Serial Link Box

I made the "Serial Link Box" for people who own a serial null modem cable. It's based of the serial link developed by Tobin Fricke and Timo Stenberg, and should be compatable with any serial cable program. I recommend Sami Khawam's transfer programs, which are availiable at http://sami.ticalc.org/tran8/. Any questions, comments, etc. email me at moose1@delanet.com. If anyone makes this link box please email me and tell me how it goes.

link box schematic

(invert to print) (sorry about the poor quality, I used a Barbie digital camera)

Materials:

From Radio Shack:

1 pack 3.3k ohm 1/2 watt resistors
1 pack 330 ohm 1/2 watt resistors
1 pack >= 4.7k ohm 1/2 watt resisters
1 card 4.7 or 5.1v Zener Diodes
2 packs Surface mount LEDs (1 red, 1 green)
1 card Male 9-pin RS-232 connector
1 Project box with PC solder board

From Mouser:

1 Stereo 2.5 mm phono jack (stock # 161-3307)
I recommend putting it together on a breadboard first to ensure it works correctly. You should use a multimeter to check the voltage coming from the 2.5mm jack. Before the port is activated it should read about -.5 to -1 volts and after between 4 and 5 volts DC. After you tranfer a few things to make sure its working get the box and drill 4 holes in it. 3 on top for the LEDs and one on the front for the 2.5mm jack. Its about a 1/4 inch hole but use 3/8 or so that way you don't make them too big. The Male 9-pin jack is more difficult. I just used a razor and cut out a square in the box big enough that it would just barely fit then screwed it in with small sheet metal screws. Then solder it all together on the PC board and mount the jacks and LEDs. I used solid phone wire to connect every thing. It's stiff and easier to use, just make sure you solder everything good. Plug in your null modem cable into a COM port, plug your serial link box into the other end of the null modem cable, plug your TI-TI link that came with your calculator into the box and the other end into your TI-calc and your ready to go.