Post by: d00msday_jesus on April 04, 2007, 05:18:00 PM
It boots to MS dash without any problems at all.
The problem i'm having comes when i boot with the chip on. Theres no audio or video and it boots once, then turns off. Period. Its like the 3 boots at the beggining of a FRAG process, but stops everything after the one boot. Green PCB LED on the xbox.
Any ideas whats up?
Post by: AfterTheInsanity on April 04, 2007, 09:43:00 PM
What kind of chip, and what version motherboard to start off? It boots fine with the chip off, so that suggests that the traces are fine (otherwise it wouldnt boot at all), and it tries to boot with the chip on, so the D0 sounds fine, but I think your LPC points are off, if it doesnt load properly. v1.6 by any chance?
Post by: d00msday_jesus on April 05, 2007, 12:25:00 PM
Yeah, 1.6 with an x3 ce.
I noticed I somehow knocked one of those tiny ass caps off right above "R7R4" inbetween LAD0 and D0. I'm assuming this doesnt have anything to do with it because it boots to M$, but i could be wrong.
Post by: d00msday_jesus on April 05, 2007, 02:41:00 PM
Post by: AfterTheInsanity on April 05, 2007, 08:35:00 PM
See a problem here
You need to replace that resistor. You can either get an 0603 (I think) SMD version of it, and solder it back into place, or use a normal, 1/8w, 10k ohm resistor.Here's why you need that resistor (thanks nB):
QUOTE
The LPC (Low Pin Count) interface is specifically designed for peripheral expansion (much like the PCI bus, of which it is a subset). Now, many of you are likely used to the digital electronics concept of a TTL driver, the chip drives a voltage out to represent a "1" and pulls the signal to ground to represent a "0". While this method works fine when you have one chip talking to another, or even when you have one chip talking to many, it doesn't work so well when more than one chip may try talking at the same time.
What happens when you have one chip try to drive a 0 and another trying to drive a 1 at the same time? A lot of current flows across what is essentially a short circuit and one of the two chips dies (if you're lucky). How then do you put multiple devices on a bus and guarantee that you will never have this happen? Add a bunch of control circuitry and address lines. But what if you don't have the pins available to add the control lines? What if your little PIC micro can't drive the complex circuitry required? There is a simple solution: take away the ability of the chips to drive a "1".
So now things get interesting. When you make all your devices "open collector" you have essentially removed the transistor that puts out a voltage to drive a 1, but left in place the transistor that pulls the line to ground in order to output a 0. In this situation if more than one device wants to talk the data may get corrupted, but no damage will occur and you can simply ask the device to re-transmit. At this point you may be asking: yeah, but how do I transmit if I cant drive a 1? Those resistors are the answer.
Each of the LAD lines (as is the SDA line of the I2C bus) are capable of being connected to many devices, all of which have an open collector. The little resistors are 10K ohm pull-up resistors, that is to say they pull the lines voltage up when no chip on the bus is trying to pull it low. While this approach limits your total signal speed (33MHz on the LPC), it vastly reduces interface overhead and makes simple data busses easy to implement on small controllers.
The I2C bus is another example: The PIC, EEPROM, Video Encoder, and some of the LCDs all connect to the I2C bus, again through the same open collector principal.
The reason you can not simply replace a damaged resistor with a blob of solder (as I have seen some suggest), is that were you to do this, your pull-up would effectively be trying to drive as much current as it could into any chip trying to drive the bus to a 0, and in most conditions result in damage to any chips connected (mod, MCPx).
Update: Apologies for a factual error in the piece above. The LPC interface is not an open collector interface, it is a bi-directional interface requiring a turnaround where neither chip drives a signal, yet the bus must remain high. The specifics about open collector still applies, however. Thanks,
-nB
What happens when you have one chip try to drive a 0 and another trying to drive a 1 at the same time? A lot of current flows across what is essentially a short circuit and one of the two chips dies (if you're lucky). How then do you put multiple devices on a bus and guarantee that you will never have this happen? Add a bunch of control circuitry and address lines. But what if you don't have the pins available to add the control lines? What if your little PIC micro can't drive the complex circuitry required? There is a simple solution: take away the ability of the chips to drive a "1".
So now things get interesting. When you make all your devices "open collector" you have essentially removed the transistor that puts out a voltage to drive a 1, but left in place the transistor that pulls the line to ground in order to output a 0. In this situation if more than one device wants to talk the data may get corrupted, but no damage will occur and you can simply ask the device to re-transmit. At this point you may be asking: yeah, but how do I transmit if I cant drive a 1? Those resistors are the answer.
