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66 lines
2.2 KiB
Markdown
66 lines
2.2 KiB
Markdown
---
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title: Mapping Values
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---
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# #13. Mapping Values
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<div class="ui segment note">
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<span class="ui ribbon label">Note</span>
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This is a web-version of a tutorial chapter embedded right into the XOD IDE.
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To get a better learning experience we recommend to install the
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<a href="/downloads/">desktop IDE</a> or start the
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<a href="/ide/">browser-based IDE</a>, and you’ll see the same tutorial there.
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</div>
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If you have read the documentation page of the thermometer node, you will have
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noticed that it provides an output temperature value to the `Tc` pin in degrees
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Celsius. If we’re going to show the temperature with an arrow driven by a servo,
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we’re in trouble. The `servo` node can work only with values ranging from 0 to
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1 (0 is 0°, 1 is 180°).
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The practical task is to make the servo rotate smoothly from 0 to 90°,
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reflecting a temperature change from 20°C to 50°C.
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You can actually do this using few math nodes, but XOD has a special node for
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such cases. This node is called the `map` node.
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The node has pins:
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* `X` — the input value that needs to be transformed;
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* `Smin` — the lower bound of the input range;
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* `Smax` — the upper bound of the input range;
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* `Tmin` — the lower bound of the transformed value;
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* `Tmax` — the upper bound of the transformed value;
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* `Xm` — the mapped (transformed) value.
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Setting them properly would map an input from one range to an output in another.
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## Test circuit
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<div class="ui segment note">
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<span class="ui ribbon label">Note</span>
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The circuit is the same as for the previous lesson.
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</div>
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[↓ Download as a Fritzing project](./circuit.fzz)
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## How-to
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1. Add the `xod/math/map` node to your patch.
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2. Link the `X` input to a value to be mapped.
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3. Set input (source) range bounds with `Smin` and `Smax` (e.g. 20 and 50).
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4. Set output (target) range bounds with `Tmin` and `Tmax` (e.g. 0 and 0.5).
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5. Use `Xm` as the resulting value in the new range.
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If you followed the example try to heat the thermometer with a hot object (i.e.
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a paper knife heated with a lighfire). At a temperature of 35°C (half the input
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range), the servo should rotate to 45°, which is half the output range.
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[Next lesson →](../14-map-adjust/)
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