[Nexus 7] Adding internal USB for other devices (HUB,microSD,FM,flash-storage,etc...)
- Thread starter iAppleDev
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EBAY'D 6x 8gb MAINBOARDS FOR TESTING. Lets make this work here to apply towards n7 v2
So this thread and all related to it seem to have died which I don't get because the roadblock behind progress was charging in otg mode which fauxs kernel solves. but I'm determined to find internal otg solutions to what i feel are serious set backs to small form factor tablets that just can't be solved with(buy a pricier tablet). Even at 600 bucks I can't find a 7-8 inch that meets my peripheral needs and I'm also interested honing my soldering skills ass well as expanding my understanding of micro electronics. So please no "waste of money" nonsense as everything learned here can be applied to future USB otg capable devices. Namely the upcoming nexus 7(2) but as parts will be costly and rare to begin with I have a number of 8gb motherboards I've purchased to offer to the gods of science and burnt fingertips before applying to future tablets till wireless finally prevails or we find 6usb port tablets mass marketed. Im split between continuing this thread that seems most elaborate of the many Ive read.. Im not interested in pipedream smt memory replacemenf or opposed to a physical switch. Im talking about tapping into the USB circuitry to allow Simultaneously charging and use of a flashdrive/hub and having g the option for wired PC connection by turning otg off.
In short I will get new phones/tablets but I will not be starting any other projects big or small until I've made a working internal hub solution and guide to achieving it(for those who buy devices to tinker with more so than use not your average Joe looking to upgrade.
So far I've got another micro USB port connected directly behind the first pointing in as my internal tap. I want to wire a switch that grounds the ID pin and connects + - D lines to the nexus to engage the hub. The other position would place the tablet behind the hub so it would list along with all the other added devices when connected to PC. This might take cutting traces I'm guessing... And is where I'm gonna need some help figuring out. If this turns out impossible then disabling otg all together so the nexus can interface with PC would be my back up solution. When all is said and done I plan to comprehensively detail the proceedure so others may try.
So this thread and all related to it seem to have died which I don't get because the roadblock behind progress was charging in otg mode which fauxs kernel solves. but I'm determined to find internal otg solutions to what i feel are serious set backs to small form factor tablets that just can't be solved with(buy a pricier tablet). Even at 600 bucks I can't find a 7-8 inch that meets my peripheral needs and I'm also interested honing my soldering skills ass well as expanding my understanding of micro electronics. So please no "waste of money" nonsense as everything learned here can be applied to future USB otg capable devices. Namely the upcoming nexus 7(2) but as parts will be costly and rare to begin with I have a number of 8gb motherboards I've purchased to offer to the gods of science and burnt fingertips before applying to future tablets till wireless finally prevails or we find 6usb port tablets mass marketed. Im split between continuing this thread that seems most elaborate of the many Ive read.. Im not interested in pipedream smt memory replacemenf or opposed to a physical switch. Im talking about tapping into the USB circuitry to allow Simultaneously charging and use of a flashdrive/hub and having g the option for wired PC connection by turning otg off.
In short I will get new phones/tablets but I will not be starting any other projects big or small until I've made a working internal hub solution and guide to achieving it(for those who buy devices to tinker with more so than use not your average Joe looking to upgrade.
So far I've got another micro USB port connected directly behind the first pointing in as my internal tap. I want to wire a switch that grounds the ID pin and connects + - D lines to the nexus to engage the hub. The other position would place the tablet behind the hub so it would list along with all the other added devices when connected to PC. This might take cutting traces I'm guessing... And is where I'm gonna need some help figuring out. If this turns out impossible then disabling otg all together so the nexus can interface with PC would be my back up solution. When all is said and done I plan to comprehensively detail the proceedure so others may try.
Renate
Recognized Contributor / Inactive Recognized Dev
Here's a couple of hints:
When trying to get this thing to work, you can just prototype all your stuff externally.
You can have a micro USB plug into the Nexus and a micro USB socket which will stand in for the Nexus socket until you migrate to the finished version.
To make this real, you're going to have to have a total of 3 USB DPST switches, that could be 1.5 USB DPDT switches.
If you can do without external USB devices, that's 2 USB DPST or 1 USB DPDT.
CD4000 series is not going to work. They have much too high an on resistance.
Real USB muxes like the TS3USB30 have much lower resistances.
The only way that I can see this project being a real win is if somebody has some PCB's made up.
You'd need at least one mux, optionally a hub, an MMC controller and a micro SD socket.
You'd also need some discrete stuff for power control and ID pin.
You'd need some way to switch direction of the USB flow.
You might snarf a GPIO pin somewhere off the motherboard.
You could add a physical switch.
You could have it that you need to insert a dummy plug in to pull down the ID pin.
When you are all done, the Nexus as a peripheral on a desktop will still not be able
to access the additional SD card, unless you add another multiplexer.
Even if you made this all up, it might be difficult to have some users here break the connection to the stock USB connector and wire up both sides.
