examples: add nrf example for all 4 built-in buttons and LEDs

Signed-off-by: Ron Evans <ron@hybridgroup.com>

src/examples/button2/button2.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"machine"
+	"time"
+)
+
+// This example assumes that you are using the pca10040 board
+
+func main() {
+	led1 := machine.GPIO{machine.LED1}
+	led1.Configure(machine.GPIOConfig{Mode: machine.GPIO_OUTPUT})
+
+	led2 := machine.GPIO{machine.LED2}
+	led2.Configure(machine.GPIOConfig{Mode: machine.GPIO_OUTPUT})
+
+	led3 := machine.GPIO{machine.LED3}
+	led3.Configure(machine.GPIOConfig{Mode: machine.GPIO_OUTPUT})
+
+	led4 := machine.GPIO{machine.LED4}
+	led4.Configure(machine.GPIOConfig{Mode: machine.GPIO_OUTPUT})
+
+	button1 := machine.GPIO{machine.BUTTON1}
+	button1.Configure(machine.GPIOConfig{Mode: machine.GPIO_INPUT_PULLUP})
+
+	button2 := machine.GPIO{machine.BUTTON2}
+	button2.Configure(machine.GPIOConfig{Mode: machine.GPIO_INPUT_PULLUP})
+
+	button3 := machine.GPIO{machine.BUTTON3}
+	button3.Configure(machine.GPIOConfig{Mode: machine.GPIO_INPUT_PULLUP})
+
+	button4 := machine.GPIO{machine.BUTTON4}
+	button4.Configure(machine.GPIOConfig{Mode: machine.GPIO_INPUT_PULLUP})
+
+	for {
+		led1.Set(button1.Get())
+		led2.Set(button2.Get())
+		led3.Set(button3.Get())
+		led4.Set(button4.Get())
+
+		time.Sleep(time.Millisecond * 10)
+	}
+}