onSetIsts and onSetIreg callback functions
techlobo opened this issue · comments
Can't decide if these have been left here for completeness, or if I am missing some use for these - but shouldn't these operations be disallowed?
Not declaring an mb.onSetIsts callback does not appear to interfere with operations - which it shouldn't, as the library should not be processing a 'Write Discrete Input' as modbus does not support that function code.
I note that one of the examples 'onGetShared.ino' provides a write callback function to 'write-protect ' the DI, but this scenario should not occur. If anything the library should raise an 'Illegal Function (01)' exception.
If there is a specific use for these could you please explain as I'm missing it (which may not be surprising)?
Actually having checked the example (onGetShared.ino) properly I note that it is actually using the Coil functionality. So if trying to use this to emulate DI operation then a dummy onSetCoil function would be reasonable - although I'm not sure why the Ists (or DI) functionality wasn't used directly.
Anyway that doesn't change the original question regarding the use of onSetIsts and onSetIreg.
For sure the library follows Modbus protocol specification and DI registers are readonly.
From other hand internally you can set value of DI by using mb.Ireg(ISTS_REG, value). That case onSetIsts callback make sense and fires.
So are these meant purely for use internally by the Slave and not associated with a Modbus function code?
In case of ISTS (onSetIsts) callback is called on internally initiated events only. In case of, for example, HREG (onSetHreg) callback called on updating Hreg by client requests also.