Author Topic: Schematic for m7206 dongle  (Read 2877 times)

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Offline coreire

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Schematic for m7206 dongle
« on: January 22, 2012, 11:25:07 PM »
This is a long shot, but does anyone know if a schematic is available for the dongle that comes with the m7206/m799ca?
The dongle I have is the m7206b-ZJ-V1.2, but any schematic of even a similar dongle would be a help.
I want to fit the usb ports inside the tablet and I have been mapping out the connections. The problem is that there is a component in the circuit on the dongle's PCB that I am unsure of. It's labelled U4 and it's in series with the +5V output of the usb port.

Offline robotop

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Re: Schematic for m7206 dongle
« Reply #1 on: January 23, 2012, 01:43:35 AM »
hello, can you post here a macro picture of the circuit ? I haven't seen (for now) such dongles; may be the IC is simply a low-drop regulator from 5V to 3.3V for supplying some other part of the circuit, but a good picture can help to be right. Please, what's the typical connection of the dongle ? What sort of "mapping" have you done with the contacts ? Some additional infos can help me to understand. I don't know if I would be able to help you, but we are here for experimenting... :)
Almost any problem can be solved by a quiet sleeping night...

Offline Neko Ed

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Re: Schematic for m7206 dongle
« Reply #2 on: January 24, 2012, 08:27:10 PM »
I don't remember any components inside the dongle to mine, but it was a while ago that I looked. Mine has two USB ports and an ethernet port, and if I remember correctly they're just straight connections off of the connector on the tablet.

Take a picture, and I'll dig mine out and compare. It's entirely possible there's a bunch of different dongles out there.

Offline ramones

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Re: Schematic for m7206 dongle
« Reply #3 on: January 25, 2012, 12:51:29 AM »
I opened mine up for a look. Here's a pic:
http://omg.wthax.org/100_0838.jpg

Offline robotop

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Re: Schematic for m7206 dongle
« Reply #4 on: January 25, 2012, 02:01:34 AM »
I think Coreire talks about a different dongle. If there is an IC with label U4, may be there are U3, U2 and U1 somewhere...
The dongle you shown hasn't any IC onboard and is (exactly as Neko Ed said) just wiring connection from the 24 pin socket to USB #1, #2 and LAN (and TTL serial, obviously), with additional capacitors needed to absorb power glitches.

P.S. btw, nice photo, good macro. If you want, take a look at other dongles I have opened and modded here:
http://ficara.altervista.org/pages/tablet-env/ficara_tablet-env.htm

EDITED: Oops, Coreire talked about a "component", not "IC"... may be I'm wrong ? Please, Coreire, add some info, thank you.
RE-EDITED: yes, I'm wrong. The circuit label supplied by Coreire is exactly the same in the picture of Ramones (btw, U4 is a decoupling capacitor). Now, I don't understand why you need for a schematic of such simple circuit, just wires... but, look in the forum for this file: cmx_wms8650.7z ; it's the schematic of a tablet and has the pinout of 24 and 30 pins connectors.
Re-Re-Edited: it seems that the original file isn't reacheable, so I will attach just the part that you will need here...
« Last Edit: January 25, 2012, 02:43:36 AM by robotop »
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Offline jenom

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Re: Schematic for m7206 dongle
« Reply #5 on: January 25, 2012, 07:03:22 AM »
I have the M7206B-ZJ-V1.2 in my hand
The letter "U" refers to the connectors on the board: U3 is the LAN, U1 and U 11 are the USB connectors.
Strangely, there is also U4 and U5 , and they are not connectors for sure !
Used a digital multimeter to measure them, they do not have any resistance, so in my opinion they are CAPACITORS !
There are 4 holes there for serial connection at the bottom-left corner:
From left to right (same position as the picture):
GND---TXD--RXD--+3.3 VDC

Offline robotop

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Re: Schematic for m7206 dongle
« Reply #6 on: January 25, 2012, 09:57:34 AM »
Hello Jenom. Do you read all the posts in the thread ? If you don't, please do. The picture sent by Ramones is very neat and clear ; also I said the U4 (in that picture) is a decoupling capacitor. Ok, bye.
Almost any problem can be solved by a quiet sleeping night...

