Practical Arduino Cool Projects for Open Source Hardware- P16 pptx

CHAPTER 8  TOUCH CONTROL PANEL coordinates to control a 3D cube visualization. Processing is the sister project to Arduino: while Arduino is all about controlling physical events, Processing is all about visualization, image processing, and representing events graphically. In fact the Arduino IDE is based on the Processing IDE, so if you’re familiar with one, you’ll feel right at home with the other. To run the 3D cube program you’ll need to download the latest version of Processing from www.processing.org and install it on your computer. You can then download the sketch called TouchCube from the project page on the Practical Arduino web site. Processing programs follow a very similar structure to Arduino programs. They have a setup() function at the start that is called first, just as in Arduino, but rather than having a main program loop called loop(), it’s called draw() in Processing. The first thing the TouchCube program does is include the serial port class and create an instance called myPort. import processing.serial.*; Serial myPort; Then we set up variables for storing values from the Arduino and the current camera position. int touchX; // The X coordinate value received from the serial port int touchY; // The Y coordinate value received from the serial port float xPos = 512; // Current camera X-axis position float yPos = 512; // Current camera Y-axis position The setup function determines how big the window should be for the visualization using the size() function, sets the background fill color, and then opens the serial port to wait for values sent by the Arduino. One critical part of this setup function is the line right at the end that tells the serial port object to buffer (store) all values it receives until it gets a newline. We’ll get back to that in just a moment. void setup() { size( 800, 600, P3D ); fill( 204, 104, 0 ); myPort = new Serial(this, Serial.list()[0], 38400); myPort.bufferUntil('\n'); } The main program loop, called draw(), doesn’t need to do anything in this case because everything is done in an event handler. We still need to declare it though. void draw() { // Nothing to do here! } This next section might seem a little bit like magic because we declare a function that isn’t called from anywhere else in the code. However, the serial object uses this function as an event handler that is automatically invoked when a certain thing happens. In this case, it’s called when the serial port has buffered some input and then received a newline character as specified in the setup() function using bufferUntil('\n'). When that occurs, the serialEvent() function is called and the serial port object (called myPort) is passed into it so the event handler can process it. 129 CHAPTER 8  TOUCH CONTROL PANEL Very cool, because it means the program can totally ignore the serial port until there is a value waiting to be processed. The first thing the event handler does is pull the characters currently in the serial buffer into a variable called inString. void serialEvent( Serial myPort ) { String inString = myPort.readStringUntil( '\n' ); Then, if we’re happy that we were given a value and not just a lonesome newline character with no other characters, we continue processing it. We also have to chop off any whitespace so we have just the alphanumeric characters using the trim() function, as follows: if( inString != null ) { inString = trim( inString ); At this point we have a value that probably looks something like “32,874” stored in the variable, so we need to split it apart on the comma delimiter and put the two resulting chunks into an array. int[] coordinates = int( split( inString, ',' ) ); Finally, we have the X and Y coordinates separated out so we can do something with them. Because a touch screen that is not being touched will return a very high or very low value on the 0– 1023 range, we chop off the ends of the range. That way we only update the value if the screen is being touched, and leave it at its previous value if not. touchX = coordinates[0]; if( touchX > 20 && touchX < 1000 ) { When updating the coordinate, we apply some trickery to scale it out based on the size of the window we created earlier. The map function takes an input variable and then two ranges: the first is the acceptable range for the input, and the second is the required range for the output. What we’re doing here is taking the touchX value and saying that it currently falls onto a scale between 0 and 1023, but what we want to do is adjust it onto a scale between 0 and the width of the screen. What that means is that if the touchX value is halfway along the 0–1023 scale (at, say, 511), the result will be a value halfway along the 0–width scale. If width is 900, the result will, therefore, be 450. xPos = map( touchX, 0, 1023, 0, width ); } Then we do the exact same thing for the Y coordinate. touchY = int( coordinates[1] ); if( touchY > 20 && touchY < 900 ) { yPos = map( touchY, 0, 1023, 0, height ); } We’re almost ready to draw the cube! The next section activates lighting on the window and sets the background. 