No, I don't have a Nexus 7, which is why I am a bit aloof from all this.
I do use host mode on my Nook Simple Touch and I do charge while doing that.
When trying to get this thing to work, you can just prototype all your stuff externally.
You can have a micro USB plug into the Nexus and a micro USB socket which will stand in for the Nexus socket until you migrate to the finished version.
To make this real, you're going to have to have a total of 3 USB DPST switches, that could be 1.5 USB DPDT switches.
If you can do without external USB devices, that's 2 USB DPST or 1 USB DPDT.
CD4000 series is not going to work. They have much too high an on resistance.
Real USB muxes like the TS3USB30 have much lower resistances.
The only way that I can see this project being a real win is if somebody has some PCB's made up.
You'd need at least one mux, optionally a hub, an MMC controller and a micro SD socket.
You'd also need some discrete stuff for power control and ID pin.
You'd need some way to switch direction of the USB flow.
You might snarf a GPIO pin somewhere off the motherboard.
You could add a physical switch.
You could have it that you need to insert a dummy plug in to pull down the ID pin.
When you are all done, the Nexus as a peripheral on a desktop will still not be able
to access the additional SD card, unless you add another multiplexer.
Even if you made this all up, it might be difficult to have some users here break the connection to the stock USB connector and wire up both sides.
No, I don't have a Nexus 7, which is why I am a bit aloof from all this.
I do use host mode on my Nook Simple Touch and I do charge while doing that.
Renate
Recognized Contributor / Inactive Recognized Dev
A neat way to do this would be with a monolithic "baseball" switch.
(A baseball switch rotates 90 degrees to select the other pattern.)
That's basically a four port switch that would be a DPDT for single-ended signals or 4PDT for differential signals.
Yes, you can create an equivalent with two 2-1 USB multiplexers,
but the PC layout and performance would be better monolithic.
Unfortunately, as far as I know, nobody makes such a device.
(A baseball switch rotates 90 degrees to select the other pattern.)
That's basically a four port switch that would be a DPDT for single-ended signals or 4PDT for differential signals.
Yes, you can create an equivalent with two 2-1 USB multiplexers,
but the PC layout and performance would be better monolithic.
Unfortunately, as far as I know, nobody makes such a device.
Attachments
To simplify things the switch is only going to trigger otg on and off. The original usb port at this point will be useable for charging with the correct kernel and communicating with the nexus only when disengaged with zero access to the extra devices.. A second external port has been routed which goes directly to the hub. When connected to a pc it will power the hub and allow the device to see the usb devices and nexus so long as the nexus is otg off. This all works externally already. basically i have a 4 port w/microsd usb hub with all the ports removed. One of them is salvaged and just extended to outside the device. One point goes to the default usb port tap. The tap has an otg on off switch routed to the outside of the device. one point has my 64gb usb drive on it. the last will probably go to a 3g attennae at some point.
The tap is currently ruined. I've since relaced my 30 dollar radio shack iron with $300 in hakko equipment and am waiting on a new io assembly to arrive to test a more sturdy method.
I have the back of my nexus dremeled to make room for the additional electronics. A clear semi flexable snap on back from china re-encloses the hole with enough extra room to keep the parts while revealing the mod.
Progress pictures in the next few days. Then hopefully completed pictures in the next few weeks if all the parts come in.
The tap is currently ruined. I've since relaced my 30 dollar radio shack iron with $300 in hakko equipment and am waiting on a new io assembly to arrive to test a more sturdy method.
I have the back of my nexus dremeled to make room for the additional electronics. A clear semi flexable snap on back from china re-encloses the hole with enough extra room to keep the parts while revealing the mod.
Progress pictures in the next few days. Then hopefully completed pictures in the next few weeks if all the parts come in.
Just a suggestion...
I'm new to all of this and not sure if this would be any help but do you guys think it be of any use to look at another tablet or phone that has a an internal usb and try to mimic the layout/method?
It looks like alot of work has been put into this and it would suck to see this die. What you all have done has been amazing and I hope this project will get completed!
I'm new to all of this and not sure if this would be any help but do you guys think it be of any use to look at another tablet or phone that has a an internal usb and try to mimic the layout/method?
It looks like alot of work has been put into this and it would suck to see this die. What you all have done has been amazing and I hope this project will get completed!
Here's is a pretty nice hub.
This has a Micro USB connecter, USB port, mini/mirco SD card slot, SD card slot, and micro USB port. I like the options it gives but don't really know how well it would fit inside the already tight area.
whiterabbitexpress .com.... /card-reader/
This has a Micro USB connecter, USB port, mini/mirco SD card slot, SD card slot, and micro USB port. I like the options it gives but don't really know how well it would fit inside the already tight area.
whiterabbitexpress .com.... /card-reader/
Love this hardware mod....
Sorry to dig this thing up from so long ago, but would it be possible to rehost those first images? im attempting to do something similar with mine now that I no longer depend on it for school. Thanks
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8The 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 done4So 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.3I'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.
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