Each Arduino attaches to a specific com port. The port may have to be changed or selected in the tools tab under “port” to get the IDE to recognize the Arduino.

If the code is being pasted into the IDE, do not copy from Microsoft Word or another word processor. First, put it in a text editor such as Notepad, Notepad++, or some other C/C++ IDE editor and then copy it from there. Important note: Notepad and Notepad++ are not development tools like the IDE. One other very important item of note is when the code was transcribed into the book format some of the code text that must be on one line may show up on two lines in this book. The authors have tried their best to highlight the code that should be on one line in the IDE by bolding it in the Listing. Please contact the authors if there are questions at [email protected].

It is a good idea to test the devices with a basic program to be sure they work, before moving to a more complex program.

If the final code is complex, get each piece of code working before adding more modules. This way, it is easier to find the module where the problem is located.

The authors recommend for long timing events or complex programs to not use the “delay command,” because it locks the Arduino and prevents it from doing anything else. Instead, use the “milli command” that tracks time intervals between events and still allows other actions to occur. The milli code might be a little more complex, but it allows the Arduino to perform other functions simultaneously. Using the delay command for short events or simple programs like the ones in this book, such as a switch debounce, is recommended.

A feature built into the Arduino IDE is the “auto-format command.” It can be found under the tools tab or using “Alt+T.” This command helps identify missing items and also helps organize the code for improved readability.

One more key aspect of Arduino coding is the “loop command.” There are a few different types, but common ones such as “void loop” and the “for command” perform several operations and then repeat them.

Check the wiring twice before applying power. It can be difficult to see which port a wire is plugged into when there are several wires.

It is hard to know what code is on an Arduino. One easy way that helps determine what is loaded on an Arduino is saving code with a descriptive name, date, and even time information. This helps programmers who may need to go back to a previous code version.

One other very helpful trick is to put the descriptive name of the code on a piece of tape and stick it on top of the computer port. This helps when working on, or programing, several different Arduinos.

One of the advantages of the Arduino is that once it is programmed, it remembers the code. When a power source is plugged into the battery power port, it will operate the Arduino. According to the Arduino web site, any power source that can supply 9–12 V DC, 250 mA, or more will work. The plug must be 2.1 mm with the center pin providing positive voltage and the exterior of the plug the negative terminal. Some power supplies do not deliver enough current or do not provide stable power. If an Arduino is behaving strangely, try a different power supply.

Some programs need special ways to use and communicate with the Arduino. To do this, the reader should understand these special connection ports on the Arduino Uno: analog A5 is the SCL (Clock port) and A4 is the SDA (Data port).

Keyboard configuration: The reader may find when they first start out and type a command in on the keyboard that the wrong character may show up on the screen. In the authors’ case, the Raspberry Pi 3 was configured for a keyboard in a different country. To fix this, the reader should visit the Stack Exchange site as most likely the keyboard is set for a UK version. US or other countries’ keyboards have a slightly different mapping arrangement.

This site has more info on this change: https://​raspberrypi.​stackexchange.​com/​questions/​236/​simple-keyboard-configuration.

An important lesson the authors learned is that the Raspberry Pi 3 power supply needs to deliver the correct amount of current required. The authors needed two power supplies: one for the touchscreen and one for the Raspberry Pi. The touchscreen power supply did not put out enough current for the Raspberry Pi and caused it to crash often.

Timing issue: You may notice that if you want precision control of timing, the Raspberry Pi program may be off by a few milliseconds. This is partially due to Raspberry Pi not being a real-time system and partially due to Raspberry Pi’s Linux-derived operating system (OS) overhead. You can find many examples of real-time systems in the real world. One example of a real-time system is how a microwave, when the door is opened, immediately shuts off so that the person operating it is not exposed to harmful microwaves. Real-time systems have to be able to react rapidly to interrupts. This is different from a personal computer, generally known as general-purpose system, an OS where interrupts don’t take priority due to how the chipset is designed. General-purpose systems provide multiple functions which take some minimum amount of time to execute. All general-purpose OSs have some form of overhead that comes in various forms from longer boot-up time to latency between receiving an interrupt event for a new unscheduled task. The Arduino operates closer to real time, so if the reader needs to know the time data is taken, then they might want to consider using the Arduino instead of the Raspberry Pi.

One other key difference between the Raspberry Pi and the Arduino is the voltage needed to power them. The Raspberry Pi uses 5 V DC. The Arduino can use 9–12 V DC. It is critical not to use a power supply meant for an Arduino on a Raspberry Pi; it will damage it.

Unlike the Arduino, the Raspberry Pi does not have a built-in analog to digital converter. Therefore, when using analog sensors, the reader may need to place an analog to digital converter between the sensor and the Raspberry Pi.

Many Raspberry PI programs use modules. Some of these modules are included in the Python code like Tkinter. This is used in the astrophotography project. Other modules are not included, in particular, Adafruit_GPIO.SPI and Adafruit_MCP3008, which are used in several projects in this book.

When installing modules like Adafruit_GPIO.SPI and Adafruit_MCP3008, the user must ensure they are installed in the correct folder. Use pip3 or pip2 depending on the version of Python on the Raspberry Pi.

The Raspberry Pi may come with an SD card with the operating system. However, the reader may download the operating system and install it on an SD card. When formatting an SD card for the Raspberry Pi operating system, run the Guiformat program to create an exFAT (also known as 32-bit FAT) SD card and leave all options at default. This web site has some helpful info:

www.raspberrypi.org/documentation/installation/sdxc_formatting.md.

Finally, the authors used two different programming tools on the Raspberry Pi. They are Python3 and Thonny. They seem to behave very similar and have very similar graphical user interfaces.