130 CHAPTER 8  TOUCH CONTROL PANEL lights(); background( 51 ); Finally, we set the camera position based on the coordinates we extracted and then draw the actual 3D cube. camera( xPos, yPos, 100.0, // eyeX, eyeY, eyeZ 0.0, 0.0, 0.0, // centerX, centerY, centerZ 0.0, 1.0, 0.0 ); // upX, upY, upZ noStroke(); box( 150 ); stroke( 255 ); line( -100, 0, 0, 100, 0, 0 ); line( 0, -100, 0, 0, 100, 0 ); line( 0, 0, -100, 0, 0, 100 ); } } With your Arduino connected and running either the TouchscreenCoordinates or the ReadTouchscreen sketches previously described to feed values through the serial port, and the TouchCube program running on your computer to read them, you should be able to move your finger around the Nintendo touch screen and see the view of the 3D cube change. One little catch though: make sure you turn off the serial monitor in your Arduino IDE first. Otherwise, Processing might not be able to open the port to receive the coordinates. You might find the display jumps around a bit because it updates immediately every time it receives a new coordinate. One approach to minimize this effect would be to use a small «FIFO» (First In, First Out) buffer that holds perhaps the last three sets of coordinates and then average the values to set the camera position. Construct Hardware for Home Automation Control Panel This project is quite straightforward in terms of both the software and the electronics. The tricky part is entirely in the physical construction of the panel itself so that you end up with a professional end result. Of course, the exact process will vary depending on what you will use as a mounting location so we can’t give precise steps that will work for you, but the following principles should apply in most cases and will help give you some inspiration for your own designs. For our prototype we wanted to fit the touch panel into a standard blank electrical wall plate with a printed background. The Nintendo DS touch screen just barely fits within the plate dimensions, so we sat the touch screen on top, marked around the edges with a fine felt-tip pen, then carefully cut out the center with a hacksaw to provide a neat clearance area just barely larger than the touch screen (see Figure 8-6). 131 CHAPTER 8  TOUCH CONTROL PANEL Figure 8-6. Wall plate with hole cut for touch screen The offcut piece was then trimmed to fit snugly into the resulting hole and a slot was cut to allow the touch screen connection tab to pass through. The pieces were then assembled upside down by placing the touch screen facedown on a smooth surface, sitting the plastic insert on top of it, fitting the modified faceplate over the whole lot, and pushing it down flush with the front of the touch screen. This caused the plastic insert to be recessed several millimeters into the faceplate, just perfectly aligned to hold the touch screen in place. Two-part epoxy glue was then run in a bead along two of the edges to attach the insert to the faceplate, and it was left to sit undisturbed while the glue cured. The result is a faceplate with the front panel recessed just enough for the touch screen to be set in front of it, plus a slot for the connection tab to pass through to the rear of the panel (see Figure 8-7). Figure 8-7. Wall plate with removed piece glued back in place behind its original location 132 CHAPTER 8  TOUCH CONTROL PANEL Next you need to decide what “buttons” you will display behind the touch screen, if any. For a really sleek look you can leave the touch screen totally blank and just use it as a large “touch on, touch off” button. You can even combine this with gesture recognition, such as sliding your finger up/down to increase/decrease volume or brightness of something you’re controlling. If you have electrically operated drapes you could use slide detection to control them: slide up to open the drapes, slide down to close them. With a bit of work you can even implement detection of things such as a circular motion similar to the scroll wheel on an iPod: clockwise to increase volume or brightness, counterclockwise to