Electronic – Custom Atmega32u4 board first boot

atmegaavr

I've built a custom board with an Atmega32u4, like the Arduino Pro Micro from Sparkfun.

The circuit seems ok, but when I plug the board to a pc, the usb device isn't recognize (doesn't even pop the "Installing device driver software" bubble).

I'm missing something?
Doesn't the Atmega32 ship with a base firmware installed?

update:

The problem is: using only the internal oscillator, should the MCU be recognized as an USB device when plugged to a computer? If not, what is needed to do that?

Best Answer

From the DFU bootloader datasheet:

The 8bits mega AVR with USB interface devices are factory configured with a USB bootloader located in the on-chip flash boot section of the controller.

This USB bootloader allows to perform In-System Programming from an USB host controller without removing the part from the system or without a pre-programmed application, and without any external programming interface.

The part itself should include a bootloader. Verify that the circuit is configured as per section 21, "USB controller", in the Atmega16U4/32U4 datasheet and that the fuses are programmed for external crystal operation as well as BOOTRST for booting into the bootloader instead of the code at 0x0000.

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