BBC:Micro LED brightness

[Timmmm]

Just a quick note about this:

I was getting inconsistent brightness when driving LEDs directly from the microcontroller’s digital I/O pins and don’t know why

I would guess the reason is that the nRF51 can only drive 0.5 mA from its GPIOs unless you put the pins in 'high drive' mode. Then up to 3 pins can drive 5 mA each.