decrease. We created a simple graphic to go behind the touch screen to show the location of “hot zones,” which act as virtual buttons. This is placed on the wall plate and the touch screen is then laid on top. The graphic can be printed on a self-adhesive sheet and stuck in place to prevent it moving if you prefer. The areas designated on our prototype were on/off for an exhaust fan, open/closed for electrically operated drapes, and a slide bar for controlling lighting intensity (see Figure 8-8). Figure 8-8. Touch control panel with button graphics mounted behind the touch surface The background isn’t limited to just static elements, either. You could drill holes through the back panel and mount LEDs to display the current status of the item being controlled, or cut a rectangular hole and mount 7-segment LED or even LCD modules inside the panel. If you don’t expect to ever change the graphic overlay you could glue the touch screen in place with epoxy resin or similar, using a toothpick to apply a tiny amount along the edges where it won’t be seen. An alternative is to use a piece of self-adhesive vinyl. Cut a rectangle out of the center, slightly smaller than the touch screen, and stick it over the top so that it overlaps the panel. Then trim it around the edges so it forms a neat border. 133 CHAPTER 8  TOUCH CONTROL PANEL Calibrate Hot Zones Connect your newly constructed touch control panel to your Arduino, plug in the USB connection to your computer, and run the example code previously described. Open the serial monitor so you can see the X and Y values being reported by the Arduino. Draw a sketch of the layout of your buttons for reference, then use a stylus to touch the diagonally opposite corners of each button in turn. Write down the X,Y values on your sketch. For our prototype we printed an enlarged (150 percent) version of the background graphic and wrote the coordinates directly on it (see Figure 8-9). Figure 8-9. Calibrating touch control panel by noting X and Y coordinates for button regions What you’ll end up with is a set of coordinates that define the bounds of each button. If you’re using simple rectangular areas it’s pretty easy to then plot them into a table that shows the range of X and Y values for each button (see Table 8-1). 134 CHAPTER 8  TOUCH CONTROL PANEL Table 8-1. Example X and Y coordinates for button regions Button Xmin Xmax Ymin Ymax Fan on 696 866 546 831 Fan off 696 866 208 476 Drapes open 420 577 540 866 Drapes close 420 577 208 476 You’ll notice that on our prototype the X and Y values don’t start from either the bottom left or top left corner as you might expect: they start from the bottom right corner. This really doesn’t matter and is easy to compensate for in software, and can also be adjusted by changing the connections to the touch screen pins if necessary. In this case we could have changed the orientation by physically rotating the whole wall plate by 180 degrees to put 0,0 at the top left. Regardless, it works perfectly well in any orientation. Having defined the button corner coordinates it should be fairly obvious what needs to be done in software for the button hot zones: check the X and Y values and compare them to each defined range, and if a match is found that button is considered to have been pressed. The slide control isn’t much harder, and simply adds a response value proportional to the Y-axis position within the button. The ReadTouchscreen example sketch included with the TouchScreen library is a good starting point for a system to read button presses. All we have to do is extend the program by plugging the values from the coordinate table into a series of comparisons to determine which button is being pressed. #include <TouchScreen.h> TouchScreen ts(3, 1, 0, 2); void setup() { Serial.begin(38400); } void loop() { int coords[2]; ts.read(coords); Serial.print(coords[0]); Serial.print(","); Serial.print(coords[1]); if((coords[0] > 696) && (coords[0] < 866) && (coords[1] > 546) && (coords[1] < 831)) { Serial.print(" Fan ON"); } if((coords[0] > 696) && (coords[0] < 866) 135 CHAPTER 8  TOUCH CONTROL PANEL && (coords[1] > 208) && (coords[1] < 476)) { Serial.print(" Fan OFF"); } if((coords[0] > 420) && (coords[0] < 577) && (coords[1] > 540) && (coords[1] < 866)) { Serial.print(" Drapes OPEN"); } if((coords[0] > 420) && (coords[0] < 577) && (coords[1] > 208) && (coords[1] < 476)) { Serial.print(" Drapes CLOSE"); } if((coords[0] > 139) && (coords[0] < 327) && (coords[1] > 208) && (coords[1] < 866)) { Serial.print(" Illumination:"); Serial.print(map(coords[1], 208, 866, 0, 