I had a few of these clones (http://www.minikits.com.au/nano-... but from aliexpress) lying around and I wanted to convert them to 3.3V, as I had the ones with the CH340g USB to Serial IC, whose schematics etc are scarce, but from hackaday I found the proper diagrams (http://hackaday.com/2014/12/02/f...) - but no schematic of the arduino nano, I had to play with the multimeter a bit and find out where the power traces were going, this is what I got
yes I forgot to draw the GND connection on the LM1117 5
So I replaced the LM1117 5.0 with the same pinout LM1117 3.3, and removing the diode from the PCB, I added a little jumper wire and ended up something like this
Again forgot the GNd connection, also i had to connect the pin 4 and pin 19 of the CH340G Ic
I also tried then to follow this tutorial here: http://www.ba0sh1.com/tutorial-3... to change the bootloader so that it divides the 16MHz clock by 2 and I get a clock of 8MHz as the datasheet mentions cant run at 16MHz at 3.3v supply BUT, i was unable to program the bootloader, something about no response from the Nano, but then i tried it with the IDE and it is still working..>! i thought okay, the specs in the datasheet must be light about the limits, but I really do need to make it work at 8MHz as I cannot rely on this, though I tested the serial, it is still working...
Also, what will happen if I connect a Li-ion battery, the small mobile ones, (rated at 3.7V but can go to 4 something volts on full charge) tot he VIN pin - I am assuming the Regulator will work, but the problem case I need to ask about is what will happen if I have the USB port connected also and also the battery (dont want any explosions..)
so the battery and USB issue and also why cant I program the bootloader..?? any ideas..?