Add a Serial port to the ARM9 Linkstation

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Contents

Introduction

Note
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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

LS Pro Mainboard Backside serial.JPG
Pinout - Ground is on the Right side

Pin  Signal
1 Transmit (TX)
2 Receive (RX)
3 Power (3.3V)*
4 Ground (GND)

Serial LS Pro prepared box for serial.JPG

Project of creating ready2use serial cables

Anyone who wants a cable please add his name to the lists below.

List of developers who want a prebuilt serial cable:

  • georg
  • jonli447
  • mindbender
  •  ?


List of kurobox.com-contest winners that will get a prebuilt serial cable:

  • russk
  • tampakuro/kuroguy
  • lyakh

Revogear does not respond to any mails anymore, so waite decided to use the donations to buy LS Pros for these guys instead.


List of user who want a prebuilt serial cable:

  • khisanth
  • cakalapati
  • MichaelWeiser
  • mesterS
  •  ?



Here some pictures from the build-process (mindbender had fun with it)
Serial cables LS Pro some cables.JPG
I opened all FutureDial Cables to check if all cables used the same color-coding + Profilic-Chip:
Profilic chip check1.JPG
Profilic chip check2.JPG
Prebuilt cables will use a heat-shrink-tube to make the cables more stable. Four finished cables.JPG


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

Models other than KuroPro
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If you are attaching a serial header pin onto the main board, you may want to consider:

  • Using the header pin unit with a 90 degree bend, or you might not be able to close the case
  • Soldering it with the pins toward the interior, rather than toward the case. This allows easier access, since if the pins face the case side they would be very close to the metal side. This would make access is so tight that one might end up taking the board out to get plug fitted on the pins.


Build your own LVTTL/RS232 or LVTTL/USB interface

Buy your own TTL Level Shifter

Usage considerations for the TTL-232R-3V3

TTL-232R-3V3 USB to TTL Serial Converter Cable
A very similar TTL/USB converter cable that uses a chip by FTDI (the same chip is used in the SCON-KIT ) can be obtained, but the pinout at the connector end would need to be reassigned: Spec Sheet w/ pinout, wire colors & other info
MM232R.jpg Mouser Part # 895-TTL-232R-3V3 $20.00
4pinheader.gif Mouser Part # 517-929400-01-04 $0.32

A working/tested pinout/wire-color scheme is:

Color Pin Number Signal
yellow 1 TXD
orange 2 RXD
unused 3 VCC
black 4 GND
  • 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.