Difference between revisions of "Add Serial Port"

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Revision as of 21:28, 27 March 2006

How to attach a serial port to the Kurbox/KuroboxHG

 Please note the adding of a serial port requires soldering onto the main board of the Kurobox and can cause catastrophic failure to the hardware. You have been warned 

Locate J1 on the Mainboard after removing it from the case. This should be a 4 pin unpopulated header. To allow one-way serial port traffic (read only) you can just add the 4 pin header and be done. To enable bi-directional serial port activity, you must also add a 10K resistor as described below.

Enabling Write support (optional)

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.  


Adding the serial port

J1 Pinout
Pin  Signal
1 Transmit (TX)
2 Receive (RX)
3 Power (3.3V)*
4 Ground (GND)


Adding the level shifter

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 

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


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


If you use the Compsys level shifter you should remove the 9 pin D connector from the shifter and solder the transmit and receive pins directly to the new header. this makes the shifter sit directly above the circuit board and makes the wires as short as possible. you will need to use 2 short (about 3/4") pieces of wire to connect the power and ground connections on the level shifter to the header. next you should connect 6" pieces of wire to the transmit, receive and ground connections on the rs232 side of the level shifter and route them to the 9 pin D connector which can be mounted on the rear of the kurobox.


Once you have the level shifter installed you should be able to see console messages via the serial port.


Serial Port Settings

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