New design using Pro Micro/32u4

Development Boards Arduino
1

I’m building a project and want to use the Pro Micro (sort of). I’ll have other supporting electronics that I’ll need to build a board for. So why not just include the 32u4, crystal, etc on the new board? If I burn the ProMicro bootloader on a 32u4 and implement the same design around the 32u4…

  1. Will it simply be recognized as a Sparkfun Pro Micro?

  2. Will I be able to use the “NOT USED” pins shown in the schematic if I route traces to those pins? Like ADC0 and ADC1. Are they implemented in the software design just not in the hardware on the board?

2

In general the answer is; yes, you can do that. I have done it several times using the ATmega328, but not with the 32u4. Regardless the principle is the same.

More specifically,

  1. Recognized by what? If you are asking if the IDE host system USB driver will talk with your custom board, the answer is yes if you implement the USB interface the same way and program the chip with the same bootloader as the Pro Micro. The Arduino IDE itself does not recognize the Pro Micro, you have to tell the IDE what board you want it to target.

  2. Yes, however you may have to drop back to more primitive access methods depending on what you want to do with each pin. You will need to learn more about the IDE and the ATmega to determine the specific methods or limits.

Good luck with your project.

  • Chip
3

Thanks for the feedback, uChip. Answered about everything.

4

Do you have a ‘bare bones’ (minimal) 32u4 schematic you are following?

I have made several Arduino (and variants) using the ATMega328 chips… but only ‘purchased’ Pro-Micros… (never made my own yet)

5

I’ve been using the ProMicro for code development and prototyping. I haven’t gotten the plain-jane 32u4 yet though. Next step will be getting a tqfp44 breakout board and upload the Leonardo bootloader and see how the code works.

6

cool.

I have a Pro Micro from here, but I picked up some ‘others’ from ebay… (as I got both +5 & +3.3v versions for roughly $4.00 USD each)

been meaning to look up working out a ‘bare-bones’ 32u4 based board… just havent had the time.

7

It won’t be that hard. The Leonardo schematic isn’t that difficult. A USB port, a few passives and a 16MHz crystal. I want to make sure the Leo bootloader works like the ProMicro though. Whereby it starts user code immediately and needs a double-click of the reset to enter bootloader mode.

8

ahh… I see.

I am not sure myself.

Actually I didnt even the bootloader on the Pro-Micros I have… (whatever they came with is what I’m currently running!) haha

Would be good to know though, so please post back your results when you get there.

I’m still working my way through using the Pro-Micro with a USB Host Shield (and getting a USB keyboard to ‘pass-through’ correctly)

9

Good luck with that. I’m just reading a bunch of TMP36s and driving a touchscreen LCD. The PDQ_GFX libraries are way faster than the Adafruit ones.