08/05/2012, 02:27 PM
Hi Wheelnut! Nice to read again from you! :-)
Thanks for your kind feedback. In the meanwhile I tested very much "material" together with the Touchpad and its USB capability in concern of the OTG mode. The first of all was the suggestion from here (was it you...?) with that solar powered USB hub from china. Then followed by other USB hubs with integrated power and not, then other power sources (battery and wall adapters), USB drives, USB sticks, USB mice with RF transceivers, USB Card readers (single and multi standard) and so on. And I made many cables on my own, especially USB Y cables, power cables and and and...
I think I have to start a new thread with all the stuff tested and how it behaves and so on. ;-)
But to your question:
During all the time with testing these several pieces of hardware, I found that the TP sometimes starts charging, sometimes not. Depending on the cables and the power source I used at that time. Given, that the external power source should not charge the TP but power the connected USB devices, I decided to make another interposer which simply "cuts" the 5V line into the TP. So the data lines are fed through and of course also GND. Done this way data communication is possible, but not feeding power to the TP.
In conjunction with all the tested hardware (USB hubs, USB devices and power sources) the only SAFE way of using all the USB sticks or memory cards with the several USB Card readers was with that interposer. Before I made that one, I randomly got communication problems with this card reader, that memory card or this day one setup worked, the other day not, sometimes the TP drains the external battery - sometimes not (which leads to that communication problems where current peaks while recognizing USB devices or transferring data from/to USB devices leads to randomly lost USB devices, etc.). Since I used that interposer, I never had any problems.
As a source for that interposers I also searched the net for a long time. The final solution is from china (of course) and intentionally made for charging Samsung's P1000. I just removed all the resistors inside and put in whatever resistors I needed. Actually I made one for charging the TP, then the cutted one for data transmissions only for the TP and also a third one for charging NOKIA mobile phones (Nokias need another resistor set inside than HP used for the TP to get full power charge).
Here you go: USB Power Adapter for Samsung P1000 - Free Shipping - DealExtreme
I also bought this one: USB Male to Female Data / Charging Switch Adapter Cable for Samsung Galaxy Tab P7500 + More - Black - Free Shipping - DealExtreme
and removed the PCB inside completely and engineered my own electronic to charge my R/C mini helicopters with any USB power supply (preferred the battery ones)... ;-)
YES, tell me crazy, but doing some PCBs for this or that job is not a big deal for me and I like professional results! I didn't yet take photos from that one but if you want, I can share them too. Not a big deal.
After all the testings I have done, one mobile battery for charging with one Y cable and an adapter and I can charge ANYTHING (my mobile phone, my wifes phone, the TP, the PSP, my heli, and and and...). Life is really fun when one can do his own electronis! :-)