HackSpace_-_October_2019

FORGE

has a Serial Plotter that converts numbers sent over
a serial connection into a graph.
The Serial.println() function can take a few
different data types, including floats (as shown here)
and strings.
This is a great way of seeing what’s going on in
your scripts, but it can also be used to send data to
programs running on your PC. Most programming
languages have a library or module for working with
serial connections, so you can send data directly
from your microcontroller to software running on
your PC.

BACK AND FORTH
So far we’ve seen data sent from the microcontroller
to the computer, but the serial protocol is
bidirectional (well, really, it’s two unidirectional
channels pointing in opposite directions, but let’s not
worry about that), which means we can also send
data from our computer to the microcontroller. The
following code (which you’ll find in your Arduino IDE
in Examples > Communication > Dimmer) takes data
in and uses it to control the brightness of an LED.

const int ledPin = 13;

void setup() {

Serial.begin(9600);

pinMode(ledPin, OUTPUT);

}

void loop() {

byte brightness;

if (Serial.available()) {

brightness = Serial.read();

Serial.println(brightness);

analogWrite(ledPin, brightness);

}

}

While Serial.println() can take a wide variety of

formats, Serial.read() will always return a single

one-byte character. In this case, we’re using this to

control the brightness of the LED. However, by

default, the serial monitor will also send characters

for line end and carriage return, so we need to turn

these off. Change ‘Both NL and CR’ to ‘No Line

Endings’. Now, when you enter a character into the

box and hit Send, the LED will be adjusted based on

the ASCII value for that character. With letters, ‘A’ is

the lowest and ‘Z’ is the highest brightness.

Because of the one byte limitation, it’s easiest if

you can limit data sent from your computer to your

microcontroller to single bytes. Commands can be

single letters, etc. However, if this isn’t possible, you

can build up data by reading multiple bytes (i.e.

calling Serial.read() several times) and stitching the

data together in the way you need.

Using serial, you can quickly and easily create

custom USB gadgets for your computer, or send

data back and forward to control your makes.

Above

Serial can send data

in both directions

Here, we’ve looked at how to connect a computer to

a microcontroller and communicate via USB serial,

but there are loads of other devices that you can link

your microcontroller to via serial. One popular option

is Bluetooth serial links. These are hardware devices

that expose a Bluetooth connection as a serial port.

Any data you send down the wired serial link between

the microcontroller and Bluetooth module will be sent

over the Bluetooth link to whatever the module is

paired with. You can use this to send data back and

forth between your microcontroller and mobile phone

(there are several Bluetooth serial apps available), or

other Bluetooth-enabled devices.

NOT JUST COMPUTERS