Need help with a barebones arduino and serial.

Hello I developed a project using a barebones arduino with an ATMEGA328P but didn't include a serial connection.

Is there a way to get the serial messages from this ATMEGA to another Arduino and then forward them to the PC using the RX/TX pins?

This is the scheme I used:

Attach your picture in the forum, most won't dig into some potentially spam (or worse) filled website to look.

Yes, you can use Software Serial on any two pins to send messages to another device.
You can use an external FTDI Basic to send to the PC directly also, using Software Serial also. Just need 2 pins and Gnd.

You can use I2C to send to another device if A4, A5 are free.

@supernovadml, If the only purpose of the other Arduino is to act as a bridge to a PC then I think (but I have not tried it) you just need to connect the Rx and Tx pins of your Atmega 328 to the Rx and Tx pins (NOT crossed over) and then USB communication will pass through to your Atmega 328. Also be sure to connect the GNDs.

When I make a barebones Atmega 328 I use a USB-TTL cable to connect it to my PC.


If you don’t want the 2nd Arduino in Robin2’s to be active, connect it’s Reset to Gnd also. Then you can use the USB chip of the 2nd board.

Of course, if you haven’t used the 1st board’s ICSP connections to download a bootloader first, the serial connection may not work as expected.

This is looking like a very painful way to do the job of an inexpensive Nano (clone). :cold_sweat:

I've never used or owned a Nano. Promini, sure, FTDI Basic, yes, and a couple of Programmers. Can make up any version of '328P based board with that, or from bare chips and a crystal and a few caps, and a resistor or two.

Well yes, of course the Pro Mini and an adapter is a sensible way to build a product that does not require continued connection to a PC and indeed it can be argued that there is not a great deal of application for an Arduino as a mere attachment to a PC because the PC is overall more capable. You can just use a USB-parallel interface cable to do many jobs.

But where you do want to use an Arduino as an attachment to a PC, such as to interface to I2C and “one-wire” sensors such as the DS18B20 - the broad category of tasks requiring “real-time” control - then the Nano is the single unit purpose-built do do that with the USB interface included.