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<\/a>Controlling an external LED with serial command from PC<\/p><\/div>\n
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Theory<\/strong><\/p>\n The chipKIT Uno32 board features two hardware serial ports:\u00a0UART port1<\/strong>\u00a0and\u00a0UART port2.\u00a0<\/strong>Pin 0 and Pin 1 serves as RX<\/strong> and TX<\/strong> for\u00a0UART port1. <\/strong>These pins are\u00a0also used by the FT232R USB-to-Serial converter on the board. Similarly,\u00a0UART port2<\/strong>\u00a0uses Pin 39 and Pin 40 for RX<\/strong> and TX<\/strong> functions, respectively. We will use UART port1<\/strong> in this tutorial as it allows serial communication with the PC over an USB port.<\/p>\n The MPIDE has got a built-in serial monitor tool that allows you to watch any data that the Uno32 sends out its serial port. It also let you send characters from the PC back to the Uno32 board over the same serial interface. You can open the\u00a0serial monitor window by clicking on the serial monitor button in the toolbar. In a Windows version of MPIDE, the serial monitor window looks like this.<\/p>\n MPIDE serial monitor window<\/p><\/div>\n There\u00a0is a blank text box at the top where you enter text that you want to send to the chipKIT Uno32 board. Below that is a white space where the serial data sent by the Uno32 board will be displayed. On the bottom right side, you can select the Baud Rate (speed) of the serial communication. The default setting for Baud Rate is 9600 baud but you can select other baud rates from the drop-down menu. Note that the chipKIT board must be configured to the same baud rate for serial communication. You must free up the serial port before returning back to the programming mode of MPIDE. You can do that by closing the serial monitor window.<\/p>\n Circuit setup<\/strong><\/p>\n The experimental circuit setup for this tutorial is very simple. All you need is an LED and a 220? series resistor. The LED will be controlled from a serial command received from the PC. The picture below shows the LED connections to the Uno32 board. The LED is connected to Pin 2. Note that during serial communication, digital pins 0 (RX) and 1 (TX) are occupied and cannot be used for other I\/O purposes.\u00a0The board is connected to an USB port and receives power from there.<\/p>\n An external LED controlled through serial commands from a PC<\/p><\/div>\n Writing sketch<\/strong><\/p>\n In your setup function, you need to tell the Uno32 to open serial port. This is done by Serial.begin()<\/strong> command. The number within the parenthesis sets the baud rate of the serial communication.\u00a0The typical baud rate for communicating with the computer is 9600 but other speeds are also supported. Next you need to define Pin 2 as output, which can be done using pinMode()<\/strong> function.<\/p>\n In order to send data from Uno32 to PC, MPIDE mainly offers two commands: Serial.print()<\/strong> and Serial.println()<\/strong>. Both of them send whatever is inside the parenthesis to the PC through the serial port. On PC’s side, the received data is displayed on the serial monitor window. However, the difference between using print<\/strong> and println<\/strong> is the way they print the data out the serial port. When you use Serial.print()<\/strong>, then the cursor remains at the end of whatever you just printed. So, if there is another print command following that then the new data will show up in the serial monitor window at the end of the previously received data, along the same line. On the other hand, Serial.println()<\/strong> prints data with a linefeed at the end that drops the cursor down to the next line after the data has been printed. Both of these commands can take many forms, which are described very well in the Arduino serial library page<\/a>.<\/p>\n Here’s the complete program to control the external LED with a command byte sent from the PC over the serial line. If the Uno32 receives ‘1’ from the PC, it turns the LED on. If it receives ‘0’, the LED is turned off. In response to the command, the Uno32 prints the new status of the LED back to the PC.<\/p>\n\n<\/a><\/a>\/*\n Tutorial 2: Serial interface between PC and chipKIT \n Description: chipKIT UNO32 receives commands from a PC through serial port\n and control an external LED connected to pin 2\n Board: chipKIT UNO32\n *\/<\/span>\n \nconst<\/span> int<\/span> LED_PIN =<\/span> 2<\/span>;<\/span> \/\/ LED is connected to digital I\/O pin 2<\/span>\nint<\/span> SERIAL_DATA;<\/span> \/\/ Variable to store incoming serial byte<\/span>\n \nvoid<\/span> setup(<\/span>)<\/span> {<\/span>\n Serial.begin<\/span>(<\/span>9600<\/span>)<\/span>;<\/span> \/\/ Sets the baud rate for serial transmission <\/span>\n pinMode(<\/span>LED_PIN,<\/span> OUTPUT)<\/span>;<\/span>\n\/\/ Send these messages to PC only once <\/span>\n Serial.println<\/span>(<\/span>"Serial interface between PC and chipKIT"<\/span>)<\/span>;<\/span>\n Serial.println<\/span>(<\/span>"1: LED ON, 0: LED OFF"<\/span>)<\/span>;<\/span>\n digitalWrite(<\/span>LED_PIN,<\/span> LOW)<\/span>;<\/span> \/\/ LED is off initially<\/span>\n}<\/span> \n \nvoid<\/span> loop(<\/span>)<\/span> {<\/span>\n \n if<\/span>(<\/span>Serial.available<\/span>(<\/span>)<\/span>><\/span>0<\/span>)<\/span>{<\/span> \/\/ Check if serial data is available.<\/span>\n SERIAL_DATA =<\/span> Serial.read<\/span>(<\/span>)<\/span>;<\/span> \/\/ If yes, read the incoming byte<\/span>\n if<\/span>(<\/span>SERIAL_DATA ==<\/span> '1'<\/span>)<\/span> {<\/span> \/\/ Check if the received byte is '1' <\/span>\n digitalWrite(<\/span>LED_PIN,<\/span> HIGH)<\/span>;<\/span> \/\/ If so, turn the LED ON<\/span>\n Serial.println<\/span>(<\/span>"LED is ON"<\/span>)<\/span>;<\/span> \/\/ and acknowledge.<\/span>\n }<\/span>\n if<\/span>(<\/span>SERIAL_DATA ==<\/span> '0'<\/span>)<\/span> {<\/span> \/\/ If the received byte is '0',<\/span>\n digitalWrite(<\/span>LED_PIN,<\/span> LOW)<\/span>;<\/span> \/\/ turn the LED OFF and<\/span>\n Serial.println<\/span>(<\/span>"LED is OFF"<\/span>)<\/span>;<\/span> \/\/ acknowledge.<\/span>\n }<\/span>\n }<\/span> \n}<\/span><\/pre><\/td><\/tr><\/table><\/div>\n\n