Modding the Uselss Dock into the Ultimate Media Dock!

Bxsteez · Sep 27, 2011

I'm thinking i might have some Serial data issues but I'll have to hook up a scope to my first build and see. If i do I will just have a some line drivers in there and that should clear up most of those issues. I think the on the other side of the connector on the GTAB there are some line drivers/buffers so I might be OK. I will try and build a board tonight and get a bill of materials written up and try this thing out.

---------- Post added at 01:35 PM ---------- Previous post was at 12:45 PM ----------

I did not expect to run into the situation of not being able to find the female gtab connector. I might either change the design to two USB ports, one male and one female or I might just buy a desktop dock and create a board of the same size and install it in there.....

jonnyg1097 · Sep 27, 2011

I love that there is discussion about this. If you guys end up being successful with this I would definitely pay to get one.

Id love to see a (micro) sd slot as well as the other slots previously mentioned but maybe I am getting a bit greedy.

Bxsteez · Sep 27, 2011

jonnyg1097 said:
I love that there is discussion about this. If you guys end up being successful with this I would definitely pay to get one.

Id love to see a (micro) sd slot as well as the other slots previously mentioned but maybe I am getting a bit greedy.

That might be possible... I dunno about that one. I think after I get the non powered USB hard drive as well as the Host + Charging working i'm going to try and get HDMI to work as well. Then i'm going to have to buy a Gtab 7inch dock... UGH..

used2hvatreo · Sep 28, 2011

Bxsteez said:
That might be possible... I dunno about that one. I think after I get the non powered USB hard drive as well as the Host + Charging working i'm going to try and get HDMI to work as well. Then i'm going to have to buy a Gtab 7inch dock... UGH..

mine gets delivered tomorrow, i will try and find the link but I got it for like $18 + free shipping. Getting HDMI working is going to be next to impossible though. The tab outputs in MDL or MHL or something like that, and you need a decoder chip that will make that into regular HDMI, hence their stupid accessory. IF someone wanted to bust open that little guy, we could try and locate the chip they use. Its the same thing they use for a lot of their devices.

Bxsteez · Sep 28, 2011

used2hvatreo said:
mine gets delivered tomorrow, i will try and find the link but I got it for like $18 + free shipping. Getting HDMI working is going to be next to impossible though. The tab outputs in MDL or MHL or something like that, and you need a decoder chip that will make that into regular HDMI, hence their stupid accessory. IF someone wanted to bust open that little guy, we could try and locate the chip they use. Its the same thing they use for a lot of their devices.

That shouldn't be a big deal assuming the chip isn't super expensive. I would think I could bust open the 7inch dock and see what part they use or use a different device. I'm sure the one they use isn't the only game in town..

This is the circuit I have for the switching of the 5V in and out. Don't pay too much attention to the resistor values since they haven't been fine tuned yet. Tell me what you guys think..

used2hvatreo · Sep 29, 2011

Bxsteez said:
That shouldn't be a big deal assuming the chip isn't super expensive. I would think I could bust open the 7inch dock and see what part they use or use a different device. I'm sure the one they use isn't the only game in town..

This is the circuit I have for the switching of the 5V in and out. Don't pay too much attention to the resistor values since they haven't been fine tuned yet. Tell me what you guys think..

Looks great, post your your board layout when you are done and I will take a look at that as well, but I think it should work. As far as the decode chip, I will look around for that

Bxsteez · Sep 29, 2011

I think i've decided that instead of modifying the actual desktop dock i'm going to make an adapter that can either plug into the tab by itself or to the other docks. It will also give me the ability to remove the female 30pin connector which no one sells.

What do you guys think?

used2hvatreo · Sep 29, 2011

Bxsteez said:
I think i've decided that instead of modifying the actual desktop dock i'm going to make an adapter that can either plug into the tab by itself or to the other docks. It will also give me the ability to remove the female 30pin connector which no one sells.

What do you guys think?

That was what I was thinking about doing originally. You can do the pass thru for power and just use a USB micro female instead. The only thing you might want to incorporate is the data lines so that people can plug straight into this adapter from their pc so that they can do transfers and whatnot without removing the adapter and plugging the 30-pin back in

As far as MHL is concerned, the chip we want is a MHL bridge. I don't know if anyone else makes them, but here is one:

MHL Bridge

Bxsteez · Sep 29, 2011

Well that might be a bit more complicated but not impossible. That would mean I couldn't strap the ID to USB host. It would have to change depending upon what device is plugged in. Not impossible... Maybe i can use some sort of a varistor setup. Let me think about that idea and see if I can come up with a way to adapt that resistance.

used2hvatreo · Sep 29, 2011

Bxsteez said:
Well that might be a bit more complicated but not impossible. That would mean I couldn't strap the ID to USB host. It would have to change depending upon what device is plugged in. Not impossible... Maybe i can use some sort of a varistor setup. Let me think about that idea and see if I can come up with a way to adapt that resistance.

Are you thinking about it adapting automatically, or would a switch be the easier way to go?

