Arduino Sketches. Langbridge James A.

digital inputs/outputs and 6 analog inputs. It has a JST battery power connector, a power switch to select between power modes, and space reserved for a power jack, if needed. It does not have a USB connector but instead uses a FTDI cable for programming.

The Arduino Pro is different from most other Arduinos in that while it is a prototyping board it is designed to be embedded in projects. It does not come with headers – indeed, it does not have any headers at all, as shown in Figure 1.11. All the digital and analog inputs and outputs are placed at the exterior of the board, retaining shield layout, ready to be soldered to wire or connectors if necessary. Instead of being used for prototyping, the Arduino Pro is aimed at semipermanent installation in finished products. The Arduino Pro was not designed by Arduino but was designed and is manufactured by SparkFun Electronics.

Figure 1.11 The Arduino Pro

      Arduino Robot

      The Arduino Robot is, simply put, an Arduino on wheels. There are two Arduino boards on the Robot – one controls the on-board motors, and the other contains sensors. The Control board controls the Motor board and gives it instructions on how to operate.

      The Control board is powered by an ATmega32u4, with 32 KB of flash, 2.5 KB of SRAM, and 1 KB of EEPROM. It also has an external I2C EEPROM device, providing more storage. It has a compass, a speaker, three LEDs, a five-button key pad, and an LCD screen. It also has three solder points for external I2C devices. It also has I/O capability, with five digital I/Os, six PWMs, and four analog inputs. There is space for eight analog inputs (for distance sensors, ultrasound sensors, or other sensors) and six digital I/O pins for other devices (four of which can be used for analog input).

The Motor board is a fully independent board, powered by an ATmega32u4, the same microcontroller as on the Control board. The Motor board contains two wheels powered independently, five IR sensors, and I2C and SPI ports. It also contains the power supply; it is powered by four rechargeable AA batteries, and contains a jack port to recharge the on-board batteries. The board can also be powered by an on-board USB connector, but in this configuration, for safety reasons, the motors are disabled (Figure 1.12).

Figure 1.12 The Arduino Robot

      Arduino Esplora

      The Arduino Esplora is a strange device. Where most Arduinos are designed to sit on a table or be placed under fabric, the Esplora is designed to be held in your hand. Based on an ATmega32u4, it is not shield compatible and does not have any solder points for inputs and outputs. Instead, it looks and feels like a game pad; it has thumb inputs in the form of four digital switches, one analog joystick, and a linear potentiometer. For more feedback, the Esplora has a buzzer and an RGB LED. It also features more advanced devices; it has an on-board microphone, a temperature sensor, a connector for an LCD screen, and a three-axis accelerometer.

The Esplora has 32 KB of flash; 4 KB are used by the bootloader. It has 2.5 KB of SRAM, and 1 KB of EEPROM. It is a capable device, and it makes up for its lack of connectors with four TinkerKit connectors: two inputs and two outputs, as shown in Figure 1.13.

Figure 1.13 The Arduino Esplora

      Arduino Yún

      The Arduino Yún is based on an ATmega32u4, but it also has an Atheros AR9331 on the same board. The Atheros processor has a complete Linux distribution, based on OpenWRT, famous for Linux-based wireless routers.

The Arduino Yún has built-in Ethernet and WiFi, and also has a micro-SD slot. The Yún is different from other Arduinos and shields in that it has advanced network functionality; the Arduino can send commands to OpenWRT and then continue processing its sketch (Figure 1.14). The two processors work independently, the Bridge library facilitates communication between the two processors.

Figure 1.14 The Arduino Yún

      Arduino Tre

      The not-yet-released Arduino Tre promises to be a phenomenal beast. Up until now, the fastest Arduino was the Arduino Due, based on an ARM-compatible microcontroller. The Tre, created by Arduino and BeagleBoard, combines the power of a full computer with the flexible input and output of an Arduino.

      The Tre has a Cortex-A8 class processor, the Sitara AM335X processor, running at 1 GHz. This processor has access to 512 MB of RAM and has an HDMI port capable of displaying Full HD (1920 x 1080). All this power is interfaced by an Atmel ATmega32u4 using the Arduino programming environment that enthusiasts have come to love.

      Arduino Zero

      The Arduino Zero is a brand new Arduino using Atmel's SAM D21 microcontroller. It has 256 KB of flash memory, 32 KB of RAM, and runs at 48 MHz. The Arduino Zero is designed to handle future requirements from the Maker community, by creating a design that is powerful, robust, and flexible enough to be used in robotics and wearable projects, as well as the IoT. It is also the first design to have an advanced debugger interface.

      Your Own Arduino?

      Arduino has always created open-source designs, and all the boards listed previously have schematic files available directly from the Arduino website, under a Creative Commons Attribution Share-Alike license. Put simply, this means that you are free to study the Arduino schematics to make your own or to make modifications either for personal use or professional use on the condition that you give credit to Arduino for the original design and release your own design under the same license.

      With the exception of the Arduino Due, all Arduino boards are based on the Atmel AVR. These chips can be bought from electronic distributors with the Arduino firmware pre-installed, or if you have the proper tools, you can buy blank chips and load the firmware yourself.

      Shields

      An Arduino by itself is a capable device and already includes numerous input and outputs, but its power only starts there. Because Arduino designs are open source, numerous companies have developed shields, printed circuit boards that are placed on top of the Arduino board that connect to the Arduino's pins. There shields add functionality by using different inputs and outputs, either digital I/O or through serial communication.

      What Is a Shield?

      A shield is a printed circuit board that can be placed on the top of most Arduino boards. It connects to the Arduino's processor through male header pins. Adding a shield to an Arduino does not necessarily expand the possibilities of an Arduino, but most do.

      For most prototyping projects, you connect wires to the Arduino's headers and connect them to a breadboard. This is easy enough for a lot of applications, like outputting data to two or three LEDs. For more complex applications, a breadboard isn't practical due to the complexity of the wiring, or the size of the components. Micro-SD card readers are extremely small and cannot be placed onto a breadboard. Soldering wires to a micro-SD reader isn't particularly easy, so your choices are limited. Writing data to a micro-SD card is something that can happen a lot, so it's fortunate several companies have developed shields with a micro-SD reader. If your application requires data logging, all you have to do is to connect the shield to the top of the Arduino, add a few lines of code, and you are ready to go. It is that simple.

      As said previously, not all shields add functionality. Some shields exist to help prototyping – allowing you to solder components onto the shield – without having to make your own PCB. Prototyping on a breadboard is an excellent way to test that your design works, but after the design is proven, it is time to make a better board. For example, if you were creating a doorbell application, it