This driver adds a trigger that can be invoked by writing the sysfs file: trigger_now. This approach can be valuable during automated testing or in situations where other trigger methods are not applicable. For example no RTC or spare GPIOs. Last but not least, it allows user-space applications to produce triggers.

Configure kernel with make menuconfig (alternatively use make xconfig or make qconfig)

Linux Kernel Configuration
	Device Drivers  --->
		[*] Staging drivers  --->
			<*>     Industrial I/O support  --->
			    --- Industrial I/O support
			    -*-   Enable ring buffer support within IIO
			    -*-     Industrial I/O lock free software ring
			    -*-   Enable triggered sampling support
		    [--snip--]
		    
		          *** Triggers - standalone ***
		    < >   Periodic RTC triggers
		    < >   GPIO trigger
		    <*>   SYSFS trigger
		    < >   Blackfin TIMER trigger

When sysfs trigger support is enabled in the kernel configuration, there will be a /sys/bus/iio/devices/iio_sysfs_trigger/ folder which can be used for sysfs trigger management. The folder contains two files add_trigger and remove_trigger. New sysfs triggers can be created by writing an ID to the add_trigger file. E.g.

$ echo 0 > add_trigger  

This will create a new sysfs trigger, which you can access at /sys/bus/iio/devices/iio:triggerX, where X is the trigger number. Typically it will be 0 for the first trigger, 1 for the second, etc. The name of the trigger will be sysfstrigID where ID is the value written to the add_trigger file.

To remove a sysfs trigger, write the same ID used when registering it to the remove_trigger file. E.g

$ echo 0 > remove_trigger  

$ cd sys/bus/iio/devices/  
$ ls  
iio:device0   iio:device1   iio:trigger0  
$ cd iio:trigger0  
$ ls  
name   subsystem   trigger_now   uevent  
$ cat name  
sysfstrig0  
$ echo 1 > trigger_now  
$ echo 1 > trigger_now

IIO Documentation

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