There are five digital signals that have pullup
resistors connected. CMD and the four data lines.

Since he’s saying tha card is idle if the analog
voltage is greater than a magic value, I’m
guessing he’s monitoring one of these five lines,
and when it starts toggling that he sometimes
detects a “low” on a line and lights up the LED.

It seems like just hooking the CMD line up to a
digital input on the PIC and turning on the LED
for 1 second or so every time it goes low would
also do it, but you’d need to make sure the
voltage at CMD went high enough to show as a “1″
on the PIC.

Without a schematic it’s pretty much guessing for
me, so I expect to be wrong about some of this.
(I didn’t create a login on that website to be
able to look at the photos, so there might be
some useful information in those also.)

At first I thought it was overkill to use a microcontroller for this when a single transistor or monostable timer would do.

But then at £1.50 for a PICAXE 08, why not?

Good job anyhow.

What do the images show that are linked in the post?

Sorry about that. I was not aware that you had to be a member of wiihacks.com to view anything on the site.

So I uploaded my pics to my FB page. Here are some of the pics.
http://bit.ly/ecm1dB
http://bit.ly/ihom7t
http://bit.ly/hTEQ4k
http://bit.ly/e64E4Z

And here is the initial code that I used, although I have changed it up a bit to be able to detect slight voltage changes, but I lost the file that had the newer code in it, so here is the first bit of code that I did.

start:
setfreq m4
low 1                

main:
readadc 4,b1
if b1 > 210 then
        low 1
end if
if b1 < 210 then
        high 1
pause 50
end if
goto main

Basically what I have going on here is that pin 4 of the 08M reads the voltage of the SD cards pin 7. Pin 1 of the 08M controls the LED. I was able to find a constant 5v output on the wii’s motherboard and used that to power the 08M.

If people still insist on a schematic then I can do one up, but I’m sure it will look cheesy.

I tried using a transistor at first, but what would happen if that the LED was always on when the SD card was idle, and the LED would just go dim where there was data activity. Plus at times the transistor was taking up too much voltage from the SD card’s pin 7 and would cause there to be no data written to the SD card and it would fail. I used the 08M to get around these issues so I could slow down the blink rate and so too much voltage wasn’t being taken away from the SD card’s pin 7.

I know I don’t NEED a micro-controller to monitor voltage, but this was part of the fun of having an afternoon project. I did the hack for fun, not for efficiency.

did you try a different type of transistor (NPN vs. PNP).

@DeadlyFoez.
Then an Op-amp, a comparator even a 555 will do. They have much high input impedance.
And if the voltage is compatible to a logic level, most logic device can handle it.

gdogg, i know. he said it was always on when the SD was not being accessed.

“the LED was always on when the SD card was idle,”

@st2000
SD cards use the SPI clock as the primary clock. If you don’t have the SPI clock running, the SD card will be frozen in time, unaware that anything is going on, and won’t be doing anything on their own.

I know that in pretty much all of my applications I simply clock when I input a command, and the spec demands that I send an empty clock period in order to give the SD card enough “time” to process, because it can’t run unless there are clock pulses.

This is (from what I recall) pretty well laid out in the spec. So in most uC cases, you can be certain that if you’re not running a command, the SD card is safe to yank.

@seer, I thought about using a 555 timer since I have one kicking around. I don’t have any op-amps nor have I ever played with one to know how to correctly use it.

But with a 555 I would have to add in more components like capacitors and resistors and I did not want to have to add in more than needed. I really wanted to keep it simple and I succeeded in that.

I remember my updated code that works better.

start:
setfreq m4
low 1
readadc 4,b1

main:
readadc 4,b2

if b1 > b2 then
	let b3 = b1 - b2
else
	let b3 = b2 - b1
end if

if b3 > 7 then
	toggle 1
else
	low 1
end if

let b1 = b2
pause 50
goto main

Basically what is happening is that the micro controller and checking the voltage of pin 1 (variable b1), then it goes and and checks it again (variable b2). It then compares those 2 variables. If the value is greater than 7 then it knows that the SD card is not idle and it will proceed to toggle the output of pin 4 (for the LED).

I had to do it this way because many times the wii will read or write data to the SD card via serial connection with data only being transfered via pin 7 of the SD card. But I have noticed that many time of trying to write data to the sd card that is all bits of 1, the 08M would see that as the card being idle because it was on high for a longer period to the point that the 08M would get a reading that was higher than 210.

In the end, this worked out pretty sweet for someone who doesn’t have a whole boat load of electrical skills.

@EE, if I knew what those were then I probably would have thought of it as an idea. Quite honestly, I don’t have really any skills in this field at all. I’m great with soldering and thats about it. I was lucky enough to pull together a few things that I had kicking around and knowing just enough about it to be able to make it happen.

The only thing I really had going for me is that I used program in QBasic a lot as a kid.

So I decided to try and see if I could add in a NAND activity LED to my wii. For this I used my PICAXE 08M micro controller to to read the CE pin of the NAND flash chip to determine if there is activity. When there is any NAND activity, the CE pin become low (0 volts), but when idle the CE pin floats at around 3.5 volts.

The SD card activity is determined by pin 7 of the SD card that the PICAXE reads. When idle, pin 7 floats at a voltage range, but when there is activity then the voltage will bounce all around.

I changed the way that I have it now it before. Now the blue SD card activity LED is placed above the SD card slot and the red NAND activity LED is to the left of the SD card slot.

I also added in a headphone jack to the right of the SD card slot. This headphone jack is used to reprogram the micro controller.

[img]http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs736.ash1/162958_172245846148049_100000879040713_328375_5028548_n.jpg[/img]

[img]http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1384.snc4/163674_172245869481380_100000879040713_328376_3443203_n.jpg[/img]

The video below demos the activity of the NAND and SD card activity LED’s.

start:
setfreq m8                        ;Make sure the frequency is set to 8 Mhz
low 0 , 1                         ;Make sure pins 0 and 1 are low
main:
readadc10 4,w0                    ;Read pin 7 of the SD card.
if w0 < 604 or w0 > 620 then      ;values between 604 and 620 are when the SD card is idle.
    toggle 0                      ;If there is activity then toggle pin 0 (the blue LED)
else
    low 0                         ;If there was no activity then make sure pin 0 is low
end if
readadc 2, b2                     ;read the CE pin of the NAND flash
if b2 = 0 then                    ;A value of 0 means there is NAND activity
    toggle 1                      ;If there is activity then toggle pin 1 (the red LED)
else
    low 1                         ;If there was no activity then make sure pin 1 is low
endif
goto main                         ;Go to the main: label to loop the code.

[b][size="3"]Future additions:[/size][/b]
Wifi activity indicator
CPU temp monitoring
Fan speed controller
Backlit LCD displaying various things.
NAND reprogramming via PICAXE and SD card (No infectus needed)
Wiimotes that will explode if my wife has been playing games and not doing dishes :D