Have a look at the STF201 docs: http://www.semtech.com/pc/downloadDocument.do?id=139 particularily figure 4. Pin 1 is used to clamp transients on the 5V line. I believe the actual USB data lines are 3.3V differential signals.
Newark Electronics sells the Semtech STF201-22 for around $2 ea ($25 min order). This is a very small surface mount chip and you need specialized soldering equipment and a good magnifying glass to solder to it.
I just had a GREAT idea :approve: - Instead of building the interface into the Axim, purchase a powered USB hub, wire it into an X50/X51 sync connector and let it be a dedicated interface - with several USB ports! Oh - I am so proud of myself
Of course, we'll still need to place a couple of transient diodes inside the case - just not a whole interface circuit.
Good! :approve:
Once having the hack working sure it could have several implementation ways.
But not all people will be able to do so delicate work :rolling:
Good! :approve:
Once having the hack working sure it could have several implementation ways.
But not all people will be able to do so delicate work :rolling:
Yes, I know. At this time, both points are on the top of the PCB and only one is on the bottom. I hope I can find a second point on the bottom, close to the sync connector otherwise we will have to bring at least one wire around from the top to the bottom - or add a mini USB connector through a cutout in the case (yuck ). The problem with USB data lines is that they must be the same length or you end up with skew and you get lousy data throughput with lots of errors.
Yes, I know. At this time, both points are on the top of the PCB and only one is on the bottom. I hope I can find a second point on the bottom, close to the sync connector otherwise we will have to bring at least one wire around from the top to the bottom - or add a mini USB connector through a cutout in the case (yuck ). The problem with USB data lines is that they must be the same length or you end up with skew and you get lousy data throughput with lots of errors.
Yes, I already dealt with this problem, that is the reason I had to build a second version of Aximizer: problems with USB hub. Those problems become critical, almost impossible to handle, when dealing with USB 2.0 signals, fortunately this is not the case (or I have to say: unfortunately )
For same reason it does not make much sense having only POS signal at the bottom area, it is supposed signal pair should go together for noise differential filtering.
If we have both lines at the bottom it should simplify the work a lot.
STF201-22 is same size like that one shown in the middle of your latest picture. An IC like that could be placed up side down at near clear area, stuck with epoxy and wired with that very thin wire used to fix broken board lines or when lines are cut during troubleshooting. Distance seems short enough for 1.1 signals, but still twisting lines will be a good prevention.
There is one problem about the USBH-P location, see the picture, white line shows where battery room starts. Some sort of very flat wire should be used.
I prefer the idea of having driver IC inside PDA if possible but, as I said at previous post, knowing where the lines are, hacking it can have several implementations :approve:
good work bigbop. i know i'm excited to see how this all works out. certainly, i'd be willing to wire it to an external root hub... i'm definately looking for ways to link the direct lines to an outside source... i mean, if you really think about it, you're going to need to have the usb connector, connect using an axim sync connector, where you will have the space to impliment any IC's you'll need to make it 100%... so looking into the unit to put ics, though, as accomplishing as that may seem... doesn't seem practical at all... considering you'll need a custom connector to use the usb anyways.
There is one problem about the USBH-P location, see the picture, white line shows where battery room starts. Some sort of very flat wire should be used.
EEK! you've got the wires shifted down one pin too many. The pins with no connection are the ones on either side of the middle gap.
I think I'm going to have to scrape off the green soldermask on the vias to see if one is connected to the USBH-N pin.
Sorry about my english, but I do not undestand what you mean.
Do you mean USBH-N could be "here" (see picture)?
No. These types of circuit boards use blind vias. A via is essentially a feedthrough from one layer to another. With the older 2-sided PCBs, they were simple feedthroughs from the top to the bottom.
However, that changed on todays multi-layer PCBs. If the Axim uses a 6 or 8 layer board, you will have the top and bottom layers plus a 5v and gnd layer. You will also have the conductor layers which will be in-between the other layers. In order to get connections from one internal layer to another, vias are used. They become blind vias when they are only in the inner layers and don't appear on the top or bottom of the PCB.
If you look really close at the top of the X50/X51 PCB, you will see what look like small pads just under the top surface. Those are on the 2nd layer of the board and you cannot connect to them.
Unfortunately, since I don't think the USBH-N pad is on the bottom, you cannot just scrape away some copper and expect the blind via to be there (but it would be nice though).
