Digital Media Player Asus Oplay serial TTL USB Console Firmware Porting

This tutorial describes how to plug the serial ttl usb port in you Asus O'Play to your PC and access oplay through the serial console.

This might come in handy if you "brick" your oplay or otherwise need console access like when you replace Busybox with a new version that has a different telnet daemon...

YOU MIGHT BREAK YOUR OPLAY IF YOU CONNECT THINGS WRONG. PROCEED AT YOUR OWN RISK!!!

You can't just connect the 4 pins in your oplay motherboard to a PC USB port. You need a Serial TTL USB kit or some USB data cable that already has a transceiver. You can use Nokia CA-42 or DKU-5 data cable.


Other than that you only need a way to connect those 4 pins on the motherboard to the CA-43 cable. I will place a USB port to the back of my oplay since I don't want a cable sticking out of the oplay all the time.

Let's get going!

remove the small pads in the four corners of the bottom of the oplay unit.

remove the top of the cover.

Be careful with the aluminum shield, since it has a fragile connector to the wifi antenna. I almost broke the connector because I had to reopen the case for 5 times to get this working. I connected wires wrong or some other crap happened.

You can disconnect the wifi antenna so you won't break it.








What you need cable wise is a 4pin connector that fits the motherboard serial connector (or just solder the CA-42 wires to the motherboard)



I was going to use an audio cable that connects cd-rom's audio drives to motherboards, but they only got 3 pins connected.

Next one was an Intel processor cooler with a right type on connector, but I wouldn't want to make a working cooler useless.



So I rummaged through my extensive cable closet and there it was!




A set of extra USB-ports that come with a motherboard when you buy it. It has the right connector for the motherboard AND a female USB connector on the other end. That means I could attach the female end to the case and use a separate cable to use my serial TTL USB port when ever I need to.

Pin order is not the same than on a USB. That means I would have to use a custom USB cable when I connect to oplay.

If I stick a regular USB cable (or some1 does) I will get 5V straight to ground and something will melt.

I will break up the header so it will have the same pin order as a regular USB (Vcc, Rx, Tx, GND).

I reconnected the small cables so that they will match a USB pin layout. That way I don't have to use a custom cable to my new USB port.

No extra cables coming out of my oplay if I'm not using the recovery serial cable.

Oplay casing has a matching spot right on top of the digital audio and HDMI connectors. I can screw my female connector there and don't have to break the case entirely. This is going great!



Now I only need something to cut metal with. Since I don't have even pliers I will use a dremel... Don't do this at home plz. Notice that I'm also using protective gear...





So I was able to cut (melt...) the shielding and get the hole ready for my female USB.




So the last guy that took my drill heads didn't bring them back. No worries. I will just superglue this piece of **** together and hope it is going to work. I mean it will never come off if I fuck it up.

At this point it is good to check which pin is which pin on the female USB connector. This makes it a lot easier to connect them to the right pins on the PC. I used a digital multimeter with a contact BEEP to identify the pins.

Yes I didn't think of this and I was forced to disassemble the box again...




When the cables are nicely tucked inside and the glue is dry assemble the shielding case first. Be careful when you connect the wifi antenna back so that the connector won't break.



I used a wood drill to make a small hole in the oplay plastic cover so that my new USB port is visible.

So now I notice the bracket in the back is blocking our new TTL Serial port. Gotta cut that out.



Here is the finished product




Now it's just screws back in and I hope the rubber pads still stick.

I was just going to stick this "bomb" to my PC, but just to be safe I read some web pages about this.

http://buffalo.nas-central.org/index.php/Use_a_Nokia_Serial_Cable_on_an_ARM9_Linkstation
http://www.nslu2-linux.org/wiki/HowTo/AddASerialPort

It happens I have a Nokia CA-42 cable and I'll chop that up for my project.



You can't just snap 2 USB cables apart or use a straight cable. You need to have a transceiver in between. Nokia CA-42 has one in the USB connector so that is why I'm using it.

You can also order USB TTL cable straight from ebay with the pins already attached.

EBay

Then make a cable that connects the right Asus pins to correct USB pins. Here is a pin layout

Pinouts.ws

So don't just connect same colors together. Verify that the oplay data+ goes to USB Data+ and oplay GND goes to USB GND.

You need to connect also the Vcc 3.3V pin or the Nokia CA-42 transceiver wont power up.

!!!Remember that 3.3V goes into USB red cable and ground (GND) from oplay goes into USB black cable. If you short the 3.3V into the ground you will get some smoke and something will turn into a light bulp or get destroyed.!!!

If you connect the Rx and Tx (Receive and Transmit) the wrong way around you won't just get any data going through.



Get a Virtual COM port driver from ftdichip and install it.

http://www.ftdichip.com/Drivers/CDM/CDM20802_Setup.exe

I stuck the cable into my PC and powered up Oplay.



Windows XP tells me that it has found new hardware (USB device) and wants to install new software.

It seems I have previously installed Nokia PC Suite since it wants to install Nokia Drivers. If you don't get this automatically just install Nokia PC suite first.

Nokia Suite

It will install Nokia CA-42 phone parent and a modem. Both installations must succeed.

After installation reconnect the Nokia CA-42.

Start Hyperterminal (or any other terminal software like Putty). Next steps are from Hyperterminal.

Start Hyperterminal from Start/Programs/accessories/Communications

It asks for a name to this new connection. Give it a name like oplay.



Next choose COM3 (or what ever number it has installed your setup)



Select following Port Settings.

Bits per second: 115200

Databits: 8

Parity: None

Stop bits: 1

Flow control: None



If you did everything right you should be getting shit loads of debugging messages from oplay!

We are connected!!!!!



Next what you need is a server that can serve a working install.img to the oplay.

I have an FTP server running and I put a new install.img to it. I downloaded the image with a browser just to make sure that an anonymous download works for the image.



Next I will go back to my Hyperterminal and type

stopall and hit the enter key

Debugging should stop since it stops the RootApp and DvdPlayer. You are now in a root console to the oplay.



Make sure you can connect to your ftp server. Hook up oplay with an Ethernet cable to the same network where the FTP server is.

Oplay has the address 192.168.0.9 when it boots up. If this does not fit your network you can use the

ifconfig eth0 192.168.0.9

command from Hyperterminal root console to change any address you like.

Check with ping that you can connect to your ftp

ping 192.168.0.15



Tell the oplay where the new image is AND REMEMBER TO USE YOUR OWN ADDRESS!!!

echo "ftp://192.168.0.15/sda1/install.img" > /tmp/installing_source

Start the recovery.

kill -6 1



You start getting a lot of text from the console and the install will take few minutes.



Then it finally reboots and you start getting the debug messages again in the console.

You just unbricked your oplay! Congratz!!

Serial console is also very nice if you have locked yourself out of your oplay. I have done this few times with replacing Busybox and the new version has different Telnet daemon that will not work with default inetd.conf setup.