Add a Serial port to the ARM9 Linkstation
- 1 Introduction
- 2 The Serial Converter
- 3 Using a USB Plug to form a friction-fit connector
- 4 Have fun!
|The same instructions will work for a KuroBoxPro|
What you can do with serial access on a LS Pro
At first: check serial access
In fact you can control the UBoot Bootloader.
- You can change to EM Mode at will without any dirty tricks.
- You can look at the linux system of your LS pro without having to flash any custom firmware
- You can load a kernel + ramdisk via tftp
- Hey! We connect it because we can!
Serial access isn`t that important for users, but it is very important for developers because they
exactly see what is happening while the LS Pro boots.
The kernel log tells us a little more about the hardware and it allows us to debug a newer kernel.
Without serial that is not possible.
Why it is easy to gain serial access on the LS Pro
The Serial Converter
The serial port signals from the processor are only 3.3V. For proper RS-232 12V signaling, an RS-232 level shifter needs to be added. These are very common in PDA serial cables also, but can be purchased
Build your own LVTTL/RS232 or LVTTL/USB interface
- LVTTL/RS232 - Building a Custom Serial Interface
- LVTTL/USB - Use a Nokia Serial Cable on an ARM9 Linkstation
- LVTTL/USB - Use a cheap phone sync cable with the serial port
Buy your own TTL Level Shifter
- LVTTL/RS232 - MAX232 based from Futurelec - MINIRS2323V
- LVTTL/USB - FTDI chip based cable - TTL-232R-3V3
Usage considerations for the TTL-232R-3V3
A working/tested pinout/wire-color scheme is:
- Solder the 4-pin header to the board. Make sure you don't have shorts.
- You will need to switch wires on the TTL-232R-3V3 cable. Use a sharp object to lift the plastic tabs and carefully pull the wires out. Rearrange them according to the table above (black, empty, orange, yellow, empty, empty) and slide those wires back in. Tape the other wires to make sure they don't short anything.
- When plugging in the cable, make sure black aligns with GND, yellow with TXD, and orange with RXD.
- Connect the USB cable to your computer, start a terminal program with the right settings.
- Turn on the device, you should see output from the bootloader in couple seconds.
Using a USB Plug to form a friction-fit connector
1) You will also need an old USB-plug (Female, Type A). I used two from USB-extender-cables and the rest from female-USB-connectors that i directly ordered in a shop.
2) you will also need something as thick as 1 mm. This can be wood, plastic or the latest flyers you collected by going out at the weekend. We used a Eurocard which we broke in Pieces (4 rows * 9 holes)
Prepare the USB-Plug
If you are using one from an extender cable
Best would be to use a grinder. Do not hesitate to destroy the cables. It is recommended to remove everything so that you can solder the cables from the phonesync-cable directly to the pins.
If you have bought the part directly
Just open the metal-case and use a grinder to make it look like the picture above. You won`t have to remove any glue or cables.
Checking the cable/plug
Best with a Voltmeter. To go completely safe test from the pins for the yellow + orange wires. The green one + shield can be tested from the pin on the other side.
Solder the phone sync cable to the USB-plug
You will have both read and write access if you solder it that way.
In this picture: Green is GND, Yellow is RX (as in "data entering the LSPro") and Orange is TX (as in "data coming from the LSPro"). The not connected terminal is VCC.
(in this case from on top of the profilic chip from this article: Use a cheap phone sync cable with the serial port).
Cable is confirmed to work...here, hyperterminal is used in WinXp