Arduino programming guide series
08
The Arduino "map" function
The map() function makes it easy to convert numbers from one range to another. Here's a simple example of its usage.
The map() function makes it easy to convert a value from one range into a proportional value of another range.
Let’s use an example that involves a potentiometer and an electrical motor.
We can sample the potentiometer with one of Arduino’s analog inputs, which have a resolution of 1024 values (10 bits). For this purpose, we use the analogRead() function.
To control the motor, we use Pulse Width Modulation which has a resolution of 256 values (8 bits). For this purpose, we use the analogWrite() function.
Therefore, whichever value we measure in the analog inputs, we have to convert it to a proportional value inside the PWM range of values.
Using the map function, this is as simple as this:
int mappedVal = map(analogRead(0),0,1023,0,254);
Say that the analogRead() function read the value "328" from the potentiometer. The call to the map() function will look like this (I have replaced the call to analogRead() with the explicit value "328"):
int mappedVal = map(328,0,1023,0,253);
The result of the mapping will be 81, which will be stored in the mappedVal variable.
Would you like to try this yourself? Here's my Tinkercad project. It contains a virtual Arduino Uno with a simple sketch that contains the map() function example.
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10. The interrupt service routine and volatile variables
11. The problem with delay() and how to fix it
12. How to deal with the millis rollover
13. Can you use delay() inside Interrupt Service Routine?
15. A closer look at line feeds and carriage returns
16. Understanding references and pointers
17. Simple multitasking on the Arduino
19. Concurrency with the Scheduler library on the Arduino Due and Zero
20. Bitshift and bitwise OR operators
21. What is a "static" variable and how to use it
22. Understanding the volatile modifier
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