100)); Serial.print("%"); } Serial.println(); delay (1000); } As you can see the illumination slider reports not just that it is being pressed, but it also maps the Y coordinate from the range of the slide area onto a range of 0 to 100 to determine the percentage illumination to apply based on the position of the contact. Touching high on the slide scale will set the illumination high, and touching it low will set it low. There’s another improvement we can still make, which is to tweak the handling of the illumination slider to provide larger areas at the top and bottom of the range for full-on and full-off. With the current arrangement it would be very hard to turn the lights off entirely because if you touch near the bottom of the slider it will still probably be at 4 or 5 percent illumination, while undershooting the contact area will do nothing at all. There are two ways to fix this problem. The first, and probably the most obvious, is to divide the illumination slider into three separate zones so that it is treated as if it were three separate buttons. The top section could map to a “lights on” response, the bottom to a “lights off” response, and the middle remain as a variable illumination level. We can also do it in a slightly more subtle way by making use of an obscure property of the map() function to fudge the values at the top and bottom of the range. If you pass an input value to map() that is outside the origin range—either lower than the bottom of the range or higher than the top of the range—it returns a value that will exceed the destination range. We can, therefore, change the illumination slider section of the previous code by increasing the bottom value and decreasing the top value to shrink the range away from the ends of the hot zone, as follows: if((coords[0] > 139) && (coords[0] < 327) && (coords[1] > 208) && (coords[1] < 866)) { Serial.print(" Illumination:"); Serial.print(map(coords[1], 318, 756, 0, 100)); Serial.print("%"); } 136 CHAPTER 8  TOUCH CONTROL PANEL 137 It will then return negative values for contact right near the bottom of the range, and values greater than 100 percent for contact right near the top of the range. Negative values and readings greater than 100 percent obviously don’t make much sense, so next t he result needs to be constrained so it will be truncated to fit the desired range of 0 to 100. This is done with the constrain() function that we can wrap around the map() function, as follows: if((coords[0] > 139) && (coords[0] < 327) && (coords[1] > 208) && (coords[1] < 866)) { Serial.print(" Illumination:"); Serial.print(constrain(map(coords[1], 318, 756, 0, 100), 0, 100)); Serial.print("%"); } The complete version of this sketch, TouchControlPanel, i s available for download from the project page on the Practical Arduino web site. It’s then a matter of deciding what you want the various buttons to do. You could control devices directly using outputs on the Arduino, or you could attach an Ethernet or WiFi shield and have it send commands to a home automation system using web services Just for fun we’ve also created a matching program written in Processing called TouchContr olPanelDisplay, also available for download from the project page. If you run TouchControlPanel on your Arduino and TouchControlPanelDisplay on your computer you will see a visual representation on your computer of the current state of the hot zones on the touch screen. Mount Arduino Because wall plates have very little clearance and you only need four analog inputs to read the touch screen, this project works well with one of the small form-factor Arduino models such as the Pro Mini or the Arduino Nano. Make sure the breakout board connecting to the touch screen is securely mounted to prevent the connection ribbon from coming loose, and use short lengths of hookup wire to connect the pads to the analog inputs on the Arduino. The rest of the installation we'll have to leave to your ingenuity because you'll almost certainly have a different mounting location and requirements to us. . on the Practical Arduino web site. Processing programs follow a very similar structure to Arduino programs. They have a setup() function at the start that is called first, just as in Arduino, . big the window should be for the visualization using the size() function, sets the background fill color, and then opens the serial port to wait for values sent by the Arduino. One critical. prefer. The areas designated on our prototype were on/off for an exhaust fan, open/ closed for electrically operated drapes, and a slide bar for controlling lighting intensity (see Figure 8-8).