avr 328p, crystal and leds

[sjomae]

If a crystal is used, this does make DDRB unusable for using it for the LEDs, as in the book? Or is there a trick to make it work?
The crystal is covering up the PB6 and PB7 pins.

Related:
#24

[hexagon5un]

Hi,

Yes it does -- those two pins are dedicated to the crystal oscillator amplifier internally, so if you use a crystal you can't use them as GPIOs.

For learning, I thought it was useful to have a full 8-bit block of GPIOs available. It makes the whole "write to a register, and corresponding LEDs light up" much more intuitive.

But when you need more speed, you can get it by using those two pins for a crystal.