U-OFA-URC: Serial Port Cable

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What is It?

This special cable is required to provide level shifting between serial port (RS232) logic levels and One-For-All (CMOS) logic levels.

You will also need to aquire or build software to send the correct signals out the serial port. The document http://www.John-Wasser.com/OFA/SerialSoftware.html covers both where you can buy OFA control software and where to find the data that will allow you to write your own.

Where can I Buy One?

You used to be able to buy the cable from Home Automation Systems (http://www.smarthome.com/) but they seem to have stopped carying it as a separate item. It might come bundled with the IRDC software that they still sell since the software is useless without the cable. You can get their catalog by sending your full mailing address to catalog@smarthome.com or by calling them at 800-SMART-HOME (800-762-7846).

How can I Build One?

This design is by Jim Griggers (jdg@devine.ColumbiaSC.NCR.COM) and was posted by Robert Rolf (then rrolf@gpu5.srv.ualberta.ca, now Robert.Rolf@UAlberta.ca) who has done a different design (using a 74HC14) which we will hopefully see later.

    IBM
    DB9F DB25F                                         OFA Remote
Tx   3    2  ---/\/\/\/-------------------+------------ 1 (from PC)
                 1K                       |
                                 +--->|---+  <--1N4148 or 1N914 etc
                                 |         
Gnd  5    7  --------------------+--------------------- 2 (Gnd)
                                 |
                                 +-(E   
                                    B)-----/\/\/\/----- 3 (To PC)
Rx   2    3  --------------+-------(C         10K
                           |      2N3904
                           |        or 
DTR  4    20 --+           |      2N4401
 or             --/\/\/\/--+
RTS  7     4 --+    4.7K
(pick one)

DTR (or RTS) provides power and must be turned on (+12V) for circuit to work. For a Macintosh 8-pin DIN connector, use pin 3 for Tx, pin 4 for Gnd, pin 5 for Rx and pins 1 and 2 (HSK0 and HSK1) tied together for power (DTR/RTS).

You can also find a similar diagram in JPEG form at Zig's Amazing IR Remote Control Page.

The connection holes in the remote are not usualy numbered. The above numbering is arbitrary and may not match whatever labels are provided. Below is a table that shows the order of numbering when looking into the battery compartment with the remote pointed upward:

URC-2005 One For All 5 "Upgradable": Left to Right
URC-2093 One For All 3 "One Call 3": Unknown (horizontal)
URC-2094 One For All 4 "One Call 4": Unknown (horizontal)
URC-4000 One For All 6 :Unknown
URC-4005 One For All 6 "Upgradable": Left to Right (labeled "RX", blank, and "TX")
URC-4050 One For All 6 Hi-Fi "Upgradable": Left to Right
URC-5000 One For All 12: Right to Left
URC-6050 One For All 8 Hi-Fi "Upgradable": Unknown (horizontal)
URC-6800 One For All "VCR Pro 8": Unknown
URC-6885 One For All "VCR Pro 4": Unknown (vertical) 6 upgradable
URC-4300 One For All 6 "Upgradable" (UK only?): Left to Right (labeled "3", blank, and "1")

If you know the answer to any of the unknowns above, please send me mail at U_OFA_URC@John-Wasser.com.