Single-board microcontroller: Difference between revisions

Revision as of 17:33, 12 May 2020

Revision as of 16:31, 27 May 2020

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Discrete digital inputs and outputs might be buffered from the microprocessor data bus only by an addressable latch, or might be operated by a specialized input/output IC, such as an [[Intel 8255]] or Motorola 6821 [[Peripheral Interface Adapter|parallel input/output adapter]]. Later single-chip microcontrollers have input and output pins available. These input/output circuits usually do not provide enough current to directly operate devices like lamps or motors, so solid-state relays are operated by the microcontroller digital outputs, and inputs are isolated by [[signal conditioning]] level-shifting and protection circuits.

One or more analog inputs, with an analog multiplexer and common [[analog -to -digital converter]], are found on some microcontroller boards. Analog outputs may use a digital-to-analog converter or, on some microcontrollers, may be controlled by [[pulse-width modulation]]. For discrete inputs, external circuits may be required to scale inputs, or to provide functions like [[Wheatstone bridge|bridge]] excitation or [[cold junction compensation]].

To control component costs, many boards were designed with extra hardware interface circuits but without the components for these circuits installed, leaving the board bare. The circuit was added as an option on delivery, or could be populated later.