TouchShield Slide Two-way Communications

Over last summer, I got the GamePack from Liquidware which includes a touch screen display, joystick, microcontroller, and battery pack. With this kit you can make a GameBoy from scratch. With some blood, sweat, and tears, I was able to re-create some games like Asteroids and Tetris.

The touch screen is called the TouchShield Slide which is a 320×240 OLED and resistive touch screen. The screen also has a microcontroller that is Arduino compatible and expands your program space. Since the screen is really a microcontroller in disguise, it can be used for many types of projects. Overall I am very happy with the screen, but I realized I didn’t know how to use it very well. I set out to learn and develop a protocol / reusable library that allows the screen to talk to a microcontroller and vice-verse. So I wanted to take a moment and explain what I learned – maybe you can get going faster than I did.

The Goal

My goal is to be able to display data on the screen that has been received from another device. The data requested would be initiated by a touch on the screen. The protocol has to be consistent and reliable, while being flexible enough to be the basis for future projects.

Touch -> TouchShield Slide -> Arduino -> TouchShield Slide

Programming Tips and Tricks

I found quite a few libraries and resources on liquidware.com.  I also discovered quite a few important things through my trial and error. My biggest frustration was with programming and figuring out the IDE. Here are some tips.

  • To program the screen use the Antipasto Arduino / Aardvark IDE
  • Program the screen and Arduino separately – make sure the IDE has the proper device selected
  • To put the screen in program mode, press the switch beside the power connector – it’s in program mode when the LED on the backside is red

TouchShield Slide Serial

Serial data sent and received by the TouchShield Slide uses the hardware serial lines.

To setup the serial connection, place this line in your setup code block:

Serial.begin(9600);

Now you can read and write to and from the serial buffer. To read in a whole string, use a byte array to store bytes from the serial buffer when serial data is available. To write to the serial buffer, simply use serial print.

char charIn = 0;
byte i = 0;
char stringIn[32] = “”;

while(Serial.available()) {
charIn = Serial.read();
stringIn[i] = charIn;
i += 1;
}

Serial.print(“A”);

Arduino Serial

On the Arduino side, you have to use some form of Software Serial that sends and receives data on Pins 2/3. I have found that the Adafruit SoftSerial Library, “AFSoftSerial.h”, works the best. It seems to be reliable and produce consistent results when talking to the TouchShield Slide. Reading and writing from a software  serial buffer is about the same as a hardware one with this library.

To use software serial, follow these steps:

  • Include the “AFSoftSerial.h” library in your Arduino code header space
  • Define the RX and TX pins
  • Instantiate the software serial
  • Initiate the software serial line
#include AFSoftSerial.h

#define RX_PIN 3
#define TX_PIN 2

AFSoftSerial touchSerial = AFSoftSerial(RX_PIN, TX_PIN);

void setup() {
touchSerial.begin(9600);
}

Demo Project

I took a moment to put together all of the things that I learned into a quick demo project. This project displays a random number on the screen. The random number is being generated by an Arduino, sent via serial, and requested by a touch of the TouchShield Slide.

Random Number from Arduino Displayed after Detecting a Touch…

Visit Liquidware’s App Store to download the source code and library for this demo project.

Internet-enabled Message Center

What are you up to now?

I took the leap and bought an Arduino from LiquidWare. An arduino is an open-source microcontroller that has a processor, some digital I/O pins, and analog inputs. You can create little standalone programs that monitor inputs, control LEDs, and pretty much anything that you dream up. My favorite projects are ones that involve the Internet. A microcontroller is rather simple by itself, but what if it could use the web to get answers, send email, maybe update my Twitter status? That means there is a unlimited number of projects ahead – Microcontrollers collaboarating in cyberspace. The missing link for the web part is the ioBridge IO-204. I know you are no stranger to the the IO-204, but for those of you who have not heard. The IO-204 sits on my network and relays data from its channels to ioBridge.com servers and back into my network. It allows for remote control and monitoring without network configuration and programming. One of the expansion boards is a two-way serial board that accepts serial strings and connects them to APIs of web services that ioBridge interfaces to and sends back responses. For instance, I can send the commands, “[[[calc|9*9]]]” and this returns 81. OK, maybe not impressive on the surface, but that result came from Google Calculator. Anything Google Calculator can solve, your microcontroller has access to those results. For more examples, visit the Serial Web Services API on the wiki.

Message Center Project

I wanted to combine these two worlds with a sample project – maybe it will inspire you to come up with something better, spark some ideas that you have. I have my arduino measuring my outside temperature here in Pittsburgh, which is an analog input scaled to Fahrenheit. At any moment I can press a button and get the temperature on the LCD screen – no Internet required. Since I have been planning a work trip to Atlanta, I also wanted to compare my temperature with hot-lanta’s. So, my project solves that. Using the “weather command”, I am able to get the weather anywhere in the world by zip code or city name.

