White PDN Serial Interface
RobBrownNZ's Original Instructions and images at Cobbleware.com
Reposted here with permission. THANKS, Rob!
NOTE: I'm offering this guide in the hope that it will be useful. While you are welcome to use this description as a guide to connecting a serial interface to your PDN, I will not accept any responsibility for the consequences. It's all at your own risk.
With that out of the way, this page is about connecting a serial interface to the CON4 connector inside a White Pandigital Novel. This has been discussed on SlateDroid, head over there to see the details. In particular, I won't explain how to disassemble your PDN as there are guides on SlateDroid. I'll just give the standard warning: there are lots of parts that are held together with double-sided tape, don't bend the plastic too hard or you'll break it!
The schematic for the adapter is shown below. R1 needs to be there, its value should be around 3k - 5k. I used 4k7. R2 is optional, if you don't put it in then you may find that the PDN powers up when you connect USB to the adapter. That's not a great thing so I'd generally recommend that you put R2 in. Value should be 1k - 5k, I used 1k5.
You'll notice that pins 1, 2, and 4 on the PDN are all "+3V3". They're connected together in the PDN, and so you can connect to whichever of them is convenient for you- there's no difference at all. The same goes for "GND" on pins 3, 8, 14, and 18.
First, you need to gather the parts:
- Flat flex adapter board - Digikey
- 20-way flat flex (I used the 3" one) - Digikey
- USB-to-Serial adapter I like this one from - SparkFun
- Resistors - I used a 4k7 (R1) and a 1k5 (R2), but as I said, it's not critical. A couple of 3k3s would be fine. Any half-decent electronics store should have them: Radio Shack (USA), Dick Smith (Australia/NZ) etc.
- Hookup wire, soldering iron and solder, etc.
Now prepare the resistors by bending one lead over 180 degrees so that the two leads are parallel, and then bend both leads 90 degrees a couple of millimetres below the body of the resistor. If you have needle-nosed pliers, clamp the leads between the body of the resistor and the bend, as this will prevent the resistor from being stressed while you bend the leads.
Next, trim the resistor legs so that they have just a short protrusion after the 90 degree bend - a couple of millimetres or so.
Solder the resistors to the PCB. When looking at the board as shown in the picture below, R1 is on the left.
I've indicated the pin numbering on the adapter board, in red.
Add 3 short wires:
- From pin 4 to the end of R1 that's further from the centre of the PCB. Remember you could use pin 1 or 2 instead of 4.
- From pin 10 to the end of R2 that's closer to the centre of the PCB.
- From pin 9 - it will go to the end of R1 that's closer to the centre of the PCB, but don't attach the other end yet.
Add the wires that will connect to the USB-Serial adapter. The PDN's Tx wire (yellow in the picture below) has to go through the same hole as the wire from pin 9 that you didn't connect before. You might find it easier to twist the ends of the two wires together before putting them through the hole in the PCB. They connect to the end of R1 that's closer to the centre of the PCB.
The PDN's Rx wire (brown in the picture) connects to the end of R2 that's further from the centre of the PCB. The GND wire (black in the picture) goes to pin 3, 8, 14, or 18 - in the picture I've connected it to pin 8.
Now connect the wires to the USB-serial adapter. Tx and Rx are swapped, so the yellow wire (PDN Tx) goes to the USB-serial adapter's Rx input. The brown wire (PDN Rx) goes to the USB-serial adapter's Tx output.
Finally, connect it all together. The flat flex needs to have its contacts down when viewed from the angle in the picture below.
Connect the USB-serial adapter to your PC and configure a serial terminal program for 115200 bits per second, no parity, 8 data bits, 1 stop bit, and no flow control. For a terminal program, I prefer TeraTerm.
When you power up the PDN, you'll see messages from U-Boot, the Linux boot process, and Android starting up. If you bang on your keyboard immediately after powering up (or resetting) the PDN, you can interrupt U-Boot and type commands to it (start with "help").
I'd be interested in any feedback anyone may have on these instructions. Hop on over to the SlateDroid forum and join the discussion!
Edited by mrsburnout, 01 August 2012 - 09:39 AM.