In the new What's a Multicore Microcontroller? text there is a chapter on the 7-segment display. In earlier chapters with discrete LEDs, the current-limiting resistor was 220 ohm. For the 7-segment they are 1k ohm. Why the difference?
For discrete LEDs that use 220 ohm: 3.3/220 = 15mA per LED. With 8 LEDs total =120 mA
For 7-segment that uses 1k ohm: 3.3/1000 = 3.3 mA per segment. With 8 segments total = 27 mA.
Limit total drain on Propeller?
Datasheet says Mx per pin = 40 mA Max. total = 300 mA.
So does not seem to be a problem with 220 ohm.
LEDs more efficient?
Perhaps the LEDs in segments are bright enough at 3.3 mA; maybe even blow at 15 mA. Discrete LEDs barely glow at 3.3 mA.