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Topic: Using ATMEGA328P Standalone (Read 579 times) previous topic - next topic


Good afternoon all,

I was wondering if anyone could shed some light on a option for my project.  I have an Arduino UNO R3 and I am developing a tool for fault insertion into a system. 

Once I get the program running successfully, I would like to remove the ATMEGA 328P from the UNO board and place it on a board that has the necessary support circuitry (for me, this is mainly a crystal.  I have seen this done before, so, obviously it does work.

One issue I am worried about is the serial interface.  I do need to connect to a computer via a serial interface.  I assume that the interface on pins 1 and 2 will still work.  I realize I may need a level converter if the serial signal is actually RS-232 from the computer.

Any insight or experience would be greatly appreciated.

Rob Hix


These days this is typically interfaced with a computer using a USB-serial adapter that creates a virtual com port on your computer. You can buy the breakout boards (FT232,
CH340, etc.) or just add the necessary components right on your board. If you prefer a true serial port that's also possible.

This is a good tutorial for ATmega328P on a breadboard, which could be easily adapted to a custom minimal board:
It shows how to connect the USB-serial adapter with the auto-reset circuitry, something that is not shown in the official Arduino tutorial pages.


Do not forget the 0.1uf power supply decoupling caps Vcc to ground and AVcc to ground. 


Jul 16, 2017, 09:12 pm Last Edit: Jul 16, 2017, 09:18 pm by Johnny010
I have used MCP2200 USB drivers/Interface to allow USB serial to my PC.

You can buy like standalone USB Serial/TTL converter things but I like having it all on one PCB.

I use the ISP 6-pin port for programming.

The MCP2200 only needs 2 connections to the ATMEGA328 (TX-RX, RX-TX).
It needs the two data pins going to the USB plug (D+ to D+ and D- to D-).
Optional LEDs for "traffic visualisation" on 2 pins.
Needs a 12MHz crystal and 0.1uF caps.
Recommends a "ferrite bead filter" on a wire connecting the USB plug +ve to the PCB to filter noise from PC.

The ISP (in system programming) pins are just a basic 3x2 pin header that directly connects to the ATMEGA328 for programming.

PS/EDIT: There is a way to hve it so that the MCP2200 can be used to program the ATMEGA328 via the USB port...but I have not got around to that/understood it yet.

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