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PC or PICAXE interface for UHF remote control

Simple circuit lets you control the Oatley Electronics 4-Channel UHF Transmitter using a PC or PICAXE

By John Holliday

Click for larger image
The Oatley Electronics 4-channel UHF transmitter board includes an SM5023 trinary encoder IC and a pre-built UHF transmitter module (mounted on the underside of the board).

THE ORIGINAL Oatley Electronics 4-channel UHF transmitter board had manual pushbuttons but these can be omitted for computer control. In fact, one transmitter can control the four channels on up to 16 separate remote receivers – that’s up to 64 computer channels altogether!

This circuit concept uses the eight data lines from a PICAXE18A or the parallel printer port of any PC. Since the PC situation is the more complex, I will limit the article to describing how to interface the parallel printer port of a PC to the transmitter. I will assume the reader is familiar with the article in the June 2003 issue.

Table 1: QBASIC Code

lowernibble = 12 'set variable "lowernibble" to required receiver code
channels = 14 'set variable "channels" to required channel combination
uppernibble = 16 * channels 'put channel combination into the upper nibble
outputdata = lowernibble + uppernibble 'combine the two nibbles
OUT 888,outputdata 'put the data on the data lines D0-D7 (LPT1)

Once you know what you are doing, the above lines can be condensed into one:

OUT 888,(12 +16*14)

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