add an example to test PWM balanced mode

examples/pwmbalanced/pwm.go

@@ -0,0 +1,44 @@
+/*
+
+A PWM example by @youngkin, using the go-rpio library
+
+Fades a PWM hardware pin in and out using PWM mode balanced (vs. markspace)
+*/
+
+package main
+
+import (
+	"os"
+	"time"
+
+	"github.com/stianeikeland/go-rpio/v4"
+)
+
+func main() {
+	err := rpio.Open()
+	if err != nil {
+		os.Exit(1)
+	}
+	defer rpio.Close()
+
+	pin := rpio.Pin(19)
+	pin.Mode(rpio.Pwm)
+	pin.Freq(64000)
+	pin.DutyCycleWithPwmMode(0, 32, rpio.Balanced)
+	// the LED will be blinking at 2000Hz
+	// (source frequency divided by cycle length => 64000/32 = 2000)
+
+	// five times smoothly fade in and out
+	for i := 0; i < 5; i++ {
+		for i := uint32(0); i < 32; i++ { // increasing brightness
+			pin.DutyCycleWithPwmMode(i, 32, rpio.Balanced)
+			time.Sleep(time.Second / 32)
+		}
+		for i := uint32(32); i > 0; i-- { // decreasing brightness
+			pin.DutyCycleWithPwmMode(i, 32, rpio.Balanced)
+			time.Sleep(time.Second / 32)
+		}
+	}
+
+	pin.DutyCycleWithPwmMode(0, 32, rpio.Balanced)
+}

rpio.go

@@ -13,8 +13,8 @@ Also clock/pwm related oparations:
        - Set Duty cycle
 And SPI oparations:
        - SPI transmit/recieve/exchange bytes
-    - Chip select
        - Set speed
+       - Chip select
 
 Example of use:
 
@@ -60,8 +60,8 @@ on the output pins for the raspberry pi, and not the wiringPi convention.
 
 See the spec for full details of the BCM2835 controller:
 
-    https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
-    and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
+https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
+and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
 
 Changes to support the BCM2711, used on the Raspberry Pi 4, were cribbed from https://github.com/RPi-Distro/raspi-gpio/