diff -r 4950117e9c11 -r ec6e1bf8d53b shell/gpio.sh
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shell/gpio.sh	Sat Nov 05 17:38:05 2016 +0100
@@ -0,0 +1,108 @@
+#!/bin/bash
+
+# GPIO.sh
+# Copyright © 2016 František Kučera (frantovo.cz)
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# GPIO.sh is a set of functions for controlling GPIO pins of Raspberry Pi or similar computer
+
+_gpio_valid_port() {
+	case $1 in 0|1|4|7|8|9|10|11|14|15|17|18|21|22|23|24|25)
+		return 0;;
+	*)
+		return 1;;
+	esac
+}
+
+# export -f _gpio_valid_port
+# seq 0 30 | xargs -n1 bash -c 'printf "%4s" "$0: "; _gpio_valid_port $0 ; if [ $? -eq 0 ]; then echo "valid port number"; else echo; fi'
+
+
+_gpio_log_error() {
+	# TODO: $(date --rfc-3339=seconds) or ● ?
+	echo -e "\e[1;31m$1\e[0m"; > /dev/stderr;
+}
+
+_gpio_log_warning() {
+	echo -e "\e[2;33m$1 \e[0m"; > /dev/stderr;
+}
+
+
+# open (export) the port and set its direction
+# parameters:
+#	port number
+#	direction: in/out
+gpio_open() {
+	local port="$1";
+	local direction="$2";
+	if [ $# -ne 2 ] || [[ "$direction" != @("in"|"out") ]]; then _gpio_log_error "usage: ${FUNCNAME[0]} <port> <in|out>"; return 1; fi
+	if ! _gpio_valid_port "$port";                          then _gpio_log_error "invalid port number: $port";            return 1; fi;
+	
+	if [ -d  "/sys/class/gpio/gpio$port" ]; then 
+		_gpio_log_warning "port $port is already exported → will just set direction: $direction";
+	else
+		echo "$port" > "/sys/class/gpio/export" || return 1;
+	fi;
+	
+	echo "$direction" > "/sys/class/gpio/gpio$1/direction";
+}
+
+
+# close (unexport) the port and set its direction
+# parameters:
+#	port number
+gpio_close() {
+	local port="$1";
+	if [ $# -ne 1 ];               then _gpio_log_error "usage: ${FUNCNAME[0]} <port>"; return 1; fi
+	if ! _gpio_valid_port "$port"; then _gpio_log_error "invalid port number: $port";   return 1; fi;
+	
+	if [ -d  "/sys/class/gpio/gpio$port" ]; then 
+		echo "$port" > "/sys/class/gpio/unexport";
+	else
+		_gpio_log_error "port $port is not open";
+		return 1;
+	fi;
+}
+
+# reads value of given port
+# parameters:
+#	port number
+gpio_read() {
+	local port="$1";
+	if [ $# -ne 1 ];               then _gpio_log_error "usage: ${FUNCNAME[0]} <port>"; return 1; fi
+	if ! _gpio_valid_port "$port"; then _gpio_log_error "invalid port number: $port";   return 1; fi;
+	
+	if ! cat "/sys/class/gpio/gpio$port/value"; then
+		_gpio_log_error "unable to read value of port $port";
+		return 1;
+	fi
+}
+
+# writes the value to given port
+# parameters:
+#	port number
+#	value: 0/1
+gpio_write() {
+	local port="$1";
+	local value="$2";
+	if [ $# -ne 2 ] || [[ "$value" != @("0"|"1") ]]; then _gpio_log_error "usage: ${FUNCNAME[0]} <port> <0|1>"; return 1; fi
+	if ! _gpio_valid_port "$port";                          then _gpio_log_error "invalid port number: $port";  return 1; fi;
+	
+	if ! echo "$value" > "/sys/class/gpio/gpio$port/value"; then
+		_gpio_log_error "unable to write value $value to port $port";
+		return 1;
+	fi
+}
+