Page 86 - Programming the Photon Getting Started With the Internet of Things

lcd.begin(16,2);

After this setup procedure you can now call the functions print() and setCursor()
commands to print any given text to any particular place on the LCD display. The
positions on the screen are indexed starting with (0,0) in the top left of the screen. The first

argument setCursor() specifies the column number, and the second specifies the row
number. By default, the starting location is always (0,0). So if you call the first command
print() without first changing the cursor position, it will print starting in the top-left

corner.

NOTE The library does not check to see if the text you are printing fits in the display, so
make sure your text is within the 16-character limit.

This experiment is a great example of how to display information using an LCD
display. The display can also show information from sensors, such as temperature and

humidity, as well as date and time stamps. You should now be able to experiment with
displaying other information.

Analog Outputs

Now that we have looked at digital output controls, it is time to understand a bit about the
analog pins on the Photon board. Although controlling digital components is good, what if
we wanted to control them with a bit more precision, such as the brightness of an LED or
the speed of a motor? Well, you can’t normally do this using a digital system, but there is a
way using a simple digital-to-analog convertor (DAC) chip and using something called

pulse width modulation (PWM).

Pulse Width Modulation

First let’s take a look at using PWM, which is commonly found on most single-board

computing devices such as the Photon. This method allows you to get pretty close to
generating analog values by emulating what an analog signal should be like. On the
Photon board five analog pins are available, which all generate PWM signals—these pins

are labeled A0–A5.

Let’s go back to our first experiment in this chapter where we flashed an LED on and
off. We will use that same circuit, but instead of connecting the LED to digital pin D0, we
can connect it to pin A0 as shown in the breadboard layout diagram in Figure 4.8.