Help On Wiki Schematics?

[GeminiDomino]

I'm looking through my parts bin for the bits to build my own semi-BOB. I'm slightly confused about one thing, though, and I'm usually pretty good about this sort of thing (for an amateur).

The Diode is a 1N914, right?

Also, has anyone shared the correct pinout for the JTAG yet? (The Wiki still says the one shown is wrong).

Beyond that, I just need to come up with a power supply. Looks like either a 9V battery (size) or 4 AAA cells (cheaper) should cut it, I think. If I'm wrong, I'd love to hear it.
UPDATE: *facepalms* Nevermind. That circuit is designed for AC... :rolleyes:

update: Oops, another question. If I were to wire the JTAG into a 9-pin serial header with the proper pinouts, it should then work with a standard RS232 cable instead of needing a special cable (since the pin-swapping will be done on the breadboard instead of in the wire), right?

 

[nubie]

UPDATE: *facepalms* Nevermind. That circuit is designed for AC... :rolleyes:

update: Oops, another question. If I were to wire the JTAG into a 9-pin serial header with the proper pinouts, it should then work with a standard RS232 cable instead of needing a special cable (since the pin-swapping will be done on the breadboard instead of in the wire), right?

Designed for AC? I don't think so, just protected by a diode.

Jtag is 20-pin.

RS-232 is a serial cable, Jtag interfaces are to the parrallel port.

If you mean you are putting in serial uart support, then yes of course you can wire that however you like.

Are you sure you should be doing this? Won't you fry your GP2X if this is your understanding of circuits?

What functionality are you looking for exactly?

 

[nubie]

Just a thought, why not ditch that plan for power and use one of these?

CyberPower USB hub

It uses 4 AAA batteries and is all ready to go

Just forget the wiring of that schematic for power and use this thing instead, it makes for a much cleaner mod.

 

[Squidge]

ARM JTAG standard is 20 pin, but 9 of those pins are ground, and several of the others are not really necessary, so you could place it into a 9-pin serial header and use a standard serial extension cable, but you'd still need to convert the other end from 9-pin to 25-way parallel, and considering the cable should be as short as possible, you really should just wire it directly.

 

[nubie]

ARM JTAG standard is 20 pin, but 9 of those pins are ground, and several of the others are not really necessary, so you could place it into a 9-pin serial header and use a standard serial extension cable, but you'd still need to convert the other end from 9-pin to 25-way parallel, and considering the cable should be as short as possible, you really should just wire it directly.

I am not saying that, I was pointing out that he was going to use a "standard rs-232" cable for jtag.

?? that is weird in my book. And scary, I call dibs if he fries his GP .

I do fully realize that Jtag can be put on smaller headers.

 

[Loubear]

Huh?!?!? Why did he have a vusb thing anyways if he's interested in jtag...? Oh btw, you don't need to have it filtered and all if you have a powered hub..right?

 

[nubie]

Huh?!?!? Why did he have a vusb thing anyways if he's interested in jtag...? Oh btw, you don't need to have it filtered and all if you have a powered hub..right?

Did you see the scope pattern on the wiki? (http://wiki.gp2x.org/wiki/Image:USB_Scope.png

Do you know what that means? It means that you need filtering, if you use a hub make sure it filters the signal, if not, put in this simple circuit.

2x 15k ohm resistors
2x 33 ohm resistors
2x 47picoFarad capacitors.

Just put em in, not that hard to get in the circuit somewhere, if your USB Hub includes a similar filtering circuit this one is unneccessary.

I do not have access to a scope anymore now that school is out for the summer, but if you do check your circuit, if it is a clean digital signal you are good.

 

[GeminiDomino]

Designed for AC? I don't think so, just protected by a diode.

Actually, it's the caps and lack of transformer that made me think A.C. But it occurs to me that at +6V it would have to be DC, probably from a wall-wart, which would have the transformer inside it.

Why the cap to ground, I'm curious?

ARM JTAG standard is 20 pin, but 9 of those pins are ground, and several of the others are not really necessary, so you could place it into a 9-pin serial header and use a standard serial extension cable, but you'd still need to convert the other end from 9-pin to 25-way parallel, and considering the cable should be as short as possible, you really should just wire it directly.

I am not saying that, I was pointing out that he was going to use a "standard rs-232" cable for jtag.

?? that is weird in my book. And scary, I call dibs if he fries his GP .

I do fully realize that Jtag can be put on smaller headers.

No, I didn't mean I was going to use a serial cable. That's just what I call the 9-pin connector out of habit. Since the Atari 2600 went away, it's the only place I see a 9-pin male anymore.

The issue being that it might be a bit more irritating to wire up the 9-to-25 pin parallel, but its been far more irritating trying to find the connectors for this crap.

