What beginners mistakes have I made?

Sorry if this is incorrect forum/basic question. While I have a background in programming and some experience with FPGAs the I didn't know much about EE before. I run into a hobby project for which I'd like to create a PCB and soon I found myself in deep waters. So I decided to step back and create a simple PCB to learn basics. I tried to create a simple AVR board with an GPIO header, JTAG connector and USB-to-UART bridge. I've created something but I'm sure I've done many basic mistakes and strange decisions so I'd be grateful for pointing them out.

PS. I know there is no power switch but I couldn't find one on with eagle library.

shabaz over 8 years ago in reply to mpiechotka

(By the way, if you need mounting holes, don't forget to add them.).
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shabaz over 8 years ago in reply to mpiechotka

Hi Maciej,

That looks great!
Regarding 'run length', I only use it to check for unrouted airwaves, I've never checked to see if the resistances look accurate. I just use a PCB trace calculator if I really need to do that, but for a microcontroller project, I'll stick to things like 8-10mil for general traces, and then use a power plane, or something perhaps around 16-24mil to get power from the supply to the microcontroller (and have the 100nF capacitors close to the microcontroller, like you have).
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genebren over 8 years ago in reply to mpiechotka

That is look great I like that you entered the FT230XSFT230XS from the opposite side thus avoiding the crossover vias very nice(I may have to try that if I re-layout my board
Gene
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mpiechotka over 8 years ago in reply to genebren

Thanks. I think I'm starting getting the basic rules (I restructured the board so it fits in 2" x 3").
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mpiechotka over 8 years ago in reply to shabaz

I knew and use DRC - you can often download DRU files from PCB manufacturers websites to get more specific rules for that particular one.

While looking for the command I run into length_freq_ri and my 3.3 V signal (from current iteration of board) has R of 861.49 mOhm (I don't think the tool have 5 s.f. accuracy and at least 3 numbers are 'fake'?) and GND, despite being pour, 156.43 mOhm. Are those numbers reasonable or should I be worried (I don't know how much 'resistance' IC has[1])

[1] I put in quotes as I know IC are not linear so word resistance doesn't really applies here.
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genebren over 8 years ago in reply to mpiechotka

This is looking a lot better. Funny, that the pin-out of the microUSB and FT230X require a crossover on the D+/D- signals. I used the same combination recently and was annoyed that I had to use vias to cross the two signals.
Looking good!
Gene
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mpiechotka over 8 years ago in reply to genebren

Is there any script to 'fan out' (I know the term means something completely different)? I tried to rotate the header but I still get the bunching up:
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eagleenthusiast over 8 years ago in reply to shabaz

Shabaz,

Thanks! That is totally understood.
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genebren over 8 years ago in reply to dougw

Just a quick FYI, but the USB is not supplying power to the board, but only providing a signal when the USB is plugged in, via the bus sense. There should not be any excessive current draw.
Gene
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shabaz over 8 years ago

By the way Maciej, since you're using EAGLE, be sure to run the design rules check (DRC) too, and also _never_ forget to type 'run length' in the EAGLE command line, before you feel you are ready to submit the PCB to the factory (you'll only make this mistake once : ) That command will tell you if you've forgotten to route an air-wave.
I'm not very good at intuitively routing PCBs, so for me what works is approximately routing things, and then ripping up and re-routing traces to tidy them up. Basically I manually do two passes.
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