What I meant in my previous post was that I would scrape off the green soldermask from a number of vias that are exposed on the bottom of the PCB and see if any are connected to USBH-N (you never know).
I purchased a cheap $6 USB 2 port self-powered hub and pulled it apart.
The hub has the name GoldX on the top and the model number is GXMU-102 (http://www.jditech.com/showproduct.asp?pid=GXMU-102)
You can also use the GXMU-104 4 port hub as it's the same unit inside - see below.
The AT43301 is a 4 port USB hub controller chip with everything integrated into it including overcurrent detection (500mA per port) and transient protection. There are misc resistors and caps on the board. As I stated in post 180, this is probably your best bet on bringing out the host ports since you're going to need a powered module anyways to power your USB toys. I've seen this unit as cheap as 99 cents on eBay (+S&H of course) but any local computer store should sell it for what I paid. There are two screws under the serial number label.
I am going to wire this hub up so that I supply 5v to it and it supplies 5v to my X50v. The GXMU-201 hub's circuit board is already set up to take a barrel connector for an external PS and 2 more USB sockets (for a total of 4). Page 20 of the spec sheet has the basic schematic. I will be connecting JP1 to the Axim.
I'm going to connect to the USB host lines in the CPU shield area using twisted wires (for noise immunity) and see if I can wrap them around the bottom edge of the PCB beside the sync connector.
I probably won't have this done until Wednesday or Thursday.
Thank you for the explanation.
In that case better to make connections to the place where D+/D- are together :approve:
So you are not going to use a STF201-22 IC at all, right?
Thank you for the explanation.
In that case better to make connections to the place where D+/D- are together :approve:
So you are not going to use a STF201-22 IC at all, right?
Right - I will be sticking a couple of zener diodes on the USB lines. I need to check the voltage specs to see what zener voltage I'll need.
I'm not worried about protecting them too much as they will only be connected through the sync connector to the USB hub interface which has its own protection.
Right - I will be sticking a couple of zener diodes on the USB lines. I need to check the voltage specs to see what zener voltage I'll need.
I'm not worried about protecting them too much as they will only be connected through the sync connector to the USB hub interface which has its own protection.
I have similar setup with Aximizer :)
Arrrggggg! I need my tools!!! :iconbangh
Thank you for the explanation.
In that case better to make connections to the place where D+/D- are together :approve:
So you are not going to use a STF201-22 IC at all, right?
By the way, the STF201 costs more than the compete 2 port hub with case (when you add in shipping costs). Keep it simple inside the Axim's case and place the active stuff externally.
By the way, the STF201 costs more than the compete 2 port hub with case (when you add in shipping costs). Keep it simple inside the Axim's case and place the active stuff externally.
Bigbop, will any usb hub do? or we have to get your GoldX model GXMU-102?
I have one 4-port usb-hub lying around, it has a Genesys Logic chip GL650USB.
All I need is to connect the USB-P & USB-N, gnd. Then provide a external 5v pwr to hub??? Please do let us know any finer details once we can start get the ball rolling.
Bigbop and others, really a BiG thanks for all the hardwork and sharing.
I believe alot of us is reading this thread, although not contributing (we don't want mess it up here!)
Bigbop, will any usb hub do? or we have to get your GoldX model GXMU-102?
I have one 4-port usb-hub lying around, it has a Genesys Logic chip GL650USB.
All I need is to connect the USB-P & USB-N, gnd. Then provide a external 5v pwr to hub??? Please do let us know any finer details once we can start get the ball rolling.
Bigbop and others, really a BiG thanks for all the hardwork and sharing.
I believe alot of us is reading this thread, although not contributing (we don't want mess it up here!)
Gump, i think you'll need an extra circuit, because i don't think the output from the circuits that we're trying to take the leads from on the 51v are *final* USB Host config. so there's a small transition circuit, then into your host lines on the hub (bigbop/afarre, feel free to correct me if i misunderstand)... other than that, you'll just need to have it be capable of external power... make the right connections, and you're set. :D
though, i'm still a bit foggy on what the "right" connections are... so i'm waiting for afarre or bigbop to complete a working model of the hardware, then we can get the software & do testing... when that's all good, i'll consider voiding my warranty... until then, i'm gonna stick with my 3yr advanced exchange :P as for everyone else, if you don't have a warranty to worry about, as soon as we have working models, go a head, give'er a go.:approve:
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). The problem with USB data lines is that they must be the same length or you end up with skew and you get lousy data throughput with lots of errors.
