Table of Contents
Controlling the GPIO pins on Raspberry Pi board
The aim of this exercise is to prepare software written in the C# language under Windows 10 Core system for Raspberry Pi 3 board. The software application blinks LEDS connected to the appropriate Raspberry Pi GPIO pin ports in specific order. The hardware module contains 4 red LEDS which can be turned on/off using Windows 10 GPIO SDK functions.
Step 1
Hardware preparation. Mount the LEDs module into 40-pin Raspberry Pi connector.
Step 2
To control selected GPIO pins in C# language available for UWP platform create the UWP solution as it was described in the Hello World! application. In the MainPage.cs file add the source code:
/******************************************************************************************************************************** * * SAMPLE GPIO CONTROL PROGRAM * * Sample LED control program for students laboratory purposes. * Presents the Raspberry Pi 2/3 IoT ability to control * GPIO output pins blinking LEDs. * * * Raspberry Pi GPIO Layout - Model B+ * 1 - 3V3 Power 2 - 5V Power * 3 - GPIO2 SDA1 I2C 4 - 5V Power * 5 - GPIO3 SCL1 I2C 6 - GND * 7 - GPIO4 8 - GPIO14 UART0_TXD * 9 - GND 10 - GPIO15 UART0_RXD * 11 - GPIO17 12 - GPIO18 PCM_CLK * 13 - GPIO27 14 - GND * 15 - GPIO22 16 - GPIO23 * 17 - 3V3 Power 18 - GPIO24 * 19 - GPIO10 SPI0_MOSI 20 - GND * 21 - GPIO9 SPI0_SCLK 22 - GPIO25 * 23 - GPIO11 24 - GPIO8 SPI0_CE0_N * 25 - GND 26 - GPIO7 SPI0_CE1_N * 27 - ID_SD I2C ID EEPROM 28 - ID_SC I2C ID EEPROM * 29 - GPIO5 30 - GND * 31 - GPIO6 32 - GPIO12 * 33 - GPIO13 34 - GND * 35 - GPIO19 36 - GPIO16 * 37 - GPIO26 38 - GPIO20 * 39 - GND 40 - GPIO21 * ********************************************************************************************************************************/ using System; using Windows.Devices.Gpio; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.UI.Xaml.Media; namespace LEDTest { public sealed partial class MainPage : Page { // Raspberry Pi GPIO pins used for LEDs coontrol private const int LED_PIN1 = 4; // GPIO04 private const int LED_PIN2 = 23; // GPIO23 private const int LED_PIN3 = 24; // GPIO24 private const int LED_PIN4 = 12; // GPIO12 private GpioPin pin1; private GpioPin pin2; private GpioPin pin3; private GpioPin pin4; // Raspberry Pi GPIO Pin variables for blinking effect private GpioPinValue[] pinValue1 = new GpioPinValue[8]; private GpioPinValue[] pinValue2 = new GpioPinValue[8]; private GpioPinValue[] pinValue3 = new GpioPinValue[8]; private GpioPinValue[] pinValue4 = new GpioPinValue[8]; private DispatcherTimer timer; private SolidColorBrush redBrush = new SolidColorBrush(Windows.UI.Colors.Red); private SolidColorBrush grayBrush = new SolidColorBrush(Windows.UI.Colors.LightGray); private int Counter = 0; public MainPage() { InitLEDs(); // Initialize LEDs blinking procedure InitializeComponent(); // Initialize XAML Display view timer = new DispatcherTimer(); // define the timer timer.Interval = TimeSpan.FromMilliseconds(500); // set callback timer to execute each 500 ms timer.Tick += Timer_Tick; // register callback procedure InitGPIO(); // Initialze GPIO pins if ((pin1 != null) && (pin2 != null) && (pin3 != null) && (pin4 != null)) { timer.Start(); // start the timer } } // Initial LEDs state 8 stages void InitLEDs() { pinValue1[0] = GpioPinValue.High; // pins value state 0 pinValue2[0] = GpioPinValue.Low; pinValue3[0] = GpioPinValue.Low; pinValue4[0] = GpioPinValue.Low; pinValue1[1] = GpioPinValue.High; // pins value state 1 pinValue2[1] = GpioPinValue.High; pinValue3[1] = GpioPinValue.Low; pinValue4[1] = GpioPinValue.Low; pinValue1[2] = GpioPinValue.High; // pins value state 2 pinValue2[2] = GpioPinValue.High; pinValue3[2] = GpioPinValue.High; pinValue4[2] = GpioPinValue.Low; pinValue1[3] = GpioPinValue.High; // pins value state 3 pinValue2[3] = GpioPinValue.High; pinValue3[3] = GpioPinValue.High; pinValue4[3] = GpioPinValue.High; pinValue1[4] = GpioPinValue.Low; // pins value state 4 pinValue2[4] = GpioPinValue.High; pinValue3[4] = GpioPinValue.High; pinValue4[4] = GpioPinValue.High; pinValue1[5] = GpioPinValue.Low; // pins value state 5 pinValue2[5] = GpioPinValue.Low; pinValue3[5] = GpioPinValue.High; pinValue4[5] = GpioPinValue.High; pinValue1[6] = GpioPinValue.Low; // pins value state 6 