Bear in mind that a single IO is sinking all of the current for segments- so using 390ohm resistors might result in far too much current being sunk through that pin.
If that calculator is correct, then 5mA * 8 segments would result in 40mA- waaay too much for a single pin to sink.
I believe 600Ohm is the lowest you’ll get away with.
Ah, I’m working on this right now, 390ohm resistors in place, I’ll swap them now, thanks, you saved me frying my LEDs :-)
Hi again @gadgetoid, please could you share a bit more info on how to hook up the 4 cathode / digit leads at the Pi end?
I understand that this can be configured just using the extended GPIO pins, but I don’t see any pins corresponding to 0 and 1 there (though there is GPIO 5 and 6).
http://pi.gadgetoid.com/pinout/0v-ground
Any help appreciated, thanks!
I was naughty and used the EEPROM ID_SC and ID_SD pins which I think are 1 and 0 respectively. You could use GPIO 7 and GPIO 8 instead if you want to avoid these, but I was trying to squeeze everything on just the extra pins.
Thanks, I would like to leave my Displayotron insitu too, so I’ll try the same as you :-)
Just for completeness sake there is a good wire guide and code for the display from sparkfun that works on ardunio
https://learn.sparkfun.com/tutorials/bubble-display-hookup-guide?_ga=1.66485742.13368589.1417454515
I can vouch for it working