Each of the LAD lines (as is the SDA line of the I2C bus) are capable of being connected to many devices, all of which have an open collector. The little resistors are 10K ohm pull-up resistors, that is to say they pull the lines voltage up when no chip on the bus is trying to pull it low. While this approach limits your total signal speed (33MHz on the LPC), it vastly reduces interface overhead and makes simple data busses easy to implement on small controllers.
The I2C bus is another example: The PIC, EEPROM, Video Encoder, and some of the LCDs all connect to the I2C bus, again through the same open collector principal.
The reason you can not simply replace a damaged resistor with a blob of solder (as I have seen some suggest), is that were you to do this, your pull-up would effectively be trying to drive as much current as it could into any chip trying to drive the bus to a 0, and in most conditions result in damage to any chips connected (mod, MCPx).
Update: Apologies for a factual error in the piece above. The LPC interface is not an open collector interface, it is a bi-directional interface requiring a turnaround where neither chip drives a signal, yet the bus must remain high. The specifics about open collector still applies, however. Thanks,
-nB
Post by: d00msday_jesus on April 10, 2007, 01:56:00 PM
And just replacing the resistor will for sure solve this problem?
Post by: AfterTheInsanity on April 10, 2007, 06:06:00 PM
And if thats the only thing thats wrong, yes, replacing the resistor will fix it.
Post by: d00msday_jesus on April 11, 2007, 12:31:00 PM
Post by: AfterTheInsanity on April 11, 2007, 01:56:00 PM
If you dont want to desolder and resolder one of them, use a standard 1/8w 10k resistor, solder 30awg wire to each lead, and attach the wire to the pads (you can get normal resistors from Radioshack and the like).
Post by: d00msday_jesus on April 12, 2007, 01:14:00 AM
Post by: AfterTheInsanity on April 12, 2007, 07:15:00 AM
Post by: d00msday_jesus on April 13, 2007, 02:11:00 PM
i just want this to work. haha.
Post by: AfterTheInsanity on April 14, 2007, 07:58:00 AM
Post by: d00msday_jesus on April 14, 2007, 08:33:00 AM
Post by: AfterTheInsanity on April 14, 2007, 09:29:00 AM
Post by: d00msday_jesus on April 14, 2007, 09:38:00 AM
Post by: d00msday_jesus on April 14, 2007, 10:16:00 AM
I have NO idea how this slipped by me the countless times I went over it, but I somehow forgot to solder the LAD 3 point. Its all good and working now. FUCK I'M A MORON.
Post by: AfterTheInsanity on April 14, 2007, 12:03:00 PM
Post by: Moddage on April 15, 2007, 01:57:00 AM
Not to post jack, but you or anyone might find this inspirational, and if nothing else, interesting...
One thing that's changed GREATLY with me is my soldering... i used to be scared, and concerned with soldering my precious XBOX and other electronic stuff, I'll say it, i SUCKED at soldering tiny stuff, didnt have any equipment that was worth anything (all radioshack bought soldering irons), and didnt know any better to use flux...
Now i'm 150-200% better.... my very first job was at Bliley Technologies (local electronics manufacturer) and they put me through their solder technician training course (got paid for it too hehe).... anyway, long story short, I'm now IPC class 3 certified as far as soldering goes, and i bought myself a very nice station with 4 tips of various sizes...
The station i have now is a Hakko 936-12 ESD safe variable temperature station, and i have 4 various size tips, one is a 1.6mm chisel tip, and my smallest one is just over .007" at the very tip (pretty tiny right lol), i use some liquid flux that was left over from a second job placement, dont have much, but a little goes a ways... and when i need more i'll just order some online... its not like i own a business...
anyway, now i can solder basically anything you could possibly need to solder, and i've even had success with repairing traces by actually soldering to the trace itself (had no choice on a PS2, the trace dissappeared under a chip, one that happened to be the kind i can't remove and replace
)one thing i reccomend is to take a solder training course, even if you have experience with it, it cant hurt... i just got blessed enough to be in one for my job and get certified too.. aside from that i also got ESD certified, so i knnow how to properly handle electrostatic sensitive devices now...
anyway, just thought i'd share that info with y'all, and keep in mind i'm in no way trying to brag or boast, i'm sure i'm not the only one certified on these forums, and certainly not the only one who can solder... but as i said, if you have no experience, or even if you have some experience with soldering, its worth it to take a training course if you can find one, and if not, do as much homework about it on the internet as possible... and that goes for anyone reading this post.
Post by: d00msday_jesus on April 15, 2007, 05:54:00 PM