Micro pro convert from 5V version to 3.3

Development Boards Arduino
1

I bought 5V version of the Micro Pro board and now I need convert it to 3.3V.

I know that I must change on board voltage regulator to 3.3V variant (LG33)

And also J1 must be disconnected.

But how to change frequency from the 16 MHz to the 8? It is possible do this only by write bootloader for the 3.3 variant?

2

tprochazka:
But how to change frequency from the 16 MHz to the 8? It is possible do this only by write bootloader for the 3.3 variant?

Correct. You also need to remove the resonator (Q1) and caps. You just need to burn the 8MHz bootloader.

3

Thanks.

Just remove Q1 and caps? No replace?

Bootloader is neccesary burn before or after remove Q1 or it it doesn’t matter?

4

Change the regulator, then remove resonator and caps… The MCU has a built in resonator that will run at 8MHz. Burn the 8MHz bootloader after you have completed the modifications. This bootloader will set the correct fuses.

5

Thanks you very much

6

Sorry to bump this thread after such a long time. Are you sure about the 3.3v version not needing a resonator? All the schematics and photos seem to suggest that the 3.3v version has an 8Mhz resonator.

Also, is it possible to program the new bootloader via USB, or must I use an external programmer?