Running Beetle (Arduino) at 3V/6MHz

Other Hardware 3rd Party Boards
1

Hello friends,

I have recently got a "Beetle". Per specs,

  • clock speed: 16MHz

  • Supply voltage: 5V (operating Beetle at voltages below 4.5V reduces the reliability of the board)

My question is if I have to move to a 3.3V supply, do you think the following solution will provide more reliable operation?
Proposal: disconnect the external 16MHz xtal and let ATmega32u4 run on its internal 6MHz internal clock and supply the chip with a 3.3V supply (reducing power while reducing the clock speed to enhance reliability). Thanks for your feedback in advance!

2

Keep the 16MHz connected and first set the fuses to use the internal 8 MHz clock. Next you can disconnect the 16MHz crystal; but this would be the very last step after you have taken care of the below.

  1. When your board runs on 8MHz instead of 16MHz, all your timings will be wrong.
  2. The board will no longer react on a software reset; this happened to me with a SparkFun ProMicro 3.3V/8MHz when I programmed it as a Leonardo (5V/16MHz).

What I would try

  1. Create a board definition for a 8MHz 32U4; you might be able to use or base it on the SparkFun AVR board package (it contains a board definition for 3.3V/8Mhz external crystal).
  2. Modify the fuses in the board package to use the internal 8MHz crystal.
  3. Burn the bootloader using the new board definition.
  4. Upload a simple sketch using the new board definition; this can be the Bare Minimum to verify that you can upload and that the board is still recognised after that.
  5. Try some more basic sketches.
  6. Remove the 16MHz crystal.

I have no experience with the beetle but I think that the above will work.

1 Like
3

Thanks! All great points.
Going through your considerable points, this came to my mind to keep the external XTAL and change the time scale to reduce mcu clock and therefor voltage :+1:

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