Worklog #2: Handling joystick input on Arduino and LinkIt ONE.

After expanding the LinkIt ONE and Arduino analog inputs, I had to find a proper way to handle user input. The easier and most convenient way was using an analog joystick, so I ordered one off AliExpress.

As I figured it will take way too much time to get here, I decided I’d open up my Xbox 360 controller and use its joysticks in the meanwhile.

 

Butchered 360 controller. Red = VCC, Violet = GND, Yellow = A0, Orange = A1.

Butchered 360 controller. Red = VCC, Violet = GND, Yellow = A0, Orange = A1.

Joysticks are made by joining two analog pots together (one for vertical movement, and one for horizontal) and a tactile button.

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Worklog #1: Expanding LinkIt ONE/Arduino analog inputs.

While working on the controller for my RGB light system, I quickly noticed the analog inputs on the LinkIt ONE wouldn’t be enough. It only has three analog inputs while I needed at least 5 (2 for the controlling a joystick – which is basically two pots in one – and 3 for the color-choosing pots (R, G, B).

In order to increase the number of analog inputs, I decided to buy a 4052 4-channel (de)multiplexer. It costs roughly 50 cents and can handle both inputs and outputs: my local store had the ST version (HCF4052BE) so I bought that one, but TI also makes the same chip.

You can take a look at the datasheet here.

 

HCF4052B pinout.

HCF4052B pinout.

 

Operation is fairly simple: you connect your analog devices to pins 1, 2, 4, 5 (for channel Y) or 11, 12, 14, 15 (for channel X). The signal will then be output from pin 3 (for channel Y) or pin 13(for channel X), depending on the high/low states on pins 9 and 10 (B and A, respectively), which are connected to your Arduino/LinkIt.

Take a look at the following table to understand how the thing works:

 

HCF4052B truth table.

HCF4052B truth table.

This basically means that, provided that the INH pin (6) is connected to GND, if B and A are both low (connected to GND too), common pin 3 (or 13) will be connected to pin 1 – 0x (or pin 12 – 0y). If A is high (connected to VDD) and B is low, pin 3 (and 13) will then be connected to pin 5 (and 14), and so on.

Don’t forget to connect pin 16 to 5V and pin 6, 7 and 8 to GND.

Here is some example code to get this thing working for both Arduino and LinkIt, using only 3 of the 4 inputs. Try to modify the code to make it work for all pins!

In this particular case, I used this code to get the input from 3 potentiometers on the same analog pin.

 

And that’s it!

 

 

 

A new board came in today: SeeedStudio’s LinkIt ONE!

A few days ago, Seeed Studio posted a contest in which 10 pieces of their newest board, the LinkIt ONE, would have been given away to makers who had a good idea on how to use them for an hobby project.

You can find more info about the board here, it’s basically a 32-bit MCU development board which has lots of connectivity options built-in (GPS, cellular, Wi-Fi, Bluetooth, Audio, SD card) and is compatibile with the Arduino IDE. It is based on the MT2502A microcontroller.

I immediately applied for the contest and a few days later they replied saying they liked my idea and they were kind enough to send me a LinkIt ONE.

I received the board today (fast shipping with FedEx!) and it’s very neat.

This is how the whole package looks like. The board is definitely well-made and feels solid.

 

Center: LinkIt ONE board. Left: Wi-Fi/BT, GSM and GPS antennas. Right: 1000mAh battery (included) and 2 Grove modules I needed (not included)

Center: LinkIt ONE board. Left: Wi-Fi/BT, GSM and GPS antennas. Right: 1000mAh battery (included) and 2 Grove modules I needed (not included). SD and SIM slots on the back.

 

The info sheet is included in the package: By quickly looking at it, the only complaint I have is the limited number of PWM outputs (2, might be solved with software PWM libraries) and analog inputs (3, can be increased using a demultiplexer) compared to Arduino.

However, the price (79$) is unbeatable considering all its connection options: separate Arduino shields would definitely have a much higher cost. Moreover, the MCU is a lot beefier than your average Atmega. Keep in mind that this board runs at 3.3V.

More info and photos after the jump!

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