This is a post I made on my site but I think it will be of better use here so I'll duplicate it here.

How does the Ring of Light work?

Well, MS has made sure to make it as complicated as possible. To save I/O:s on their mcu they have chosen to use a pwm scheme that brings down the pin count from eight to five I/O:s. If you want to understand how this works you should first read up on pwm here.

We'll start by examining the schematic:


This shows how the bi-color LEDs of the ring of light (from now on ROL) is connected to the mcu (MS-VS55) and also how the center power led is connected.

The mcu outputs a 50Hz pwm that is then split up in two, an exact copy (PWM_LED1) and an inverted copy (PWM_LED2). This is the pwm that drives the led, it is its power source. PWM_LED1 drives D1 and D2 and PWM_LED2 drives D3 and D4. This pwm is ALLWAYS on, even when the XBOX 360 is in standby! The LEDs are then controlled (turned on/off) by controlling the ground.

Now comes the complicated part, they only use four inputs to control eight LEDs. The green and red leds are controlled in the exact same way so I'm just going to do this example on the green LEDs. So, the cathode (negative side) of D1 and D3, and D2 and D4 are connected together. The thing is these pairs (D1 and D3, D2 and D4) have the anode (positive side) connected to different pwms. One is connected to PWM1 and the other one is connected to PWM2. This way they will never get power supplied to them at the same time. So you can say that each LED gets a small time slot to control it's ground.

And a small picture of which pad is which since there has been some confusion about that:


I can add more info and some examples if needed, just send me an e-mail or a PM if you think it's unclear!

I think you forgot the pwm links I kinda want to read this.

Bookmarked.

damnit! I thought I checked it carefully. I'll fix it right now. Thanks for pointing it out!

Edit: Allright, as usuall I was fooled by my trace setup where the side with the leds is mirrored so that it will match up to the other side (vias and such). The picture is now fixed (I hope) and the links are fixed too. The links are just what I found on a quick google search so if anyone has any better just tell me and I'll add them!

/pablot

Added to Extras section in tutorials.

I was wondering something the other day about this...


when the 360 starts up, there is the pattern of the lights that it goes through, and than a little fade, and than it continues to serve its purpose showing which controllers are playing.


what part of the ROL (or maybe its something not on the ROL) is it that tells the 360 to use this pattern.

Would it be possible to reflash thta to make a different pattern / fade?? sorry if this is a dumb question, i haven't looked into this really at all yet.

I was thinking the same thing. It would be cool to change it.

I don't suppose you know on the Red Ring of Death daughterboard, which two points to solder to to add an extra power switch do you?

The power button seems to have four connectors, and it isn't obvious which are the ones needed to turn it on...

Momentarily shorting any of these points to Ground will duplicate the Power button.

I love you :-)

You have just saved me from probably breaking my 360! I was goign to start poking aroud and see what I found.

Anthony

I want to wire a switch to my board so I can move my power switch. Should I just wire one wire onto here and then find a ground point on the board? Or will that mess up. Help Please

You wire one side of your new power button to any of those spots, then the other side of it to any Ground spot, just like it was explained already.

Ok thank you. I was just making sure.

Just wondering if anyone has changed these LEDs before. I was thinking it would be cool to switch them so it always lights up red, but when there is an error it would light up green or blue or something. I am in the planning stages of my second system mod (first one was adding a fan header and 70mm case fan) and I'd like to change these LEDs. This topic has some pretty useful information that makes me think it would be pretty easy, but I'm pretty new to this kind of modification. Looking for any insight you guys can offer. Thanks a lot.