HW serial connection and uploading a sketch

Hello folks,

I want to design an own PCB with an Atmega32U4 and two serial connections (UART).
I already tried to implement two software serial interfaces but I didn't work at all.
Currently my project (still on Arduino Uno/Atmega328p) is working fine with my current configuration (1 HW UART and 1 SW UART).
But as soon as I want to upload a new sketch I have to disconnect the RX pin on the Ardunio Uno in order to get the code uploaded.

Now my question is:
Is this issue also present on the Atmega32U4 and if yes, how to avoid this problem on my new PCB where I cannot simply disconnect the RX pin on the Atmega32U4?

Thank you very much in advance.

Kind regards
electricar

The ATmega32U4's Arduino bootloader can receive new programs over the USB connection, so you can use the hardware UART for other things.

Pieter

The 32U4 has only one UART. That might be a problem for you if you expect two.

PieterP:
The ATmega32U4's Arduino bootloader can receive new programs over the USB connection, so you can use the hardware UART for other things.

Pieter

Hello Peter,

according to this post:

The USB connection (for uploading sketches etc.) is routed to the same pins internally (RX and TX).

That's why I have problems on the Ardunio Uno and am wondering if the same problem exists on the Atmega32U4 (Arduino Leonardo)?

aarg:
The 32U4 has only one UART. That might be a problem for you if you expect two.

Hello aarg,

I don't expect it to have two. One is HW and the other will be SW serial.

That's why I have problems on the Ardunio Uno and am wondering if the same problem exists on the Atmega32U4 (Arduino Leonardo)?

That is why he told you it wasn't. You do not have the same problem.

according to this post:
serial - Why can't I upload a sketch while other components/devices are connected to my Uno? - Arduino Stack Exchange
The USB connection (for uploading sketches etc.) is routed to the same pins internally (RX and TX).

That mentions the Uno. It does not mention any other board so you jump to conclusions.

It's good to ask if not sure, but the above does (as said) not apply to the Leonardo. Look at the schematics and check the differences.

Ok thank you guys! I was a little confused, now it's clear :slight_smile: