From e89c391f4db0d73212f530d04ceb237adf802c30 Mon Sep 17 00:00:00 2001
From: Wolfgang Werner <wwerner@picturesafe.de>
Date: Sun, 13 Dec 2020 08:31:18 +0100
Subject: [PATCH] add setup instructions

---
 README.md | 47 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 11 deletions(-)

diff --git a/README.md b/README.md
index d673e13..59d0581 100644
--- a/README.md
+++ b/README.md
@@ -1,27 +1,52 @@
-# pi-go-gpio
-Simple GPIO library for Raspberry Pi in Go
+
+# Simple GPIO library for Raspberry Pi in Go
 
 This module implements a Go module to manipulate the GPIO pins.
 
-Features
+## Features
+
 - only uses the sysfs mappings
 - with a proper setup it can be used without being root
 - tested on Raspberry Pi 3 / Raspberry Pi 4
 - tested with Ubuntu Server 20.10 (Groovy Gorilla)
 
-GPIO
+## GPIO
 
-This module uses the pin numbers to identify the GPIO ports.
+This module uses the pins to identify the GPIO ports.
 
-This image from [https://pinout.xyz](https://pinout.xyz) helps to find the right pins.
+This image from [https://pinout.xyz](https://pinout.xyz) proved helpful to find the right associations.
 
 ![Raspberry Pi GPIO Pinout](./doc/img/raspberry-pi-pinout.png)
 
 ## Setup
-/*
-We've whipped up a simple graphical .
-Feel free to print, embed, share or hotlink this image and don't forget to credit us!
-https://pinout.xyz
-*/
 
+I started with a fresh operating system image. 
+To enable user access to the gpio via sysfs one has to add these configurations.
+
+### add group to allow gpio access 
+
+Add a group to be used as owner of the gpio sys file entries
+
+´´´´shell
+~ addgroup gpio
+~ adduser ubuntu gpio
+´´´´
+
+### add configuration to udev rules
+
+Add a file ´´/etc/udev/rules.d/99-gpio.rules´´ with the following content, reboot your pi
 
+´´´´shell
+~ sudo su -
+~ cat /etc/udev/rules.d/99-gpio.rules
+#
+# gpio access for group gpio
+#
+SUBSYSTEM=="gpio", GROUP="gpio", MODE="0660"
+SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c '\
+chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio;\
+chown -R root:gpio /sys/devices/virtual/gpio && chmod -R 770 /sys/devices/virtual/gpio;\
+chown -R root:gpio /sys$devpath && chmod -R 770 /sys$devpath\
+'"
+~ reboot now
+´´´´