Schematic Check Needed Please.


(im not sure if there is a section here just to get feedback on schematics or not?)

being new. .I am trying to get ‘used’ to Eagle… and laying out schematic properly (instead of using photoshop and block style diagram… which I know most of you experienced people loathe!) LOL

while Im slowing getting used to the layout a bit… some things still elude me… (as well as just normal workflow operations, copy, paste…etc…are just non-intuitive at first)…

Im still very RAW in the PCB layout portion… and have been trying to work in the schematic editor first… following tuts… googling certain questions… reading manual and tutorial pdf’s…etc…etc

instead of just fooling around…I gave myself a mission, a goal if you will, to work toward. This way i can deal with the normal problems/questions/errors that arise during a normal project.

I opted for (trying) to layout a schematic for an SMDuino w/SD socket type circuit/end result…
using other schematics as motivation and learning… and other minimal Arduino circuit image…etc…

Feeling a bit overwhelmed here…as not only is Eagle new… Im pretty raw in electronics/principles itself.

If anyone has some time please take a look at my first schematic attempt in Eagle… and if you see some errors or have some tips/advice… its appreciated. (please do not come in here saying/asking WHY this or that was done… or talking down about what was done… if its not obvious ‘why’… its because Im new and dont know better yet, hence learning and trying and getting feedback) :wink:



-I need to learn/break habit that not all lines need to be connected in the schematic… I can draw lines out… and just LABEL the net…correct? (which is common/custom for big schematics… right? as not all components and parts can fit together in same place… so they space out over the schematic page?) So I can just draw a NET from a pin and stop… give it a LABEL/NAME and it will know it supposed to be part of that ‘NET’?

SMDuino_SD.sch (535 KB)

Srry I can't look at it, I use kicad and im on my phone anyway, but in kicad(which im sure works for eagle) that technique of labeling the net on watever you want connected without physically connecting it works fine, and is especially easy if multiple connections need that net or its confusing if you draw it out Kinda like the power nets, you don't connect them all together just ad a 5v label or ground etc,


Im hoping it all works.. (takes a bit of time getting used to) =(

I re-uploaded my schematic... I had forgot to add in the NETS for the rest of the pins on the Arduino (Analog and Digital pins broken out)..


Start the pcb layout yet? That's the fun part, I always challenge myself to fit it in with just enough space to fit components(using both sides), using the widest traces I can while keeping attention to any special ones(analog inputs, clock,etc) it helps when you pay for sq.inch so its cheaper

I have NOT started the PCB part yet..

kinda waiting for some feedback.. dont want to get TOO ahead of myself.. LOL

(but I want to.. it seems to funnest part!) LOL

Im forcing myself to learn Eagle.. cause now I have to wait for help..and it takes a long time to make simple fixes..etc..

(trying to learn to fish and all that!) LOL

you look at schematic yet?

You need a voltage level shifter for signals coming out of the uF to the uSD to keep them <=3.3V.
Check out TXB0104, from as an example.


I'll check out link now...

also.. did the board we did have the level shifter on it? I didnt think so? how was that done? (voltage divider using resistors?..but I didnt see any odd values used?)

I thought having the 3.3v vRegulator would help..but still signals from the Arduino are at 5v.. is that right?

Yes, Arduino at 16 MHz needs 5V, and outputs 5V signals. Prior board: - uses 74ACH125D chip for the level conversion - has both 5V and 3.3V regulators

This is a link to a good tutorial about diy pcb's using eagle:


oh the buffer chip, right? I thought that was just for the SD/DAC (audio stuff).. and didnt do any lever shifting..


I'll check out the TI chip/version for this.. and then see if I can:

1.) make or find a symbol/device/package for this part

***(Ive done this once or twice before... as well as learn to take schematics and make libraries out of it.. (nice for me on learning when I need a specific part, but cant find it in any library) ...and make/save these to my own custom library.. (wasnt easy...haha.. not even sure I got it all 100% correct)

2.) read data sheet and see if I can figure out to add it to my schematic/pcb..

(this gives me a goal to work toward)

I'm having no luck opening that schematic - what version of Eagle is it from?