pinValue2[6] = GpioPinValue.Low; pinValue3[6] = GpioPinValue.Low; pinValue4[6] = GpioPinValue.High; pinValue1[7] = GpioPinValue.Low; // pins value state 7 pinValue2[7] = GpioPinValue.Low; pinValue3[7] = GpioPinValue.Low; pinValue4[7] = GpioPinValue.Low; } // Initialize device GPIO. All LEDs control pins set to the output state private void InitGPIO() { var GPIO = GpioController.GetDefault(); // Show an error if there is no GPIO controller if (GPIO == null) { pin1 = null; pin2 = null; pin3 = null; pin4 = null; Time.Text = "There is no GPIO controller on this device."; return; } pin1 = GPIO.OpenPin(LED_PIN1); pin2 = GPIO.OpenPin(LED_PIN2); pin3 = GPIO.OpenPin(LED_PIN3); pin4 = GPIO.OpenPin(LED_PIN4); pin1.Write(pinValue1[0]); // set pin1 state LOW/HIGH pin1.SetDriveMode(GpioPinDriveMode.Output); pin2.Write(pinValue2[0]); // set pin2 state LOW/HIGH pin2.SetDriveMode(GpioPinDriveMode.Output); pin3.Write(pinValue3[0]); // set pin3 state LOW/HIGH pin3.SetDriveMode(GpioPinDriveMode.Output); pin4.Write(pinValue4[0]); // set pin4 state LOW/HIGH pin4.SetDriveMode(GpioPinDriveMode.Output); Time.Text = "GPIO pins initialized correctly."; } // XAML Timer callback function set to be executed each 500 ms private void Timer_Tick(object sender, object e) { LED1.Fill = pinValue1[Counter] == GpioPinValue.High ? redBrush : grayBrush; // Draw LED1 elipse Red/Gray = High/Low pin1.Write(pinValue1[Counter]); // Set pin1 value High/Low LED2.Fill = pinValue2[Counter] == GpioPinValue.High ? redBrush : grayBrush; // Draw LED2 elipse Red/Gray = High/Low pin2.Write(pinValue2[Counter]); // Set pin2 value High/Low LED3.Fill = pinValue3[Counter] == GpioPinValue.High ? redBrush : grayBrush; // Draw LED3 elipse Red/Gray = High/Low pin3.Write(pinValue3[Counter]); // Set pin3 value High/Low LED4.Fill = pinValue4[Counter] == GpioPinValue.High ? redBrush : grayBrush; // Draw LED4 elipse Red/Gray = High/Low pin4.Write(pinValue4[Counter]); // Set pin4 value High/Low Counter++; if (Counter > 7) Counter = 0; } } }
The code defines GPIO pins 4, 23, 24 and 12 as output. GPIO pins can be set as input/output. Because the board contains already resistors connected to the powers supply and LEDs (see the LEDs module schematic) the GPIO pins are set to turn off the internal pullup resistors. Line code 143: pin1.SetDriveMode(GpioPinDriveMode.Output);. The program simply loads the state of the LEDs from the Array[8] defined in the InitLEDs void. In the Main void the timer callback function Timer_Tick is registered to change LEDs state each 500ms. Callback function Timer_Tick each 500ms changes the state of the LEDs from GpioPinValue.High to GpioPinValue.Low (line 156). On the display, according to the LEDs state, the 4 circles change colour from red to brush synchronously.
Step 3
In the MainPage.xaml the code looks like:
<Page x:Class="LEDTest.MainPage" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="using:LEDTest" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d"> <Grid> <Grid.Background> <ImageBrush x:Name="Theme" ImageSource="Assets/AEI.jpg" Stretch="UniformToFill"/> </Grid.Background> <TextBlock x:Name="ZMiTAC" HorizontalAlignment="Center" Height="35" Margin="0,5,0,0" TextAlignment="Center" Text="ZMiTAC IoT Laboratory" FontSize="24" VerticalAlignment="Top" Width="360" Foreground="#FFD02BF5" RenderTransformOrigin="0.489,2.571" FontWeight="Bold"/> <TextBlock x:Name="Time" TextAlignment="Center" Margin="0,55,0,0" TextWrapping="Wrap" Text="500 msec" VerticalAlignment="Top" Foreground="#FF89F99D" FontWeight="Bold" FontSize="18.667" RenderTransformOrigin="0.5,1.8"/> <Ellipse x:Name="LED1" Fill="#FFF4F4F5" HorizontalAlignment="Center" Height="40" Margin="-150,145,0,0" Stroke="Black" VerticalAlignment="Top" Width="40"/> <Ellipse x:Name="LED2" Fill="#FFF4F4F5" HorizontalAlignment="Center" Height="40" Margin="-50,145,0,0" Stroke="Black" VerticalAlignment="Top" Width="40" RenderTransformOrigin="1.75,0.714"/> <Ellipse x:Name="LED3" Fill="#FFF4F4F5" HorizontalAlignment="Center" Height="40" Margin="50,145,0,0" Stroke="Black" VerticalAlignment="Top" Width="40"/> <Ellipse x:Name="LED4" Fill="#FFF4F4F5" HorizontalAlignment="Center" Height="40" Margin="150,145,0,0" Stroke="Black" VerticalAlignment="Top" Width="40"/> </Grid> </Page>
Step 4
Start debugging application and after deploy application package to the board SD card it will be displayed on the monitor.
