32U4 Micro hardware serial not functioning correctly

Hey all! I am new to this board but have been happy so far. I am trying to control a camera with this board through some very simple serial commands. The code works fine on my UNO and other boards but the 32u4 Micro doesn’t seem to be outputting anything on the USART Tx line. I get echo (in jibberish) back through the serial monitor when plugged into USB but nothing coming from the hardware serial line. Hooked to a scope I see no change even with USB unplugged. Do you have to enable this some how on this board? I have also noticed that when I load a program that utilizes serial commands the onboard LEDS are very dim even on a bench supply. The board is only drawing around 30mA so I doubt there is a short somewhere. If I load a blinky sketch from Arduino they work just fine on USB but not on independent power? Related, who knows?

FYI I have tried this on two different boards purchased several months apart so I doubt I have a bad board, each were brand new when attempting this code. What am I missing?


If the code works with your Uno and not the A-Star 32U4, I suspect you are using Serial instead of Serial1. The A-Star 32U4 controllers are based on the Arduino-compatible ATmega32U4 microcontroller (the same one as the Arduino Leonardo), so if you want to use hardware serial on pins 0 and 1, you need to use Serial1. You can find more information about the hardware serial on Arduino’s “Serial” reference page.

If you still have problems after trying that, could you post a copy of your code that demonstrates the problems as well as some pictures of your setup that show all of your connections?


Yes, thanks, I figured that out this morning after taking a better look at the datasheet. Everything works fine now!

1 Like