MIMO2+, Multiple Input
– Multiple Output
Module Technical Appendix
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Calculating Threshold Values
For setting the triggering values, the lower four least-significant bits of the equivalent binary number are dropped so that the
triggering configuration value is an 8-bit value (0 to 255 unsigned counts). For example, to set a trigger at approximately 2
Volts, the conversion will read approx. 2150 decimal counts. This corresponds to 866 hex counts. The corresponding trigger
point would be 86 hex (8-bit) counts or 134 decimal (unsigned) because the lower 4 bits would be dropped. Since 134 is
greater than 127 (refer to rules below), subtract 256 to obtain -122, which is the actual configuration parameter value.
Calculation from an unsigned count value greater than 127 to a negative parameter value
Parameter Value = Unsigned Value – 256
Calculation from a negative parameter value to unsigned count value …
Unsigned Value = Parameter Value + 256
(If the value is between 0 and 127, no conversion is necessary)
Triggering Notes
It is recommended to test triggering points using the Multilevel Sensor Command class to verify that configured trigger points
correspond to the desired input voltage levels.
The default trigger configuration for the analog inputs, SIG1 and SIG2, is a threshold around 1.85V. That is, the inputs will trigger
when the input is untriggered and the level goes above approximately 1.85V and will reset when the level is triggered and the
level goes below approximately 1.60V.
The trigger ranges for SIG1 and SIG2 are very flexible and can be changed to meet many application requirements. The triggering
can be configured to trigger between two thresholds or outside of the two thresholds. Also, a hysteresis can be configured for
each endpoint of the range so that the input is not constantly triggering and untriggering due to small changes in input voltage.
These triggering ranges are configured for each endpoint using the Configuration Command Class, Parameters 3 through 7 (SIG1)
or Parameters 9 through 13 (SIG2). Refer to the Configuration Command Class Parameters section above for details about these
parameters.
The following diagrams show the triggering ranges based on which way the input voltage is changing. For example, if ‘Trigger
between Thresholds’ is enabled, then the input will trigger when the voltage rises across the T
LH
threshold. Similarly, the input
will ‘untrigger’ if already triggered and the voltage falls across the T
LL
threshold.
