map2bits

Arduino library for mapping a float to a number of bits.

Description

Map2bits is an experimental library which can be used to map a float value to a number of HIGH bits in an 32 bits integer.. The float value can be the result of a calculation or measurement from a sensor, e.g. temperature, humidity, light, distance, direction or pressure.

map2bits is developed to drive a led bar like this one. https://www.tinytronics.nl/shop/nl/displays/segmenten/led-bar-10x-rood typical in combination with a PCF8575 or a MCP23017. These are used for displaying e.g. audio volume, current level, temperature etc in a visual way.

Another application might be to control multiple pumps in a row to pump water from a pit. Depending on the level of the water more pumps need to be switched on.

In short many devices to drive or applications to think of.

As always, feedback is welcome.

Related

Other mapping libraries

• https://github.com/RobTillaart/FastMap
• https://github.com/RobTillaart/Gamma
• https://github.com/RobTillaart/map2bits
• https://github.com/RobTillaart/map2colour
• https://github.com/RobTillaart/moduloMap
• https://github.com/RobTillaart/MultiMap

Interface

#include "map2bits.h"

Functions

• map2bits() Constructor, defines a default mapping of (0..100 => 10)
• uint8_t init(float in_min, float in_max, uint32_t bits) defines the mapping input range and how many bits output should be generated.
• uint32_t map(float value) maps value to an uint32_t with the appropriate number of bits set. These are constrained by the number of bits set in init().

The output of map() is a bit mask and can be used to drive e.g. a led bar etc.

Operation

Suppose you have the following code

mb.init(0, 100, 10);
                       //      (binary)
x = mb.map(64);        //  x =     111111 ==>  6 bits set, interpolated
x = mb.map(99);        //  x = 1111111111 ==> 10 bits set, interpolated
x = mb.map(4);         //  x =          0 ==>  0 bits set, interpolated
x = mb.map(-10);       //  x =          0 ==>  0 bits set, constrained
x = mb.map(1000);      //  x = 1111111111 ==> 10 bits set, constrained

See examples.

Performance

Indicative performance measured with the map2bits_performance.ino example. Performance depends on input chosen, platform support of float, and if values are constrained (out range) or interpolated (in range)

Note: time in microseconds per call Note: UNO at 16 MHz, ESP32 at 240 MHz

board	map - in range	map - out range	notes
UNO	45.35 us	22.20 us	33% in range, 66% out range
ESP32			to do

Future

Must

• update documentation
• test ESP32

Should

• extend the idea to applications
• add examples
• optimize

Could

• test other boards
• map2bits64(value) uint64_t for 33 - 64 bits output
  • might need printHelpers
• map2bitsDouble(value) Double version (input range + precision)
• map2bitsDouble64(value) Double version (33 - 64 bits output)
• uint32_t input version
• map2DAC?
  • maps a range to analogWrite()..
  • separate class.
• polarity 0001 <> 1110 ?
  • ~operator
• MSB/LSB 0001 <> 1000 ?
  • reverse from CRC library

Wont

Support

If you appreciate my libraries, you can support the development and maintenance. Improve the quality of the libraries by providing issues and Pull Requests, or donate through PayPal or GitHub sponsors.

Thank you,