I added a few more things to the message center. With another button I can get the stock quote of Google. My strike price was $405, so I have been watching it close. If it gets below $405, I get an automatic email from my message center. The stock quote comes from the Yahoo Financials API.

I have one more button that emails me a secret message when it’s pressed. I put this in here for when my mom comes into my room from when I am on the road. It’s aptly label, do not press. Next time, I will hook it to a light sensor in the basement to catch her when she turns on my lights. I am sure you all have the same issues with your mom.


Source Code

The arduino requires some c-like programming and I wanted to include the sketch for you to steal and use for your projects. You will see how I send the serial commands from the arduino to the IO-204 using the UART serial connection (pins 0/1) and recieve and parse the incoming results. I use a SoftwareSerial port for the LCD results. The push buttons are software debounced and use pull-up resistors for solid digital connections. The LED’s linked to each button use a 330 ohm resistor to protect them. I was aided by the Arduino Inputs tutorial on Ladyada.net, Debounce Tutorial, and the iobridge Wiki / Forum. Please let me know if you have any questions, maybe I can help. I have learned a lot about handling strings on the arduino.

//
// Message Center using Arduino and the ioBridge IO-204
//
// An open-souce Shadowlord Project
// www.IamShadowlord.com


#include SoftwareSerial.h>

// SoftwareSerial Pins
#define rxPin 2
#define txPin 3

// Setup Software Serial
SoftwareSerial
softSerial = SoftwareSerial(rxPin, txPin);

// Global Setup
int middleLED = 11;
int rightLED = 10;
int leftLED = 12;

int leftButton = 5;
int
leftButtonCurrent = LOW;
int leftButtonReading;
int leftButtonPrevious = HIGH;
long leftButtonTime = 0;
long
leftButtonDebounce = 200;

int middleButton = 4;
int middleButtonCurrent = LOW;
int middleButtonReading;
int
middleButtonPrevious = HIGH;
long middleButtonTime = 0;
long
middleButtonDebounce = 200;

int rightButton = 6;
int
rightButtonCurrent = LOW;
int rightButtonReading;
int
rightButtonPrevious = HIGH;
long
rightButtonTime = 0;
long
rightButtonDebounce = 200;

int tempPin = 5;
int tempAnalog = 0;
int
tempF = 0;

char* currentRequest = "";

// Start up program
void
setup() {

pinMode(rxPin, INPUT);
pinMode(txPin, OUTPUT);

pinMode(leftLED, OUTPUT);
pinMode
(middleLED, OUTPUT);
pinMode(rightLED, OUTPUT);

pinMode(leftButton, INPUT);
pinMode(middleButton, INPUT);
pinMode(rightButton, INPUT);

softSerial.begin(9600);
delay(100);

Serial.begin(9600);
delay
(100);

Serial.flush();
delay(100);

// Setup LCD
clearLCD();
setBacklightBrightness(9);
delay
(1000);

// Test LEDs
digitalWrite
(leftLED, HIGH);
digitalWrite(middleLED, HIGH);
digitalWrite(rightLED, HIGH);

delay(1500);

digitalWrite(leftLED, LOW);
digitalWrite
(middleLED, LOW);
digitalWrite
(rightLED, LOW);

}

// Start main program loop
void
loop(){

// Get Analog Input and scale as temperature for ioBridge temperature sensor on arduino
tempAnalog = analogRead(tempPin);
tempF = tempAnalog / 6.875;

// Monitor left button status and debounce
leftButtonReading = digitalRead(leftButton);

if (leftButtonReading == HIGH && leftButtonPrevious == LOW &&
millis
() - leftButtonTime > leftButtonDebounce) {
if (leftButtonCurrent == HIGH) leftButtonCurrent = LOW;
else
{digitalWrite(leftLED, HIGH);
clearLCD();
delay
(100);
softSerial.print("Outside: ");
delay
(100);
softSerial.print(tempF);
delay
(100);
moveCursor("02", "01");
delay(100);
softSerial.print("Atlanta: ");
leftButtonCurrent = LOW;
//Request temperature in Atlanta via ioBridge
Serial.print("[[[weather|Atlanta]]]");
digitalWrite
(leftLED, LOW);
}
leftButtonTime = millis();
}

leftButtonPrevious = leftButtonReading;

// Monitor middle button status and debounce
middleButtonReading = digitalRead(middleButton);

if (middleButtonReading == HIGH && middleButtonPrevious == LOW &&
millis() - middleButtonTime > middleButtonDebounce) {
if (middleButtonCurrent == HIGH) middleButtonCurrent = LOW;
else
{currentRequest = "Google";
digitalWrite
(middleLED, HIGH);
clearLCD();delay(100);
softSerial.print("GOOG: $");
delay
(100);
middleButtonCurrent = LOW;
//Request Google Stock Price via ioBridge

