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mrehkopf / sd2snes

SD card based multi-purpose cartridge for the SNES
http://sd2snes.de
GNU General Public License v2.0
590 stars 115 forks source link

LED Brightness #88

Closed kylophone closed 5 years ago

kylophone commented 6 years ago

The LEDs can be overbearingly bright during use. It'd be nice if there was a configuration to either control the brightness of the LEDs, or to turn them off completely.

mrehkopf commented 6 years ago

Conveniently the firmware can already do this. Now I just need to expose it via a configuration option.

kylophone commented 6 years ago

Awesome. This is a simple little feature, and it would be much appreciated!

ramapcsx2 commented 6 years ago

In some cases (cart shells I mean :p), the LED is not exposed and has to shine through the plastic. If I wanted to make it brighter, I realize I would have to change the current limiting resistor. Is there some value on how low one can go for these?

@kylophone If the LED is too bright on a product, may I suggest the good old CD marker? :)

mrehkopf commented 6 years ago

I am not sure what type of LED krikzz is using, I think he recently switched to a very bright type with no diffusion (clear body). Resistors are 680 Ohms by default, I had originally used low power LEDs @ 2mA each. You could also thin the cart shell a bit from the inside =)

mrehkopf commented 6 years ago

Seems that fairly bright LEDs (900-2800mcd) have a forward voltage of around 1.85-2V at 20mA, so if you calculate your resistor to drop 1.5V (3.3V-1.5V=1.8V) you should be fine. So the smallest "safe" resistor should be around 1.5V/.02A = 75 Ohms. However, at the full 20mA the LEDs will contribute significantly to the total power consumption of the sd2snes (~100-120mA).

ramapcsx2 commented 6 years ago

Thanks! I appreciate the formula and ballpark figure for the resistor :) The shell has already been thinned out and it helped a little. The LED can be seen in low light conditions now. I'll try to get the LED current to maybe 5 to 10mA and see if that's enough for daylight visibility. By the way, I'm only interested in the save / load LED. It's nice to see at what point a game actually writes out a save game :)

kylophone commented 6 years ago

@mrehkopf, I can take a crack at this myself. Is there a place in the code I should be looking at?