Bit banging is a technique for serial communications using software instead of dedicated hardware. Software directly sets and samples the state of pins on the microcontroller, and is responsible for all parameters of the signal: timing, levels, synchronization, etc. In contrast to bit banging, dedicated hardware (such as a modem, UART, or shift register) handles these parameters and provides a (buffered) data interface in other systems, so software is not required to perform signal demodulation. Bit banging can be implemented at very low cost, and is used in, for example, embedded systems.^[1]

Although it is often considered to be something of a hack, bit banging does allow the same device to use different protocols with minimal or no hardware changes required.

There are some problems with bit banging. The software emulation process consumes more processing power than does supporting dedicated hardware. The microcontroller spends much of its time reading or sending samples to and from the pin, at the expense of other tasks. The signal produced normally has more jitter or glitches, especially if the processor is also executing other tasks while communicating. However, if the bit-banging software is interrupt-driven by the signal, this may be of minor importance, especially if control signals such as RTS, CTS or DCD are available.

C code example

See also

• Bit manipulation
• Bit twiddler

References

External links

Asynchronous Serial (RS-232)

• Notes on bit-banging async serial
• Bit banging for Async Serial Communication
• Bit banging for RS-232

I2C Bus

• I2C on AVR using bit banging

SPI Bus

• Efficient bit-banged SPI for 8051 microcontroller

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