CSE 466 Lab 3: Switch Debouncing and Using Libraries with the LCD

Objectives

In this lab, you will install a push button, and you'll write a brief program to readit. You'll connect the color graphic Liquid Crystal Display and develop a sketch for it.

Suggested Reading and Resources

Helpful Hints

Suggested Steps

Part A- Switch Debouncing

  1. Check the momentary switch from your kit for the correct pinout, by using the voltmeter to check contuinity. Wire one pin of the switch to ground, and the other pin to Teensy pin 1.

  2. In Arduino, Load "File>>Examples>>02.Digital>>DigitalInputPullup". Read through the code and modify pin settings if needed to match your wiring. We'll use the on-board LED on Teensy. Compile and load the sketch and press your switch. The LED should light. Open the serial debug window. You should see the data changing when you press the button. If not, debug.(Note: the serial debug window may throw a jave memory exception and lock ip the Arduino IDE. Restart and substitute a delay(10) line for the Serial.println(sensorVal); line.

  3. Next connect an oscilloscope lead to Teensy pin 1, the switch pin. You should be able to see the voltage change as the switch is pushed.
    Look for noisy transitions like these:

    bounce switch
    Another example:
    input

  4. Now, in your sketch comment out Serial.println(sensorVal); Compile and run. Connect your scope probe to Teensy pin 13, the LED pin. Look for transitions there, like this:
    LED output

    Question 1: Do any false transitions get through to the LED? Why? If so, why don't you see the LED flicker?

  5. Uncomment Serial.println(sensorVal); and run.

    Question 2: Do the transitions on pin 13 change? Why?

In Arduino, Load "File>>Examples>>02.Digital>>Debounce". Again, read through the code and modify pin settings if needed to match your wiring. In addition, you will need to turn on the input pull-up. Compile and run, and verify correct operation.

Question 3: Are the transitions on pin 13 any different? If so, please describe.

Archive your sketches. You may want the code later.

Part B-the LCD and Graphics Library

  1. Find the Liquid Crystal Display in your kit. Note that the pin labels are on the backside.

    Connect the display to your Teensy as follows:
    display
    ILI9341 Pin Teensy 3.1Pin Notes
    VCC VIN Power: ~5 volts, from USB
    GND GND  
    CS 10  
    RESET +3.3V  
    D/C 9  
    SDI (MOSI) 11 (DOUT)  
    SCK 13 (SCK)  
    LED VIN Use 100 ohm resistor
    SDO (MISO) 12 (DIN)  

    https://www.pjrc.com/store/display_ili9341.html

    Check your work carefully. An error in wiring could damage the display! Double-check that you have NOT reversed the pins.

  2. In Arduino, Load "File>>Examples>>ILI9341_t3>>graphicstest". There are several ILI9341 libraries; be sure that you use the
    ILI9341_T3 library, which has been optimised for the Teensy 3.1. Compile, run, and open the serial debug window. This should demonstrate the display's capabilities.
    If nothing happens, unplug and check your wiring.
  3. Note the two lines at the beginning:

    #include "SPI.h"
    #include "ILI9341_t3.h"

    These refer to external libraries. Here is more information on #include and on Arduino libraries. Understand how these work, as we'll be using txternal libraries often.

  4. Now, using graphicstest as an example, write a sketch called OnOff that reads the switch and writes the word OFF or ON in large letters in the center of the display.

    Demonstrate your sketch to the TA.

  5. Download and run TFT_3DCube.ino. This sketch draws a cube in the center of the screen. Study the code, and then produce the following changes:

    Change the size of the cube with the potentiometer.

    Question 4: What are the limits to the size of the cube? How small can you still discern it to be a spinning cube? What is the largest size where it is still identifiable as a cube?

  6. Now, make a sketch called OnOffCube to use the button to start and stop the cubes rotation. Push for start, push for stop.
    Hint: use a state-variable that is toggled once for each button press.

  7. Next, make a sketch called HVCube to use the button to switch between horizontal and vertical rotation.
    Demonstrate your sketch to the TA.


Part C-Bluetooth Module and App control

Resources:

  1. Locate your Bluetooth BLE "Bluefruit" module. Solder pins on if needed (see lab 1 for soldering tips).
    bluetooth module

  2. This BLE module uses the SPI interface, the same as your LCD display module. The pins are wired as follows:
    BLE module     Teensy
    VIN                  Vin
    GND                 GND 
    RST                  6
    DFU                 not connected
    IRQ                  7
    CS                    8
    MOSI               11 common with other SPI devices (LCD)
    MISO               12 common with other SPI devices (LCD)
    SCK                 13 common with other SPI devices (LCD)

  3. Install the Adafruit nRF51 library shown above. Rename the uncompressed folder Adafruit_BluefruitLE_nRF51 and check that theAdafruit_BluefruitLE_nRF51 folder contains Adafruit_BLE.cpp and Adafruit_BLE.h (as well as a bunch of other files)

    Place the Adafruit_BluefruitLE_nRF51 library folder your arduinosketchfolder/libraries/ folder. 
    You may need to create the libraries subfolder if its your first library. Restart the IDE.

    We also have a great tutorial on Arduino library installation at:
    http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use

  4. Install the Android/iOS app shown above on a phone. Your Bluetooth module may require a firmware update, as discussed on this page.

  5. Load File>>Examples>>Adafruit BluefruitLE nRF51>>neopixel_picker, and compile and run it. Open the debug window. Make certain that the CS pin for the LCD is set as an output pin and is NOT SELECTED. Use your oscilloscope to be certain that only one CS pin is active. Refer to the datasheets if necessary.

  6. Run the Bluefruit LE app you installed, and connect to your board. Select "Controller" for mode. Then select "Color Picker". If all goes well you should be able to control the color of your neopixel display. Demonstrate this to a TA.

  7. Load File>>Examples>>Adafruit BluefruitLE nRF51>>controller, and compile and run it. Open the debug window.

  8. Run the Bluefruit LE app you installed, and connect to your board. Select "Controller" for mode. Then select "Control Pad".you should be able to see button changes in the debug window.

    There are several other examples to try if you wish, all of which demonstrate various features of the BLE module. Keep these uses in mind for your midterm project.

Deliverables