Atmega32u4 not detected on computer

Hi recently I have tried to design an atmega32u4 with micro sd card board to be plugged in via usb and simulate a keyboard. I got all the bits and my soldering is fine but it isn’t detected by my windows 10 home edition or my computer’s bios. I’ve soldered another board to get the same problem. The chip is brand new from lcsc.com (Microchip Tech|Microchip Tech ATMEGA32U4-AU|ATMEL & AVR|LCSC). I have not touched the bootloader or fuses. My schmatic has been uploaded.

Schematic_arduino beetle_2020-09-18_11-50-51.pdf (73.5 KB)

Do you have an external xtal?

windoze_killa:
Do you have an external xtal?

Yes I do X2 16mhz connected to XTAL1, XTAL2 and ground throught two 22uf capacitors

I could not find any indication from the quoted site that the Atmega32u4 chip has actually been pre-programmed with a bootloader.

If not. you will need to first burn a bootloader to it using an ISP programmer. An UNO or similar works fine.

Willem.

Willem43:
If not. you will need to first burn a bootloader to it using an ISP programmer. An UNO or similar works fine.

Okay thanks I'll try that.

windoze_killa:
Do you have an external xtal?

Should the XTAL have a oscillating voltage between one side and GND? It registers nothing on my multimeter.

Should the XTAL have a oscillating voltage between one side and GND? It registers nothing on my multimeter.

If the chip has in fact not been pre-loaded with a bootloader it will be using the internal crystal clocked down to 1MHz. I do not think you will see anything on the crystal under that condition (I am speaking under correction here but I do not think the crystal is driven when using the internal clock. I have never checked the external crystal when running on the internal clock - definitely not using a multimeter).

I usually burn a bootloader initially using the internal crystal (at either 1MHz or 8MHz) to make sure I can communicate properly using the programmer and then upload a simple blink via USB (in the case of a 32U4). Only then do I switch to external 16MHz (re-burning the bootloader to set the fuses correctly) which confirms the crystal working.

Hope that helps.

Willem