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[on:]

Just gone to order some ATMEGA32U4 ICs from RS to make my own boards up but they have both ATMEGA32U4RC-AU & ATMEGA32U4-AU with the NON "RC" variant costing £3.66 in 10s or the "RC" ones at £3.98

When I go into the RC variant's page and click for the data sheet it brings up the same one !

So is there any difference and do I need to get a specific one?

I'm looking at messing with them to create a MIDI device and a Keyboard emulator etc to the USB is the important bit.

[Reply #1 on:]

Check section 33 of the datasheet:

Ordering Code            Default Oscillator
ATmega16U4-AU         External XTAL
ATmega16U4RC-AU     Internal Calib. RC

6.2.1    Default Clock Source ATmega16U4 and ATmega32U4
The device is shipped with Low Power Crystal Oscillator (8.0MHz-16MHz) enabled and with the
fuse CKDIV8 programmed, resulting in 1.0MHz system clock with an 8 MHz crystal. See Table
28-5 on page 348 for an overview of the default Clock Selection Fuse setting.

6.2.2     Default Clock Source ATmega16U4RC and ATmega32U4RC
The device is shipped with Calibrated Internal RC oscillator (8.0MHz) enabled and with the fuse
CKDIV8 programmed, resulting in 1.0MHz system clock. See Table 28-5 on page 348 for an
overview of the default Clock Selection Fuse setting.

[Reply #2 on:]

Cheers....  So which one do I need to build my own Leonardo boards running at 16MHz?

Many thanks..

[Reply #3 on:]

I think either one - you are going to change the fuses to use 16 MHz external oscillator anyway, yes?

[Reply #4 on:]

That was the plan yes.