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This article is about converting a tablet keyboard to a USB device. I have a couple of old tablet cases with an integrated keyboard & touchpad for UMAX visionbook 10Wi-S. It was laying around, being useless and collecting dust. And I have decided to convert it to a standard USB keyboard to be used with single board computers (raspberry pi, orange pi, etc), servers, and other devices. 

Umax visionbook 10wi-s

The visionbook uses a 5-pin connector to link with the keyboard. This is almost always a USB connection - I had only the keyboards, no tablet available so I could not check that in the Windows Device Manager (yes, it's a Windows-based device). But the USB was my first choice and just to be sure & also to find out each pin's purpose, I have decided to sacrifice one piece of keyboard and do an autopsy on it. And also because It's fun to open-up things :-D

visonbook keyboard

Here is a quick look at the boards inside: I have disconnected the keyboard ribbon cable to get a better look at it & also removed the sticker from PCB (it's now on the right of the PCB)

Inside the keyboard

And this was quite easy, because the PCB has test points labelled as D+ and D-, so the only pissing pins now are the power pins (+5V and GND). And finding these will not cause a brain injury to anyone. Let's zoom in a bit.

Inside pinout

So the tablet uses 5 pin connector, its connected via ribbon cable to a 6-pin connector, but only 5 lines are used. From top to bottom we can see, that the first pin is not used, second and third are connected to the ground (GND).

The fourth and fifth pins are clearly identified by test point labels as D+ and D- and the sixth pin must be the power. Why? Because it has to be powered somehow and there is no other pin :) Yes, I could try to read the chip type, look for a datasheet, check pins & voltage, and so on. But why bother with that - it's standard USB in most cases and there is no reason this should be different. You could say, I took the leap of faith, I say I was sure about that :-)

The only thing that needed to be done was to take a multimeter, check which pin of the ribbon cable is connected to which pin of the tablet connector, and the result is not very surprising:

Connector pinout

For the test run I have soldered an old USB cable according this pinout and connected it to my computer. The result in linux is this:

~$ dmesg -T | tail 
[St mar  2 10:49:27 2022] usb 3-3.3: new low-speed USB device number 26 using xhci_hcd
[St mar  2 10:49:27 2022] usb 3-3.3: New USB device found, idVendor=1018, idProduct=1006, bcdDevice= 1.00
[St mar  2 10:49:27 2022] usb 3-3.3: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[St mar  2 10:49:27 2022] input: HID 1018:1006 as /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.3/3-3.3:1.0/0003:1018:1006.0012/input/input51
[St mar  2 10:49:27 2022] hid-generic 0003:1018:1006.0012: input,hidraw7: USB HID v1.10 Keyboard [HID 1018:1006] on usb-0000:00:14.0-3.3/input0
[St mar  2 10:49:27 2022] input: HID 1018:1006 Mouse as /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.3/3-3.3:1.1/0003:1018:1006.0013/input/input52
[St mar  2 10:49:27 2022] input: HID 1018:1006 Consumer Control as /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.3/3-3.3:1.1/0003:1018:1006.0013/input/input53
[St mar  2 10:49:27 2022] input: HID 1018:1006 System Control as /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.3/3-3.3:1.1/0003:1018:1006.0013/input/input54
[St mar  2 10:49:27 2022] input: HID 1018:1006 Wireless Radio Control as /devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.3/3-3.3:1.1/0003:1018:1006.0013/input/input55
[St mar  2 10:49:27 2022] hid-generic 0003:1018:1006.0013: input,hiddev2,hidraw8: USB HID v1.10 Mouse [HID 1018:1006] on usb-0000:00:14.0-3.3/input1

The keyboard & touchpad are working just fine.

So that's it for now, I will replace the original connector with a micro USB and/or USB-C connector and this will be a fine keyboard for emergency situations.