Wearable technology is finding inroads into vertical markets such as healthcare, industrial, and automotive sectors. For example, special vehicle-health applications that monitor fuel efficiency, automobile speed, and the heart rate of a fatigue driver are being developed by Nissan, BMW, and Mercedes automotive manufacturers. The cost of wearable technology development boards ranges from low cost to highly expensive. Adafruit has created a cost-effective wearable platform called the Flora were special electronic modules have been designed to work with the microcontroller-based maker board. In this article, I’ll explore the Flora’s system architecture using block, circuit schematic diagrams, and its printed circuit board design. Also, to illustrate the ease in prototyping wearable device concepts, I’ll provide a mini how-to guide on wiring and testing a GPS (Global Positioning System) module with the Flora.
|The Flora is a cost-effective platform to build wearable devices and technologies. (Source: Adafruit Industries)|
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The Flora System Architecture
In exploring the Adafruit Flora I found the wearable device to be made of several subcircuits wired to an 8-bit microcontroller mounted on a small circular PCB (Printed Circuit Board). An Atmel ATMEGA32 microcontroller provides the processing power for the Flora, providing six digital pins, two communication pins, and two serial control lines. These digital pins and control lines are accessible to makers, designers, and engineers by half circle solder pads that surround the Flora’s perimeter. In addition, a reset switch, mini USB, dual regulated power supply (3.3V/5V supplies), and three LEDs (transmit, receive, and power) complete the Flora’s system architecture.
|The system architecture block diagram of the Adafruit Flora. (Source: Don Wilcher)|
Adafruit has provided all of the Eagle Cad circuit schematic diagrams and PCB layout drawings for engineers, designers, and makers interested in experimenting with the mechanical packaging and electronic designs of the Flora on their github website.
|PCB and circuit schematic diagrams for the Flora. Electronic designs were created using Eagle Cad software. (Source: Adafruit Industries)|
The Ultimate GPS Module
Before discussing the prototyping specifics of the Flora-GPS wearable device, here’s a few technical specifications about the module. The Ultimate GPS module uses the MT3339 chipset manufactured by GlobalTop Technology company. This GPS module is capable of tracking 22 satellites using 66 channels, according to the Adafruit website. All of the electronics are packaged in a 4 mm x 15 mm x 15 mm small plastic box. The module is soldered to a small circular printed circuit board with soldered pads.
|The Ultimate GPS module uses a tiny satellite receiver chipset. The solder pads makes it easy to prototype wearable devices. (Source: robotshop.com)|
The soldered pads provide accessible power, TX (transmit), RX (receive) pins for experimenting and prototyping wearable device concepts with the Flora. A small ceramic patch antenna for receiving satellite data sits on top of the box. The GPS module can operate on 3.3V drawing 20mA (milliamperes) of current tracking satellites and 25 mA during acquisitioning of data. The 20mA current draw makes it compatible with the Flora battery-operated wearable platform. It has a -165 dBm (decibel-milliwatt) sensitivity range with data acquisition updates occurring at 10Hz. A real-time clock can be created by adding a separate battery to the module. The design of the Ultimate GPS module’s PCB makes it compatible with Flora in building wearable devices. The circuit schematic diagram illustrates the ease in which the Ultimate GPS module can be wired to the Flora.
|The solder pads allow ease of wiring between the Flora and Ultimate GPS module. (Source: Don Wilcher)|
Prototyping a Flora-GPS Wearable Device
It’s quite easy to prototype a Flora-GPS device using ordinary alligator test leads. The circuit schematic diagram presented shows four basic electrical wiring connections. I’ve created an electrical wiring diagram using Fritzing software to show the clarity and ease in making these attachment points of the Flora to the Ultimate GPS module. Soldering solid wires to the solder pads and using a solderless breadboard is another alternative wiring method to use in building a Flora-GPS wearable device.
|The electrical wiring diagram shows the ease in which a GPS wearable device can be prototyped using the Flora. (Source: Don Wilcher)|
Here’s my prototype Flora-GPS wearable device wired together using alligator test leads.
|Alligator test leads allow quick wearable devices to be built with the Flora platform. (Source: Don Wilcher|
To assure the Flora is working properly, by serial communication with a USB cable, I uploaded the Blink LED code to the Flora. The Arduino IDE was used to upload the code to the Flora’s ATmega32 8-bit microcontroller’s RAM (Random Access Memory). The LED will blink at a total 2 sec Flash rate. With the code validating the proper USB communication with the Flora, the final step of the project build is to test the Ultimate GPS module.
|The Blink code used to test the Flora. Note the 1 sec on, 1 sec off Flash sequence to establish a 2 sec LED blink effect. (Source: Don Wilcher)|
Adafruit has provided a GPS library along with example code to get the module running effectively. I used the GPS HardwiredSerial Echo Test code to check both electrical wiring connections to the Flora and proper operation of the module.
|Adding the GPS_HardwareSerial_Echo_Test code to the Flora for testing the Ultimate GPS Module. (Source: Don Wilcher)|
The echo test software prints a series of GPS raw data on the Arduino’s Serial Monitor. The code simulates the data being received by a satellite if the GPS module is located outside. A key point to remember is to set the correct baud rate (9600) within the serial monitor correctly. If not, you’ll see scrambled data scrolling across the serial monitor’s window.
|The GPS Hardwired Serial Echo Test code displaying simulated satellite data on the Arduino IDE Serial Monitor. (Source: Don Wilcher)|
With code uploaded to the Flora, I was able to see the simulated data scrolling across the serial monitor’s window. Again, the test code was to test correct electrical wiring connections between the devices and proper GPS module operation. This example illustrates the ease in which makers, designers, and engineers can quickly prototype a low-cost wearable device using the Adafruit Flora platform. Additional information on pricing, software, and project ideas can be found on Adafruit’s website.
Don Wilcher is a passionate teacher of electronics technology and an electrical engineer with 26 years of industrial experience. He’s worked on industrial robotics systems, automotive electronic modules/systems, and embedded wireless controls for small consumer appliances. He’s also a book author, writing DIY project books on electronics and robotics technologies.