5.6 Map

If you observe carefully, you will notice that many values have different ranges in programming. For example, the range of values for analog inputs is (0~1023). The value range for the analog output is (0~255). The output angle of the servo is (0~180).

This means that if we want to use the potentiometer to control the brightness of the LED or the angle of the servo, we need to go through a mapping operation.

Now let’s see how to achieve it.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

3 in 1 Starter Kit

380+

3 in 1 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

SunFounder R3 Board

BUY

Breadboard

BUY

Jumper Wires

BUY

Servo

BUY

Potentiometer

BUY

Schematic

../_images/circuit_8.3_amp.png

Wiring

../_images/map_bb.jpg

Code

Note

  • Open the 5.6.map.ino file under the path of 3in1-kit\basic_project\5.6.map.

  • Or copy this code into Arduino IDE.

  • Or upload the code through the Arduino Web Editor.

After the code is uploaded successfully, you can rotate the potentiometer back and forth, and the output shaft of the servo will rotate back and forth.

How it works?

map(value, fromLow, fromHigh, toLow, toHigh): Map a number from one range to another. That is, a fromLow value is mapped to toLow, and a fromHigh value is mapped to toHigh.

Syntax

map(value, fromLow, fromHigh, toLow, toHigh)

Parameters

  • value: the number to map.

  • fromLow: the lower bound of the value’s current range.

  • fromHigh: the upper bound of the value’s curr+ent range.

  • toLow: the lower bound of the value’s target range.

  • toHigh: the upper bound of the value’s target range.

If the potentiometer controls the LED, you can also use the map to complete the task.

int x = analogRead(knob);
int y = map(x,0,1023,0,255);
analogWrite(led,y);

Notes and Warnings

  • The “lower bound” of both ranges may be larger or smaller than the “upper bound”, which means that the map() function can be used to reverse a range of numbers.

    y = map(x,0,180,180,0);

  • Mapping also works well for negative numbers.

    y = map(x,0,1023,-90,90);

  • The mapping uses integers, and the decimal places of floats are discarded.