Microcontroller inputs parallel data using one pin

摘要

Inputting multiple bits of information using a single entryrnpin of a microcontroller without the complexity of UARTs can prove useful. Such a scheme could allow scanning of a keyboard, mode switches, or any relatively slowly changing digital data. Reference 1 details arntechnique for outputting signals with a single pin. The data from switch bank S_1 first presents itself to IC_3, a 74HC165 parallel-to-serial converter from NXP Semiconductors. Loading the data into the shift register requires a pulse on the PL line (Pin 1). Line CKrnaccomplishes this pulse by sending as output a long pulse on the microcontroller-pin line. R_2 and C_2 introduce a delay, and, once the pulse exceeds that delay, the PL line goes low, and the data loads.