Sunday, 12 February 2017

Build an info station using Adafruit Feather

Everyone needs an info station. Press a button to quickly get the information you want! This project uses a Feather Huzzah with Wifi, an arcade button and an OLED i2C display.

What does it do?

  • On startup, the info station connects to your WiFi.
  • It displays a message: 'please press button'.
  • When pressed, the API of your choice is called, the response is parsed and displayed.
  • After a given duration, the display goes back to showing the message: 'please press button'.

In my case, I have a bus stop outside my building. When I press the button, it fetches the real time data showing when the next buses are due. The info updates once a minute for 5 minutes, then goes back into sleep mode. The reason I don't show the data all the time is that the API can only be called a limited number of times every month.



Step 1 - Prettify the button

The arcade button I bought looks nice, but I felt it would look even nicer if it had a LED light inside. But since a LED would be hard to fit in there, I decided to go with a LED sequin instead. I usually use these for wearables, but the sequin is very easy to work with; one end connects to voltage and the other to ground. So just start with soldering two wires onto the sequin. Make sure you use different colors on the wiring so you later know which is plus and minus.

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To test the wiring, just connect your Feather to a computer using a micro USB cable and hold the ends of the sequin wires to the pins for 3V(+) and GND(-). The sequin should light up.

Use a small screwdriver to pry open the button by pressing the clips on both sides. Glue the LED sequin to the inside of the actuator so it will shine through the white plastic. Carefully put the button together again, pulling the wires out through the side slits without damaging the solder joints or wires. Test the sequin again using the Feather. A lovely shiny button! Who could possibly resist pressing it?



Step 2 - Solder pin headers into the Feather pads

In all Arduino and Raspberry Pi projects, one thing to remember is to always test the components before soldering. The easiest way to do that is by using a breadboard. If the pins are just pads, like on the Feather, I usually solder pin headers into them so I can plug everything into a breadboard and try out connections and code.

The Feather either comes with pre-soldered headers, or with a set of headers that you can solder yourself. There's no need to solder all of the pins. The ones used for this project are 3V, GND, GPIO2, GPIO4 and GPIO5. When you solder the headers, plug the long end of the pins in the header strip into the breadboard, place the Feather over the pins and solder the short end of the pin that's poking up through the pad. Now you can connect jumper wires and test out your connections to other components.


Step 3 - Test the Feather

To use the Feather Huzzah, we need to install the ESP8266 Board Package in the Arduino IDE. Under Preferences >> Additional Boards Manager Urls, add the url http://arduino.esp8266.com/stable/package_esp8266com_index.json. Next, use the Boards manager to install the ESP8266 package.


Restart the IDE and you should now be able to select the board Adafruit HUZZAH ESP2866 in the Boards manager.


Select the correct USB serial port under Ports and connect the Feather using a micro USB cable. Open a new sketch and insert the following code:
  void setup() {
    pinMode(0, OUTPUT);
  }

  void loop() {
    digitalWrite(0, HIGH);
    delay(500);
    digitalWrite(0, LOW);
    delay(500);
 }
The sketch will blink the built in red LED on GPIO0 every 500 ms. Save the sketch and press Upload to upload it to your Feather. If you have trouble connecting to the Feather it can be due to a faulty USB cable, it has to be able to transfer data, or issues with discovering the correct serial port. I have one USB cable that I know work well, and many that just won't connect my boards. If your LED blinks on your first attempt, congratulations! :)


Step 4 - Connect and test the button

To connect and try out the button, solder wires onto the gold plated connectors of the button. Use shrinking tube to cover the joints.

Peel and tin 5mm at the other end of the wires so you can push the wires into the breadboard. Connect one wire from the button to ground on the Feather and the other to GPIO2.

In the Arduino IDE, find the example Button under Examples >> 02.Digital. The example lights up a LED when a button is pressed. Most boards have a built in LED you can use. On the Feather, the built in red LED is on GPIO0. So change the sketch to use 0 for the LED pin, upload the sketch to the Feather and make sure your button works and the Feather can detect the state changes when you press the button.


Step 5 - Connect and test the display

The display I chose is an i2c OLED display with pre-soldered headers and 4 pins, very easy to work with. SPI displays are generally a bit faster but need more pins. Some microcontrollers are more suited for SPI, some displays need a bit of tampering to use i2c. But both work fine, it's just a matter of changing the wiring and number of pins.

Plug the display into the breadboard next to the Feather using the headers. Using male to male jumper wires, connect VCC to 3V, GND to GND, SCL to GPIO5 and SDA to GPIO4.

To communicate with the OLED display we need to install the library Adafruit SSD1306. Go to the Github repo and download a zip-file of the repo. Unpack it, rename it Adafruit_SSD1306 and place the folder in your Arduino/libraries/-folder. If this is the first library, you might have to create the folder libraries. Then do the same with the Adafruit GFX Library. This folder should be named Adafruit_GFX and placed in the same libraries-folder as SSD1306.

Restart the IDE and open File>>Examples. You should now have access to the Adafruit SSD1306-examples.


Pick the example corresponding to your display. In my case, the 128x64 i2c. Since my display does not have a RESET-connector, I change the pin for OLED_RESET to the default, which is -1. I also change the initiation of the display to the correct i2c-address, 0x3C. To find out the i2c-address, you can use the i2c-scanner from Arduino Playground.
  #define OLED_RESET -1
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);  
Now upload the sketch to your Feather. Hopefully you have a working connection between the two components, and a working display.


Step 6 - The code

Now when all things are working and connecting to each other, it's time to try it out with the actual code. My example can be found at github.com/asalilje/nextbus. In order to get that exact code to work, you need to register with trafiklab.se to get an API-key, and add your wifi SSID and password. You also need to add the Arduino Json-library to Arduino IDE. But I'm sure the buses at my stop are really irrelevant to you, so do whatever you want here. There are lots of fun API's to play around with. :)

I chose to do the JSON-parsing on my Feather. In retrospect, I should have built a Node API on a Raspberry Pi that called the external API and fetched the nicely parsed data from there instead.

Whatever you choose to do, make sure your application works as expected before you start to solder and encase the components.


Step 7 - Putting it all together

Think carefully before you start to put all the components together. It's a good idea to solder one component at the time and check after every step that it still works as expected. Nothing worse than soldering everything at the same time and then discover it's not working and be completely lost as to where it's gone wrong. Trust me, I've been there...

Since the button snaps into a hole from the top down, it needs to be mounted before the wires are attached to the Feather. I used a simple small cardboard with a top lid and mounted the button first. Then I soldered the button wires to GND and GPIO2, and the LED sequin wires to GND and 3V. Button done, yay!

I almost always keep the headers when I'm soldering components together, since I think it's easier to get right than soldering wires directly into the pads. I solder the wires onto the pins and then use shrinking tube to cover both joints and pins. Heating shrinking tube with a hair dryer works perfectly!


For the display, solder VCC to 3V, GND to GND, SCL to GPIO5 and SDA to GPIO4. As you notice, GND and 3V on the Feather are connected to multiple components. You might want to twin those wires together and tin them into one before soldering them onto the Feather pin.

That's basically it! Mount your info station on the wall where you need access to your quick info and enjoy the seconds you save by not having to get exactly the same information on your phone. :)

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