The device "netFIELD Compact X8MC Next" supports four 24-volt compatible digital inputs and four digital outputs.
The GPIO sysfs interface for userspace access to the 4DI/4DO (symbolically "ied_di4_o4") is configured in the device tree bindings to be exposed under "/var/platform/".
The following GPIOs are exposed under "/var/platform/" (use "ls /var/platform/" to just list the subfolders)
DIs:
ied-di4o4_i0
ied-di4o4_i1
ied-di4o4_i2
ied-di4o4_i3
DOs:
ied-di4o4_o0
ied-di4o4_o1
ied-di4o4_o2
ied-di4o4_o3
Read/Write access
Standard file access functions are used to access the sysfs interface.
Example in C using stdio functions
The fopen() function binds a named GPIO to an access stream.
Read access:
fp = fopen("/var/platform/ied-di4o4_i0", "rb")Write access:
fp = fopen("/var/platform/ied-di4o4_d0", "wb")The fread() function reads the current state of a DI signal
char buffer[32];
bytesread = fread(buffer, sizeof(char), sizeof(buffer)-1, fp);
fclose(fp);
if (!bytesread){
/*error*/
} else {
/* success evaluate bytesread[xxx]*/
}
The fwrite() function writes the state "1" to a DO signal
byteswrite = fwrite("1", sizeof("1"), fp);
fclose(fp);
if (!byteswrite){
/*error*/
} else {
/* success */
} Example as command line
Writing the state "1" = on to a DO signal
echo 1 > /var/platform/ied-di4o4_o2
Reading and outputting the current state of a DI signal
cat /var/platform/ied-di4o4_i1