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
OUT 888,(12 +16*14)