Bxsteez · Sep 29, 2011

A switch would be easier to design but more cumbersome for the user. I'm thinking of it doing it automatically.... assuming i can figure out a way.

used2hvatreo · Sep 29, 2011

Bxsteez said:
A switch would be easier to design but more cumbersome for the user. I'm thinking of it doing it automatically.... assuming i can figure out a way.

Why not just another port? You can put a charging port, usb host port and usb data port.

Bxsteez · Sep 29, 2011

used2hvatreo said:
Why not just another port? You can put a charging port, usb host port and usb data port.

That is a good idea but i believe there are is only one serial pair for the Tab. Then you would only be able to use one at a time but I might make two ports that are different. That would help with the confusion. Maybe a USB B for syncing and USB A for USB Host. Hmmmmmm... I have to think about it a bit. I have to make this adapter as cheap as possible too so i have to be a little relaxed on the circuit components.

It sucks not being large enough to buy 10000 FETS or resistors. They are expensive when you only buy like 10 or 100. So far the parts are only 2 or 3 bucks, of course that is excluding the PWB and whatever housing i use to package this thing.

Bxsteez · Sep 30, 2011

I was looking over my schematic this afternoon with a coworker and it looks like i have my PMOSes oriented incorrectly and on top of that the ground from the wall is likely to be floating so the circuit won't work as it is now. I have to go back to the drawing board and correct it. I will update......

Still trying to figure out why my simulations worked.

used2hvatreo · Sep 30, 2011

Bxsteez said:
I was looking over my schematic this afternoon with a coworker and it looks like i have my PMOSes oriented incorrectly and on top of that the ground from the wall is likely to be floating so the circuit won't work as it is now. I have to go back to the drawing board and correct it. I will update......

Still trying to figure out why my simulations worked.

Your simulations worked because you have used the same ground everywhere. If you are using the NI Circuit Designer then you definitely have the same ground. When you switch over to design your board, you will have to run a trace for the ground as well, but in the circuit design phase it lets you simulate by just putting the ground symbol there.

As far as the ports go, I was thinking the same thing. mini-USB for charging, micro-USB for data. As far as host, I'm not sure what can and can't be done at the same time.

Also, I was just looking around, and maybe the version 1 answer for HDMI is to simply map the MHL lines to another micro-USB port, and then allow the use of other cheaper usb to hdmi adapters, like the one I found for 11.99 on amazon

Bxsteez · Sep 30, 2011

used2hvatreo said:
Your simulations worked because you have used the same ground everywhere. If you are using the NI Circuit Designer then you definitely have the same ground. When you switch over to design your board, you will have to run a trace for the ground as well, but in the circuit design phase it lets you simulate by just putting the ground symbol there.

As far as the ports go, I was thinking the same thing. mini-USB for charging, micro-USB for data. As far as host, I'm not sure what can and can't be done at the same time.

Also, I was just looking around, and maybe the version 1 answer for HDMI is to simply map the MHL lines to another micro-USB port, and then allow the use of other cheaper usb to hdmi adapters, like the one I found for 11.99 on amazon

Oh i know why the grounding the p-channel gate worked and why it won't work in real life but it was the fact that the P-channel is backwards and the output still worked.

I think i figured it out. I think current is flowing because the voltage is biasing the body diode and the current flows enough to raise the source voltage (load voltage) enough to breach the threshold point and turn on the FET. Its all kinds of wrong with the right answer lol. It was a silly error on my part. I have another idea but its going to force me to add a third FET which I was trying to avoid.

On the connectors. I don't think the ternminals for Micro USB can carry enough current to support chargin the tab at 2A. I could be wrong. I think cellphone charges use 1A. I have to check on the specs.

used2hvatreo · Sep 30, 2011

Bxsteez said:
Oh i know why the grounding the p-channel gate worked and why it won't work in real life but it was the fact that the P-channel is backwards and the output still worked.

I think i figured it out. I think current is flowing because the voltage is biasing the body diode and the current flows enough to raise the source voltage (load voltage) enough to breach the threshold point and turn on the FET. Its all kinds of wrong with the right answer lol. It was a silly error on my part. I have another idea but its going to force me to add a third FET which I was trying to avoid.

On the connectors. I don't think the ternminals for Micro USB can carry enough current to support chargin the tab at 2A. I could be wrong. I think cellphone charges use 1A. I have to check on the specs.

I was definitely going more for the idea of multiple diff ports so it would be straight forward as to which port did what, but yeah, def check it out, would hate to be responisble for burning up something because it couldn't handle the amps

jonnyg1097 · Oct 15, 2011

Are there any updates on this? I would hope this is still getting done-

Bxsteez · Oct 16, 2011

No updates yet. I've been kinda swamped with work so I haven't had a chance to update the schematic or start on the layout. Its coming though

mailings · Feb 29, 2012

used2hvatreo said:
Also, I was just looking around, and maybe the version 1 answer for HDMI is to simply map the MHL lines to another micro-USB port, and then allow the use of other cheaper usb to hdmi adapters, like the one I found for 11.99 on amazon

Did you made this? I'm really interested in building this as an adapter. I have a Galaxy Nexus and a TAB. With shomething like this I could use the same MHL to HDMI adapter with both devices.

Modding the Uselss Dock into the Ultimate Media Dock!

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