The LEDs that I used had very high Luminous Intensity (MCD) (Yellow at 2-3k; White at 14-16k) for the build. This allowed me to keep the overall power draw for the module down when all LEDs were lit.
The parts that I used are here:
I started with 10k resistors and, with these LEDs, the brightness matched the TT quite closely when at full! (I did, however, ultimately implement a logarithmic lookup table in firmware so that the brightness scaled better over the range of values - but that is another story.)
To be honest, I was just getting my head around all of these details at this point in the design process. @Galapagoose was amazingly kind and helpful … he nearly carried me through my darkest moments of confusion and ignorance. I went back through our PM thread from the time and here were his recommendations from back then (hope you don’t mind my sharing):
Thing is, the mA current rating isn’t a ‘recommended value’ but rather just a test case at which they measure the mcd rating. 10mcd LED @20mA is the same brightness as 100mcd @2mA, but you draw one tenth the power. This is important to help keep noise low in the power system.
The LEDs you linked are 2000mcd which is super bright, so I think you’d be safe starting around 10k for the resistor. If you’re looking for a reference point, I’d aim to have the LEDs be at least close to the brightness of TT just for continuity sake.
Also - think about the situation where all 8 LEDs are on full brightness at the same time. You don’t want 160mA (@3v3) being drawn just to indicate some levels.
These values are very easy to change after the circuit is built. The tradeoff is very simply between brightness and power draw.
Hope this helps!!!