Hi,
Our school department has a bunch of Pro Micro 5V/16MHz and we are moving to 3.3V for any digital/uC lab work. Can we run them at 3.3V? I expect that we might have to change the boot to reconfigure the clock to 8MHz, but is that the only barrier?
Hi Louis.
The 5 volt boards run at 16MHz and technically it’s out of spec to run them at 3.3 but extensive testing has shown that they work just fine at the lower voltage. No need to change anything in the IDE, you still want to select the 5 volt board even though you’re running them at 3.3. (The IDE takes into account the difference in clock speed and makes adjustments that will break some code if you select the wrong voltage.)
Keep in mind that if you have 3.3 volt only devices attached too them you’re going to want a 3.3 volt FTDI to program the Pro Mini’s since there’s no voltage regulation when programming through a FTDI. The 3.3 volt FTDI will work just fine on the 5 volt board.
FTDI? I was asking about the Pro Micro with the 32U4 uC. Thanks.
My mistake, I though I saw Pro Mini. Too much multi tasking!
Same goes for the Pro Micro, you can run the 5V board at 3.3 and you must program it as the 5 volt board in the IDE or you will brick the board. The real issue with the Pro Micro is that when you plug it into USB, it’s going to apply 5V to the VCC lines so if you have parts that are not 5 volt tolerant, you will want to disconnect those from the Pro Micro before plugging into USB.
Honestly, it might be easier to get 3.3 volt boards but the 5V board will still work when powered by 3.3 volts.