Serial
.print("[[[stock|GOOG]]]");
digitalWrite
(middleLED, LOW);
}
middleButtonTime = millis();
}

middleButtonPrevious = middleButtonReading;

// Monitor right button status and debounce
rightButtonReading = digitalRead(rightButton);

if (rightButtonReading == HIGH && rightButtonPrevious == LOW &&
millis() - rightButtonTime > rightButtonDebounce) {
if
(rightButtonCurrent == HIGH) rightButtonCurrent = LOW;
else
{
digitalWrite
(rightLED, HIGH);
clearLCD();
delay(100);
softSerial.print("Alert: ");
delay
(100);
rightButtonCurrent = LOW;
//Send email via ioBridge

Serial
.print("[[[email|hans@nothans.com|Alert|Mom, is pressing your buttons]]]");
digitalWrite(rightLED, LOW);
}
rightButtonTime = millis();
}

rightButtonPrevious = rightButtonReading;

// Display serial messages
if(Serial.available() > 0){

delay(100);

char charIn = 0;
byte i = 0;
char
stringIn[32] = "";

while(Serial.available()) {
charIn = Serial.read();
stringIn[i] = charIn;
i += 1;
}

if (currentRequest == "Google") {

softSerial.print(stringIn);
int stockPrice = atoi(stringIn);
delay(100);
moveCursor("02", "01");
delay(100);
stockPrice = stockPrice - 405;
softSerial.print("Change: $");
delay
(100);
softSerial.print(stockPrice);
currentRequest = "";

}
else
softSerial.print(stringIn);
}

// End program loop
}

//
// ioBridge Serial LCD Functions and Parameters (for SoftwareSerial)
//

void displayMessage(char* message){
softSerial.print(message);
}

void clearLCD(){
softSerial.print(0xFE, BYTE);
softSerial.print("Z");
}

void setBacklightBrightness(int level){
// level
// 0=Off -> 9=Brightest

softSerial.print(0xFE, BYTE);
softSerial.print("B");
softSerial.print(level);
}

void setBacklightTime(int level, byte seconds){
// level
// 0=Off -> 9=Brightest

// seconds
// 01 = 1 seconds => 06 = 60 seconds


softSerial.print(0xFE, BYTE);
softSerial.print("T");
softSerial.print(level);
softSerial.print(seconds, BYTE);
}

void moveCursorHome(){
softSerial.print(0xFE, BYTE);
softSerial.print("H");
}

void turnCursorOn(){
softSerial.print(0xFE, BYTE);
softSerial.print("J");
}

void turnCursorOff(){
softSerial.print(0xFE, BYTE);
softSerial.print("K");
}

void turnBlinkingCursorOn(){
softSerial.print(0xFE, BYTE);
softSerial.print("P");
}

void turnBlinkingCursorOff(){
softSerial.print(0xFE, BYTE);
softSerial.print("Q");
}

void scrollMessage(int row, int speed, char* message){
// row
// 1=First Line -> 2=Second Line


// speed
// 0=Slowest -> 9=Fastest


softSerial.print(0xFE, BYTE);
softSerial.print("S");
softSerial.print(row);
softSerial.print(speed);
softSerial.print(message);
softSerial.print(0xFE, BYTE);
}

void moveCursor(char* row, char* column){
// row
// 01=First Line -> 02=Second Line

// column
// 01=First Position -> 16=Last Position


softSerial.print(0xFE, BYTE);
softSerial.print("L");
softSerial.print(row);
softSerial.print(column);
}

void drawHorizontalGauge(int row, char* leftLabel, char* rightLabel, char* length){
// row
// 1=First Line -> 2=Second Line

// leftLabel and rightLabel
// 2 character labels

// length
// a=Empty -> k=Full (filled in from left to right)


softSerial.print(0xFE, BYTE);
softSerial.print("G");
softSerial.print(row);
softSerial.print(leftLabel);
softSerial.print(rightLabel);
softSerial.print(length);
}

void drawVerticalGauge(int height){
// height
// 0=Bottom -> 8=Top (filled in from bottom to top)

softSerial.print(0xFE, BYTE);
softSerial.print("V");
softSerial.print(height);

}

Bonus Project

It’s simple, but I hacked together a power supply for the Arduino, which gets power from USB or a coaxial input from a transformer. I wanted to only run one brick, wall wart, so I hacked a USB cable. There are 4 wires in the USB cable (from pinouts.ru):

1 VCC Red +5 VDC
2 D- White Data –
3 D+ Green Data +
4 GND Black Ground

The IO-204 has a regulated 5VDC and ground (up to 1A – 4A total draw depending on supply) on each channel, so using a terminal strip, I connected the VCC and GND to a cut in half USB cable.

It’s magic – look ma, only one power source.