2021-01-29 06:31:58 -05:00
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[](https://github.com/marketplace/actions/arduino_ci)
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2021-12-22 06:10:05 -05:00
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[](https://github.com/RobTillaart/MultiMap/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MultiMap/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MultiMap/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MultiMap/releases)
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2021-12-22 06:10:05 -05:00
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2020-11-27 05:20:37 -05:00
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# MultiMap
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Arduino library for fast non-linear mapping or interpolation of values
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2021-05-28 07:39:42 -04:00
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2020-11-27 05:20:37 -05:00
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## Description
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In Arduino applications often the value of a sensor is mapped upon a more
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usable value. E.g. the value of analogRead() is mapped onto 0 .. 5.0 Volt.
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This is done by the map function which does a linear interpolation.
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This means in code:
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```cpp
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output = C1 + input * C2
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```
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As C1 and C2 are to be calculated Arduino has the **map()** that calculates the
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two variables runtime from two given mappings.
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```cpp
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output = map(input, I1, I2, O1, O2):
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```
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In many cases when there is no linear mapping possible, as the 'points' are not on a single straight line.
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One needs non-linear math to calculate the output, **Multimap()** just simulates that.
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**out = Multimap(value, input, output, size)** needs two equal sized arrays of reference 'points',
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**input\[\]** and **output\[\]**, it looks up the
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input value in the input\[\] array and if needed it linear interpolates between two
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points of the output\[\] array.
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- The **input\[\]** array must have increasing values,
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there is no such restriction for the **output\[\]** array.
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- **Multimap()** automatically constrains the output to the first and last value in the **output\[\]** array.
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## Operation
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See examples
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Please note the fail example as this shows that in the intern math overflow can happen.
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## Future
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2022-11-18 09:09:05 -05:00
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#### must
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- improve documentation
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#### should
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- Investigate class implementation
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- performance / footprint
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- less parameter passing
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#### could
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- flag if input value was "IN_MIN" < input < "IN_MAX",
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now it is constrained without user being informed.
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- extend unit tests
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#### wont
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- should the lookup tables be merged into one array of pairs?
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- you cannot reuse e.g. the input array then. (memory footprint)
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