Eagle version 6.2

thanks for checking (trying) ;)

bump.. anyone? any feedback?

I think I have errors in the schematic portion...

1.) Im unclear as to the AVCC, VCC, VCC & AREF pinout... is that correct? I copied some of it from another schematic... trying to morph a minimal circuit.. with some other designs/additions I have seen in other projects.. (DTR...etc)..

So Im not sure if I have been doing the schematic portion correctly AT ALL??? like the 'nets' and the LABELS? is all that correct as well??

2.) when I go into the PCB editor portion... I see all my components.. and I start placing them.. but the UNROUTED layer/lines is driving me crazy!.... I keep thinking I have a ton of errors as I see double lines on like component A going to the same component B?

3.) I thought I had attempted to place some V+ & GND symbols in the schematic.. so I can make some 'battery' +/- pads...

but they dont show up? (maybe use a component footprint for the pads or something??

Im going to go check out the lever shifter chip now.. (hopefully there is an easy to find eagle part for it!!)


There should be a footprint for a plain pad, or you could make one or place a pad after the fact and give it a net


any idea on the double 'line' thing when viewing the un-routed layer in PCB mode?

I can upload it you like/need be.


"double-line thing" You can select View:Layers. and deselect the Unrouted layer, they will stop appearing. Or click the Rats Nest button (lower left, looks like an X), that will connect traces to the nearest components.

Usually(in kicad atleast) those lines are just for you to see what goes where, to help place components for easy routing I think you can disable/hide it with a button or setting id look over the whole thing but unfortunately kicad can't open eagle files

hi guys…

thanks for the replies…

(Crossroads - you get my emails last night/today?)

Im not sure what RatsNest will do? connect to nearest component?

I was toggling the unrouted layer… but was curious as to why say resistor A would have 3 lines going to cap B for example…

I would understand 1 line to each side of the resistor/cap… but why would one side have 2 lines going to one side of the cap (just a general example of what i was seeing)…

it lead me second guess myself… and think the schematic portion was incorrect (which is was… but not showing multiple lines…etc)

anyways… here is my second iteration of a SMD based Arduino circuit with uSD socket on board… (maybe similar to a pro-mini or something with uSD on bottom)

(still have found an Eagle part for the level converter)…

feed back on the schematic (if things are wrong… or better things to do/document?)…

as well as how realistic setting up a board like this would be…

thanks! (54.2 KB)

Here is another version… (latest attempt…LOL)

I believe I have found the leveer converter chip/package for eagle…

(I hope I hooked it up correctly)??

I ‘think’ I have thing the schematic correct? (if anyone can verify?)

I have the PCB dimensions… and my parts positioned on the stage…

and thats about as far as I am!..

learning alot… getting more comfortable using Eagle… finding/using/re-using parts…others schematics.etc…
(the library/add still kills me to find anything!)

What is next?

I believe I have also correct/fixed all warnings and errors given when in the schematic editor as well!..

Do I click on the auto-route button next or something?

thanks for looking and feedback is appreciated!

take care! (56.2 KB)

I got the files, but not until after midnight. Went to bed shortly after.

SMDuino, looks like normal unrouted board to me. All the criss-cross lines are an indication that your parts placement needs adjsuting. You want to minimize those, or will have a hard time getting it all connected. Reassigning IO to the connector pins may help there.

The signals on the ICSP connector are not correct - you need SCK (D13), MISO, MOSI there. The Green names do not make the connections.

Download the Sparkfun library into your eagle lbr folder. They have a component under M02, called M02PTH, that fits perfectly instead of the diode pads. Will be less likely to rip the wires off the board that way.

U2 needs ground connected. U1, U2, read their data sheet, might need to connect the enable pins to their Vin pins. C6,C8, 10nF seems kinda small - I'd go with 100nF. Select each component on the schematic, drag it up or down a little - make sure all pins are actually connected to the trace next to them. Also run the Tools:Erc check, will help you find those too. U4 for example.

When done moving parts, draw a polygon (Draw:Polygon) around the board, one each top & bottom, right-click each and Name them GND. Will help with getting everything connected.

Man, 11:30 already. Will see what I can do with the other one.