Add a Serial port to the PowerPC Linkstation

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The console is the text output device for system administration messages. These messages come from the kernel, from the init system and from the system logger. On modern small computers the console is usually the computer's attached monitor and keyboard. The LinkStation, however, doesn't have monitor output; instead, it uses a serial connection for console output. Not only does the serial console provide valuable debugging output, it also allows root access!

Most of this information courtesy of http://www.type-g.com, http://www.kurobox.com, http://www.tldp.org, and John Taylor.

Also look at: How to attach a serial port to the Kurbox/KuroboxHG


Contents

Prerequisites

  • (1)Electronic-grade soldering iron
  • (1) 0.015", 1 oz silver-bearing solder
  • (1) Desolder braid, solder sucker, or Servisol Soldamop
  • (1) 0.1” series PCB header plug, 4-way
  • (1) Serial converter (or build your own - see Stage 4)
  • (1) Tweezers
  • (1) Anti-static wrist strap%%

Stage 1 - Access the Board

  • Disassemble the LinkStation.
  • Remove the main circuit board by removing the 4 mounting screws:
  • Place the circuit board on a static-free work area:

Pcb.jpg

Stage 2 - Attach Header to the Board

  • The console header needs to be attached to the J1 pad:
  • Remove the preexisting solder from J1:

Consoleheader.jpg

  • Solder the PCB header to J1 so that the pinouts face towards the IDE header:
J1 Pinout
Pin  Signal
1 Transmit (TX)
2 Receive (RX)
3 Power (3.3V)*
4 Ground (GND)

Stage 3 - Enable Full Serial Tx/Rx

To enable write support across the serial port, remove the 10K ohm pullup resistor from R75 and install it , or another 10K ohm pullup resistor, to R76.

Desoldering Tip

To desolder an SMD resistor you can apply the following trick:

  • Take a short piece of blank wire and bend one end into a small U-shape using some small pliers. The U-shape should be as such that you can touch the sides of both ends of the resistor at the same time. The width of the U should basically be the length of the resistor.
  • Wrap the other end of the wire around the tip of your soldering iron - while it is still cold. You now have a small U-shaped tool to remove the resistor.
  • Heat up the iron. When the wire is hot enough, heat up the solder at both ends of the resistor and gently pull the resistor away from the pads with the U-shaped tip. Be careful, the resistor likes to end up on the floor.

Stage 4 - The Serial Converter

The serial port signals from the processor are only 3.3V. For proper RS-232 5V signaling, an RS-232 level shifter needs to be added. These are very common in PDA seial cables also, but can be purchased from Compsys Bench

Item Name: A232DBH3v Max232 3.3v ver. adapter assembled w/hood kit 
Item Number: A232DBH3v 

SuperDroid Robots (#MCU-026-172) or CompSys (#A232DBH3v).


As an alternative you can make the level shifter cable yourself: Circuit Console Cable.pdf (courtesy Type-G). Components can be found at e.g. Digikey

  • If you want to build your own serial converter, you will need the following parts:
  • (5) 0.1 uF resin dipped capacitors (Monroes), 16V
  • (1) MAX3232CPE IC (Maxim), 3V type, 16 pin DIL
  • (1) Right angled RS232 male socket
  • (1) 10 element stripboard
  • (1) 16 pin chip mount
  • (1) Wire


You can also etch a circuit board which makes building th einterface and installing the interface really easy. Instructions are Here.

This should be attached as close as possible to the board. The signals are very weak and wires as short as 2" (5 cm) have been reported to cause data loss across the serial port.

See Also

Stage 5 - Cleaning Up

TO BE COMPLETED


Stage 6 - Using the Serial Console

  • You may access the serial console using Windows HyperTerminal (included with Windows) or [TeraTerm Pro].

Serial Port Settings

Data Settings 
Baudrate  57600
Data bits  8
Stop bits  1
Parity  None
Flow Control  None