I discovered that I could get a CP2102-based board for $2.xx with the pins broken out (no, I don't understand why there aren't CH340G based ones with these pins broken out...)

(why did I want all the modem control pins instead of just DTR for autoreset? The inputs gave me 4 channels of (slow) GPIO that I could view the status of on my computer screen. To say that this made the project I was working on at the time easier would be a huge understatement!)

Many questions here, but they include: How would an ATmega8 work as a USB controller?

Why try and duplicate the design of a readily-available, compact, cheap and tested Nano or Pro Mini? Just why? :astonished:

Why would you use a 9 V supply (what sort?) and a regulator when the board actually runs on 5 V - or 4.5 V from three AA alkaline cells when you do not need USB functionality? :roll_eyes: If you have a serious need (extraordinarily unlikely) to manufacture your own board, the first thing you should do is to omit the largely useless regulator on these designs.