Offline jenom

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Re: Schematic for m7206 dongle
« Reply #7 on: January 25, 2012, 04:51:30 PM »
@robotop
good to hear that we both agree on the "capacitor"
it never harms anything if others verify what one says, isn't it ?

Offline Neko Ed

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Re: Schematic for m7206 dongle
« Reply #8 on: January 25, 2012, 04:54:09 PM »
Okay, I didn't realize that was a serial port, this is good, it could be a way into the inner workings of the device!

It looks like 3.3V LVTTL serial, which will require a 3.3V TTL-to-RS232C level shifter. Once you have that though, we may have the master key to doing all sorts of things to this device.  8-)

Offline jenom

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Re: Schematic for m7206 dongle
« Reply #9 on: January 25, 2012, 05:26:20 PM »
@neko ed
I have a working Rs232-serial converter, used it with a few WM8650 tablets to connect dongle to PC and I was able to get some useful info from u_boot using windoz HyperTerminal (115200, 8,N,No Flow)
the bad new is , connected the same circuit to the M7206 dongle 4 pin serial and did got anything out of it   :android-sad:
tried to reverse the TXD, RXD lines...no change    :android-shocked:

Offline Neko Ed

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Re: Schematic for m7206 dongle
« Reply #10 on: January 25, 2012, 06:51:07 PM »
@neko ed
I have a working Rs232-serial converter, used it with a few WM8650 tablets to connect dongle to PC and I was able to get some useful info from u_boot using windoz HyperTerminal (115200, 8,N,No Flow)
the bad new is , connected the same circuit to the M7206 dongle 4 pin serial and did got anything out of it   :android-sad:
tried to reverse the TXD, RXD lines...no change    :android-shocked:

Try fooling around with the baud rate settings, it might be that it uses a slower speed. If that fails we may be out of with the dongle, but there MAY still be a serial port somewhere on there. Perhaps the missing cap may be affecting transmission? Could be anything, gotta try a number of things before calling it failed.

Offline jenom

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Re: Schematic for m7206 dongle
« Reply #11 on: January 25, 2012, 07:35:10 PM »
tried the M7206 dongle with a Wm8650 tablet....it worked....so missing components makes no difference
at the beginning, when i started with Wm8650 my settings in Hyperterm were  wrong (baud rate/flow control) but I still get a "garbled" reply on the screen......from the M7206......not a peep !   :android-sad:

Offline coreire

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Re: Schematic for m7206 dongle
« Reply #12 on: January 27, 2012, 04:24:02 AM »
I think Coreire talks about a different dongle. If there is an IC with label U4, may be there are U3, U2 and U1 somewhere...
The dongle you shown hasn't any IC onboard and is (exactly as Neko Ed said) just wiring connection from the 24 pin socket to USB #1, #2 and LAN (and TTL serial, obviously), with additional capacitors needed to absorb power glitches.

P.S. btw, nice photo, good macro. If you want, take a look at other dongles I have opened and modded here:
http://ficara.altervista.org/pages/tablet-env/ficara_tablet-env.htm

EDITED: Oops, Coreire talked about a "component", not "IC"... may be I'm wrong ? Please, Coreire, add some info, thank you.
RE-EDITED: yes, I'm wrong. The circuit label supplied by Coreire is exactly the same in the picture of Ramones (btw, U4 is a decoupling capacitor). Now, I don't understand why you need for a schematic of such simple circuit, just wires... but, look in the forum for this file: cmx_wms8650.7z ; it's the schematic of a tablet and has the pinout of 24 and 30 pins connectors.
Re-Re-Edited: it seems that the original file isn't reacheable, so I will attach just the part that you will need here...


Sorry for the late reply, I didn't get a chance to get online much the last few days.
Thanks for the info. I didn't need the schematic to work out the circuit, I just follow the tracks for the corresponding pins for that. I only wanted the schematic in the hope that the symbol for component U4 would be on there.
The dongle that I have is identical to the one in ramones picture, so I guess it is just a decoupling capacitor as you said. The "U" label just threw me off, I would have expected "C" as the spaces for other capacitors are marked on the board.
Thanks.

 

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