Arduino UNO and Nano CH340G Schematics

Using Arduino General Electronics
21

Thanks, Pert!

22

Just why do you want 3.3 V?

Well, yes, it is a pdf, not an image file which can be viewed in the thread.
However ...

Selection_052
Selection_0521509×1009 126 KB

23

First I've ever heard of a DHT11 not operating at 5 V! :roll_eyes:

Well, for things like the NRF24L01, you certainly do not want to try and use the 3.3 V reference output from the CH340 so yes, you need the proper regulator.

The circuit described is pretty much a Nano clone. The "elephant" question is of course, why are you attempting to re-invent the Nano? Not a profitable exercise when there are (or were) Wuhan sweatshops doing it cheaper! :astonished:

24

That schematic looks OK. Just be sure to add 100nF decoupling caps to each VCC pin on the microcontroller.

25

Well, Its just about the cosmetics actually
wanna have something that others don't :slight_smile:

26

So there are 2 vcc pins on the atmega328p-pu
I have to add the 100nf cap to both of it?

27

Its maybe too many numbers that I put there, but just tell me which number will need the 100nf cap.

Selection_052
Selection_0521509×1009 162 KB

28

So, where should I put the 100nF cap?

29

#1 and #2, on the pcb physically close to those pins.

30

Ok, I'll add them

31

Like that?

Schematic_ZEROBOARD UNO_2022-03-28
Schematic_ZEROBOARD UNO_2022-03-281500×1001 107 KB

32

Yes!

33

ok thxx

34

PS:

  • your TX led may not be as bright as the RX one because of the 1k resistor in series with the TX line; not a huge problem probably as these smd leds are pretty bright at low currents already.
  • I've had an occasional problem with a microcontroller going into high-voltage programming mode due to a very short discharge peak on its Reset pin. A diode (pretty much any kind will do) with its anode to reset and cathode to Vcc solves the problem.
  • You'd have to check, but if my memory serves me I believe that the recommended capacity on the V3 pin of the CH340G is 10nF, but I'm not 100% sure on this. Also, even if it is, 100nF will probably work fine...
  • In laying out your PCB keep in mind that USB D- and D+ form a differential pair. As a consequence, you should try to keep these traces equal in length. It's common to route them side by side and make a little curve in one of the lines to compensate for small differences in length. These are the wiggly traces you sometimes see on PCB's. See here for an extreme example:
    https://www.orcad.com/sites/orcad/files/routes.png (source: Cadence/Orcad)
  • Also for the crystal oscillators: keep them close to their respective chips to keep traces short, and keep noisy traces (e.g. power supply) as far away from them as realistically possible.
35

How about I just give you the Gerber?

36

You do realize that I've put 100nF caps all around the other components between VCC and GND right? (AMS-5.0, AMS-3.3, CH340G)

37

Just to make sure..

38

No thanks :slight_smile:
I'm saying stuff so you can decide if you want to learn about these things and work them into your own project. I quite like laying out a PCB once in a while, but for my own projects.

Yes. It looks good; no comments on that. But it doesn't relate directly to the things I've said in my 'PS' reply.

39

I don't really understand this

40

So, should I route them side by side or not?