ATMEGA328P Development board

I'm planning to make an ATMEGA328P development board.

I'm new to electronics. Schematic is shown in the image.

  • Please let me know it is correct or not, and please let me know if any changes or suggestions required.
  • Please check the LM7805 part also, and also let me know if anything should be taken care of during PCB design (planning through hole?)
  • 1
    \$\begingroup\$ No time to write a full analysis, but immediately I see that C4's upper terminal is not connected to the 5v0 net. \$\endgroup\$
    – nanofarad
    Sep 29, 2020 at 16:37
  • \$\begingroup\$ Hiii yes , thanks I'll update it \$\endgroup\$
    – Anil Suha
    Sep 29, 2020 at 16:44
  • \$\begingroup\$ The Seeduino Arduino clone has a nice feature you might want to implement. It can switch between 3.3V and 5V VCC. It's very handy. Also you might want to add (on one or two pins) a zero ohm resistor and a not mounted resistor to ground. That way you could easily divide a high voltage to VCC range directly on the board. \$\endgroup\$
    – Dejvid_no1
    Sep 29, 2020 at 20:09
  • \$\begingroup\$ U9 pin 7 (VCC) and 20 (AVCC) connect together, but seem to be missing the connection to the actual power supply \$\endgroup\$
    – MarkU
    Sep 29, 2020 at 23:12
  • \$\begingroup\$ Hii MarkU thia is a serious mistake. Thanks for spotting. \$\endgroup\$
    – Anil Suha
    Sep 30, 2020 at 2:39

1 Answer 1


A development board should be forgiving. Thus I recommend to add protection against most probable errors like wrong polarity of VCC as well as overcurrent protection to the GPIO (PTCs, limiting to 20mA). I'd also not use a crystal for development. Internal oscillators of IC are sufficient for development. They'd be only necessary when using baud rate crystals for high speed serial communication or if you really need the 20MHz.

If the latter were true I suggest to use a more recent ATMega chip with additional periphal features like built in DA converters or improved AD rates.

Maybe you outline more clearly what »development« means in the context of your circuit.

Dirty details:

There are features like oscillator calibration and individual capacitance of traces to XTAL that maybe require other Cs than 22pF. I'd also put in a spare/ socketed level translator or hex-buffer for I/O lines connected to other devices – saves the µC by sacrificing a ten-cent-part.

And AREF shouldn't travel all around the final layout or be mixed with all other signals. Instead you want a short trace with a ferrite bead/ inductance and good decoupling also from digital ground. The cheapest thing I often do here is a reference in a TO-92 case, e.g. LM4040 or LM385. And I prepare a few voltage dividers to be populated as needed and solder joins for AD0-3 inputs.

  • 1
    \$\begingroup\$ Yes and no. The MCU is cheap and robust enough that no one puts external protection on I/Os for this type of board - this is basically an Arduino, and look at the abuse those are subject to and survive. Providing for an external crystal oscillator on the board makes sense, one can chose not to use something that is installed or has a footprint (indeed, internal oscillators have gotten quite good), but it's a lot harder to add something to the board later if the internal oscillator proves insufficient. Considering the ATmega4809 instead of the 328p would indeed be worth some thought. \$\endgroup\$ Sep 29, 2020 at 18:00
  • \$\begingroup\$ I expect a hidden detail revealed later…if an Arduino would be sufficient, why not using an off the shelf socketed R3 board? Instead layout training for education throws in the extra parts. Most of the »development layouts« I admire solder 3-7 components directly to the IC with a bit of glue in case of vibrations. With a bit of practice this is easily layed out on a perfboard, no need for a layout process. (I personally prefer the ones with 3 holes connected instead of full strips.) \$\endgroup\$
    – motzmann
    Sep 29, 2020 at 18:20

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