Help changing the state of a Digital Parameter Channel from inside a math function

Hello

You can not change the value of a digital, integer or floating parameter inside a math function.

If you need a channel which can have the values True and False, you should use the IDC channel

This is an internal digital, which value can change, dependant of certain events

Hope this helps

The solution I always use when I need to store a value and also have it adjustable as a parameter is the MEM channel. 

An example of this is the "automatic reset" solutions, by using a DP as input to the MEM, you get the correct value type (boolean), and you can use the logic of the MEM to do a reset. 

As the post says "expression not used", that to me sounds as if you are trying to write a Qcode expression in a separate channel that assigns a value to the Digital Parameter channel. That is not possible, a cornerstone in the IQAN system is that channel values are assigned in exactly one place, when that channel is calculated. 

You will get the hint "expression not used" when you have a line that is not doing anything. 

My guess is that you have written something like:

DP = False

If you have a channel named DP, this expression will evaluate to True when the value of the DP is false. It will not assign a value to the DP, that can only be done via the adjust item.