RCSwitch Linux Kernel module - operates 434MHz RCSwitches

18.07.2014 Stefan Wendler sw@kaltpost.de

Kernel module to operate RC power outlets (switches) through SYSFS. The module was devoped for a MIPS based Carambola board, but should run on any other Linux board as well.

The module exports a command interface to the sysfs which allows sending on/off commands to the RC swtiches. For example:

# turn switch off
echo "11111A0" > /sys/kernel/rcswitch/command

# turn switch on
echo "11111A1" > /sys/kernel/rcswitch/command

Credits:

Most of the parts for sending command to the RCSwitches over RF are taken from r10r [rcswitch-pi] (https://github.com/r10r/rcswitch-pi)

Project Directory Layout

The top-level directory structure of the project looks something like this:

• Makefile toplevel Make file
• Makefile.kmod include for building kernel modules
• README.md this README
• setenv_*.sh source to set cross-compile environment
• module the kernel module
• clients various client libs/programs to access the kernel module

Prerequisites

To compile this project the following is needed:

For OpenWrt:

• OpenWrt checked out and compiled for your target (see [this instructions] (http://wiki.openwrt.org/doc/howto/buildroot.exigence) )

Compilation

Note: you need perform a complete OpenWrt build first to succeed with the following steps!

Check setenv_*.sh

Edit setenv_*.sh, make sure OPENWRT_DIR points to the location of your OpenWrt base directory.

Set Cross-Compile Environment

To set the cross-compile environment use the following:

source setenv_*.sh

For the Carambola, this would be:

source setenv_carambola.sh

Compile

To compile the kernel module:

make

Installing on the target

Copy the rcswitch.ko found in module/src to your target (e.g. to /opt/rcswitch/module/.

Loading the module on the target

To load the kernel module at bootup, add the following to /etc/rc.local (before the exit 0 statement):

insmod /opt/rcswitch/module/rcswitch.ko

The module knows the following parameters:

tx_gpio		- Number of GPIO to which TX of 433Mhz sender is connected (default 9/CTS). (int)

en_gpio		- Number of GPIO to which 3v3 of 433Mhz sender is connected (default 7/RTS). (int)
		  Note: use -1 to disable use of enable GPIO. 

pulse_duration	- Duration of a single pulse in usec. (default 350) (int)

tx_repeat	- Number of how many times a message is repeated (default 10). (int)

E.g. if connected to CTS/RTS on the Carambola:

insmod /opt/rcswitch/module/rcswitch.ko tx_gpio=9 en_gpio=7

Or if TX is connected to pin 17 on RasPi, and Vcc to 5V:

insmod /opt/rcswitch/module/rcswitch.ko tx_gpio=17 en_gpio=-1

Usage

The module exports two entries to the sysfs (under /sys/kernel/rcswitch):

command		- Write Only. Accepts commands as defined below.  

power		- Read/Write. If the module was given a "en_gpio"i writing to `power` 
		  could be used to enable (1)/disable (0) the RF module. Reading from
		  `power` will return the current state (1=enabled, 0=disabled). 

The command format is defined as follows:

A command string has teh format: AAAAACS

Where:

AAAAA 	- address bits as set on the outlets DIP switches - e.g. '11111'
C	- channel A, B, C or D as set on the outlets DIP switches - e.g. 'A'
	  instead of A, B, C, D one could also use 1, 2, 3 or 4
S	- state 1 (on) or 0 (off) - e.g. '1'

Complete command string examples:

'11111A0'	- Switch channel A off for address '11111' 
'1111111' 	- Same as above 
'11111B1' 	- Switch channel B on  for address '11111' 
'1111121' 	- Same as above 

Commands are send to through the kernel modules sysfs entry at: /sys/kernel/rcswitch/command

Examples:

echo "11111A0" > /sys/kernel/rcswitch/command
echo "11111A1" > /sys/kernel/rcswitch/command