Working LED example

gpio/LED/README.md

@@ -0,0 +1,5 @@
+# LED GPIO
+
+- The long end of an LED is the Anode (+) and will need a 220ohm-ish resistor in line with the GPIO pin since it will power it via toggling a 3.3v voltage. 
+- Hook up the Cathode (-), the shorter end, to ground.
+- GPIO17 is the 11th pin on the raspberry pi header.

gpio/LED/main.go

@@ -11,7 +11,7 @@ import (
 func main() {
 	host.Init()
 
-	pin := gpioreg.ByName("GPIO11")
+	pin := gpioreg.ByName("GPIO17")
 	pin.Out(gpio.Low)
 
 	for {

gpio/README.md

@@ -2,6 +2,44 @@
 
 Ok, we are going to try the golang periph library with this.
 
+## Permissions
+
+The user running this binary must have `gpio` permissions on the Raspberry Pi.
+
+
+Check if you can read the device without being root
+
+```bash
+head -c 1 /dev/gpiomem > /dev/null && echo "Success" || echo "Access Denied"
+```
+
+If you get access denied then we can create a gpio user group with udev runs that grant permissions to the /dev/gpiomem device.
+
+```bash
+sudo groupadd gpio
+sudo usermod -aG gpio $USER
+```
+
+Create a udev rules file
+```bash
+sudo vim /etc/udev/rules.d/99-gpio.rules
+```
+
+Include the following:
+```txt
+# Access to the memory-mapped GPIO
+SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
+
+# Access to the gpiochip character devices (periph.io uses these)
+SUBSYSTEM=="gpio", KERNEL=="gpiochip*", GROUP="gpio", MODE="0660"
+```
+
+
+```bash
+sudo udevadm control --reload-rules && sudo udevadm trigger
+```
+
+
 ## Periph Library
 
 The Periph library is broken up into a number of sub libraries that are imported as needed. This allows the developers to decouple board implementations from drivers and devices.

gpio/udev/99-gpio.rules

@@ -0,0 +1,7 @@
+# Access to the memory-mapped GPIO
+SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
+
+# Access to the gpiochip character devices (periph.io uses these)
+SUBSYSTEM=="gpio", KERNEL=="gpiochip*", GROUP="gpio", MODE="0660"
+
+