 

[nubie]

Designed for AC? I don't think so, just protected by a diode.

Actually, it's the caps and lack of transformer that made me think A.C. But it occurs to me that at +6V it would have to be DC, probably from a wall-wart, which would have the transformer inside it.

Why the cap to ground, I'm curious?

I am not sure why that extra cap, maybe just protection for spikes to the 7805, or possibly just to make the voltage signal as clean as possible.

No, I didn't mean I was going to use a serial cable. That's just what I call the 9-pin connector out of habit. Since the Atari 2600 went away, it's the only place I see a 9-pin male anymore.

The issue being that it might be a bit more irritating to wire up the 9-to-25 pin parallel, but its been far more irritating trying to find the connectors for this crap.

You forgot the Genesis , but seriously you can't source a connector? Which one? For Jtag since I am assuming you will be making your own Jtag to Parrallel cable you can use a standard set of jumper pins, whatever configuration makes you happy. To get the Female Parallel connector I use RS-232 D-25 connectors from old 486 PC's or ISA cards. I have tons of them. The Jtag doesn't have to look all that nice and can be under a panel where it doesn't show, anyone who really needs it will understand .

Did you see that battery-powered USB hub? Four 850mAh AAA batteries should do the trick . I would get one of those if I wanted portable, what are you planning on?

 

[Loubear]

Huh?!?!? Why did he have a vusb thing anyways if he's interested in jtag...? Oh btw, you don't need to have it filtered and all if you have a powered hub..right?

Did you see the scope pattern on the wiki? (http://wiki.gp2x.org/wiki/Image:USB_Scope.png

Do you know what that means? It means that you need filtering, if you use a hub make sure it filters the signal, if not, put in this simple circuit.

2x 15k ohm resistors
2x 33 ohm resistors
2x 47picoFarad capacitors.

Just put em in, not that hard to get in the circuit somewhere, if your USB Hub includes a similar filtering circuit this one is unneccessary.

I do not have access to a scope anymore now that school is out for the summer, but if you do check your circuit, if it is a clean digital signal you are good.

Nonono! That wasn't what I was talking about, i was talking about the voltage part, not the data wires.

 

[GeminiDomino]

Actually, it's the caps and lack of transformer that made me think A.C. But it occurs to me that at +6V it would have to be DC, probably from a wall-wart, which would have the transformer inside it.

Why the cap to ground, I'm curious?

I am not sure why that extra cap, maybe just protection for spikes to the 7805, or possibly just to make the voltage signal as clean as possible.

I thought it might be something like that. I'm still trying to figure out the theory of this stuff (any monkey with a steady hand can put it together. I want to understand why, so I appreciate the answer. )

No, I didn't mean I was going to use a serial cable. That's just what I call the 9-pin connector out of habit. Since the Atari 2600 went away, it's the only place I see a 9-pin male anymore.

The issue being that it might be a bit more irritating to wire up the 9-to-25 pin parallel, but its been far more irritating trying to find the connectors for this crap.

You forgot the Genesis , but seriously you can't source a connector? Which one? For Jtag since I am assuming you will be making your own Jtag to Parrallel cable you can use a standard set of jumper pins, whatever configuration makes you happy. To get the Female Parallel connector I use RS-232 D-25 connectors from old 486 PC's or ISA cards. I have tons of them. The Jtag doesn't have to look all that nice and can be under a panel where it doesn't show, anyone who really needs it will understand .

You're right, I did.

My main idea was a more modular design, so instead of wiring in cables directly, and having to worry about them working loose, I was liking the idea of mounting headers and having the cables themselves removable. Just to make things easier to work on and test (it's easier to track a pin on a header than the tip of a 28AWG wire. )

The real PITA though is that Rat Shack doesn't have jack (pun intended) as far as headers and connectors, and the web sites seem to only have one of what I need, so I'd be looking at ordering from 5 places. You may have a point, though. I think I've still got an ancient ISA super-serial card in my garage... that's a start.

The real trick is going to be finding and wiring up the EXT connector. I think I may just have to sacrifice my TV out. I can't seem to find a 20-pin header (somethng like a mini-IDE mounting) so was thinking of using jumper headers and a bunch of single and double-pin wires like the front panels of Motherboards use these days. Easy to wire, but the resulting mess will turn into quite the clusterfsck.

Did you see that battery-powered USB hub? Four 850mAh AAA batteries should do the trick . I would get one of those if I wanted portable, what are you planning on?

Depending on how tight I can get the components (breadboard prototyping is showing some promise) I was thinking I might be able to hack up some way to have it "latch onto" the back of the unit (like most of the GBA accessories on the original, except hanging behind instead of in front). Barring that, portability becomes a non-issue, since I'm going to be using it with my portable hard drive mostly, which requires 120V plugin anyway.