[orcinus]

I've noticed that when i pull out the RAM from my TiBook and turn it on, the white sleep LED behaves differently than usual - in this case it turns on while the machine is running and blinks twice every x seconds to indicate that something's wrong. That would, IMHO, imply that the circuit driving the LED isn't just a dumb pulse width modulated fade in/out thingy that activates when the machine is in sleep, but rather something completely controlled by firmware (not necesserily OF part - perhaps something in the PMU?).

Now the question that's been bothering me is this: would it be possible to control the LED via software? If it would, it'd make for a rather cool software mod - you could, for example, set it to switch on or blink when a new mail comes in so you could tell it from across the room even with the screen backlight blanked out, or it could be set to indicate CPU activity, act as a HDD activity light or any number of things...

If it is possible to control it (by some kind of low level direct calls), it'd probably require writing a new kext. Kernel extensions, drivers and stuff like that are, unfortunately, way beyond my beginner's coding skills. Any experienced coders out there with an idea?

Orcinus

[SSharon]

that would be cool to see, definately an off switch also. when my MDD is sleeping that little light actually lights up the room when it gets bright. someone in the software forum would probably know more about it.

[cdhostage]

Eeeeeeenteresting. It used to be Macs reported physical malfunctions (if they were able to start up at all) with varying beeps at startup.

I know nothing about this.

[orcinus]

aHA!

I've been snooping around (via Google) a bit and, well, it seems LinuxPPC (IDE driver, to be exact) got patched relatively recently with an option to use sleep LED as an HDD activity light on G4 pbooks!!!

SO IT IS possible!

Orcinus

[gbarill]

but does anybody know how to take advantage of this in mac os x?

[deej5871]

This sounds like a pretty interesting idea. Isn't there anyone out there that knows how to do something like this?

[rag on a muffin]

this is EXACLY why i came to the mods section!! please keep posting!! i always wanted to do that with the light.

[rag on a muffin]

*bump* any ideas? anyone at all?

[digital_dreamer]

It's not as easy as one might think. Here is the circuit:

http://idisk.mac.com/digital_dreamer...Controller.jpg
Please review and obey the inline image rules, posted at the top of every forum. -- tooki

See my post at Ars Technica for more details.
The circuit uses a Philips 87LPC767, a low-power, 20-pin microcontroller with 4kB of EPROM. This is a extremely flexible, yet low-cost SMC. It even includes a Idle and Power Down mode with wakeup. The chip can also drive LEDs directly (up to 20mA) without the need for a external buffer/driver.

Controlling this circuit is well beyond most DIY'ers. Since this chip has a EPROM with the program already burnt-in, it useless for modifications. (You must buy it new and burn the program in. And, it's good for only one burn.)

Here's what I've done with my DIY dual G4: Using the circuit I designed below, I have a multi-colored LED (Laser LED) that pulses when the system is in deep sleep.

http://idisk.mac.com/digital_dreamer...%20Circuit.jpg


Here is the actual circuit hot-glued on the inside of the front panel:

http://idisk.mac.com/digital_dreamer...anelWiring.jpg

The sleep circuits requires a tap on one of the voltage regulators. The goal is to find terminal/connection that supplies +5 during sleep. Tricky and dangerous (to motherboard, not you) if you are not careful with a meter.

Here is where I soldered the sleep connection for +5 during sleep on a Gigabit Ethernet board:

http://idisk.mac.com/digital_dreamer...ep5VoltTap.jpg

I will not be held liable/responsible for anything you do as a result of this post.

regards,
MAJ

[deej5871]

Wow, thanks for the info. I didn't realize it was that complex since previous posts made it seem that all that was need was a firmware mod. Looks like my light will remain how it is...

[rag on a muffin]

wow. i didnt think that either, because of the firmware hack orcinus said too.

[Link]

Judging by that chip setup there.. it DOES use pulse width modulation to do the "pulse" but it's controlled by a simple 1-100 sort of control. That's spiffy but not surprising.

If the controller can be overridden to use it as an HD status light I'm sure there's a way to disable it.

[digital_dreamer]

Originally posted by Link:
Judging by that chip setup there.. it DOES use pulse width modulation to do the "pulse" but it's controlled by a simple 1-100 sort of control. That's spiffy but not surprising.

If the controller can be overridden to use it as an HD status light I'm sure there's a way to disable it.

Correct, the LED's intensity is varied via PWM, not analog.
It does seem that Open Firmware contains some basic commands that are sent via serial link to controller (i.e. no RAM indicator).

I suppose one could cut the traces on the LED and wire it to the HD activity connection. That would be pretty simple.

BTW, where is this LinuxPPC HD light mod orcinus is referring to? Linky?

regards,
MAJ

[n9yty]

Originally posted by digital_dreamer:
BTW, where is this LinuxPPC HD light mod orcinus is referring to? Linky?

I don't know if it's the same one, but this link has a huge patch file, inside of which (starting at line 7023) is the code:

http://www.flamingspork.com/linux/ke...-stew1-xfs.bz2

[rag on a muffin]

so whats the deal? is someone gunna try it? that would be really cool.