[Nexus 7] Adding internal USB for other devices (HUB,microSD,FM,flash-storage,etc...)

The project-Adding internal USB for other devices (HUB,micro SD,FM,flash-storage,etc...).

We should have a few deferent options to connect USB internally. This thread should cover them all.

I really want to find a easy solderless method(plug/clips) I have a few ideas but would need to find the female and male connectors for the front camera or maybe soundboard connectors.
or
maybe disconnect the micro USB from the ribbon and run it up to the hub then back to the micro USB connector from the HUB that's one reason for the hub, so we can add a micro SD, a rear camera and the last port (HUB only has 3 ports active, it might be possible to find a different HUB that has 4 ports but this one only had 3) for ether some more flash storage or to hook up the solderless mod to mother board.

We can use the micro USB connection at bottom of the mother board a couple different ways. We could use both the data and power from the connector. We could also just use the data +/- from the micro USB connector and use the power from a different power source like the 7.4V from the battery and drop it down to 5V but none of the wires are 7.4v there is two running at 3.7v, if we could find the 7.4v on the board or a connector somewhere this could be done

Some pics


http://s10.postimage.org/6zg4euc21/N7_cable.jpg

Camping for a few days with the family, then back at it.

So I soldered in a switch to id pin and ground pin of micro usb all was good, charged when powered on and switch off, charged when power was off switch on or off. Now I soldered microsd card reader power and data lines to the microUSB connector them ran the ground for card reader up to switch, it works fine for mounting sdcard, but it won't charge when N7 is booted up. It does charge still when not booted up. Maybe I should have ran the ground for the card reader to microUSB port too. But at least it works and is all internal.

I've been doing a lot of digging into the USB OTG spec, and I think I have a clearer picture now why we might run into problems even if we find some alternative +5V line. I drew up some high-level schematics that show the four operating modes of the stock Nexus, and then shows what happens when you simply tie a peripheral into the usb traces while still permitting external connections through the usb receptacle.

Basically, if you tie the internal reader to the GND, D+, D-, and VBUS lines behind the receptacle, and short the ID pin to ground, you don't have any problems. You've just replicated the functionality of the OTG cable. The problem arises when you try to attach something to the external receptacle, while the internal reader is still soldered in:

1. When you plug a high-capacity charger (e.g. the stock charger) into the receptacle, the charger shorts the data lines together. The internal card can no longer be read. Moreover, asserting VBUS from an external source while shorting ID to ground is against USB spec. I'm concerned that the Nexus's onboard USB transciever will go into a safe state that drops all data communication even after the charger is removed. That might explain why some folks needed to reboot their nexus after trying to charge and read at the same time.

2. When you plug a PC (or any A-device) into the receptacle, the data lines get shared by both the PC and the internal reader. The Nexus tries to be host (A-device) which conflicts with the PC's host status. Not sure if the PC or the nexus can read the card. Not sure if the PC can read the nexus drive. Not sure if the nexus will charge.

3. When you plug an OTG cable into the receptacle, the nexus acts as host (fine). But the data lines are now shared by both the internal and external peripherals. Not sure if the nexus can read the internal or the external peripherals.