uP infra-red interface - transmits serial computer information

july/august 1984 transmits serial computer information In general the normal connections between a computer and its peripherals are very effective but these cables could hardly be con- sidered decorative. A cable carrying serial information can, however, be replaced by this infra-red interface even though it only consists of a simple transmitter and receiver. As figure 1 shows, the transmitter uses a single BC 557B transistor to drive the infra-red LED. The transistor is itself controlled by the micro- processor so a short program is required to make the computer generate the transmitter signals needed. The frequencies used here are 4800 and 9600 Hz and the maxi- mum baud rate at these frequencies; is 1200 baud. The receiver, seen in figure 2, makes use of an IC (the SL486) especially developed for infra-red applications. This contains several gain stages, a pulse-width expander, and a voltage regulator. The receiver diode (Dl) is connected directly to the IC. The stretch output, ...