Logic and diagnostics

These functions test values for Null and NaN, compare decimal numbers with a tolerance, pause a device script and report messages on a device. NaN is an unknown number, Null is a missing value — see Data types. The minimum Core version of each function is in Version requirements.

ISNULL#

ISNULL returns TRUE when a value is Null, a missing value — for example LastState on the first run of a Formula smart rule, or PARSEJSON with error ignoring when the path is not found.

1

ISNULL(value)

Returns — bool. Any type of value is accepted. NaN is a number, not a missing value, so ISNULL(NaN) is FALSE.

Example

IF(ISNULL(LastState), 0, LastState);
# Result: 0 on the first run of a Formula smart rule, then the previous result

See also — ISNAN, Scripts in smart rules.

ISNAN#

ISNAN returns TRUE when a number is NaN, an unknown value — for example the value of a device that is in error or has not been read yet.

1

ISNAN(number)

Returns — bool.

Remarks — NaN is never equal to anything. A comparison with the literal NaN, such as x = NaN, is rejected when you save the script. The argument must be a number: ISNAN(Null) stops the script with a run-time error, so test ISNULL first when a value can also be missing.

Example — write 0 when a device is in error or returns NaN

Use IF(ISNAN(x), 0, x) to pass on a number even while the source device is in error:

IF(ISNAN(x), 0, x);
# Result: 0 while the device is in error or returns NaN, otherwise x

When the value can be Null as well, check it first — OR does not evaluate its right side when the left side is already TRUE:

IF(ISNULL(value) OR ISNAN(value), 0, value);

Errors — Comparison with NaN is always false. Use the IsNaN method to check for NaN value. (when saving the script).

See also — ISNULL, EQUALS.

EQUALS#

EQUALS returns TRUE when two numbers differ by at most a tolerance (epsilon, 0.005 by default); use it instead of = for decimal values such as temperatures.

1
2

EQUALS(number1, number2)
EQUALS(number1, number2, epsilon)

Parameters

Returns — bool. Two NaN values count as equal, so EQUALS(NaN, NaN) is TRUE. A Null argument is a run-time error.

Example

EQUALS(21.499, 21.5);
# Result: TRUE
EQUALS(21.4, 21.5, 0.01);
# Result: FALSE
EQUALS(NaN, NaN);
# Result: TRUE

SLEEP#

SLEEP pauses a Modbus or Packet parser script for the given number of milliseconds (0 – 10 000) and returns that number.

1

SLEEP(milliseconds)

Remarks — While the script waits, the module does not poll its devices, so keep the pause short, typically a gap a device needs between two writes.

Example

MODBUSW(H, 100, Uint16, 1);
SLEEP(200);
MODBUSW(H, 101, Uint16, 1);

Errors

• SLEEP function not allowed in this context. — the script belongs to a smart rule (Equation, Formula or Script) or to a notification; it cannot be saved.
• Interval ‘X’ is out of range (0-10000) — at run time.

Available — Modbus and Packet parser scripts.

ADDERROR, ADDWARNING, ADDINFO#

ADDERROR, ADDWARNING and ADDINFO show an error, a warning or an information message on the device in the TapHome app and return TRUE.

1
2
3
4
5
6

ADDERROR(text)
ADDERROR(code, text)
ADDWARNING(text)
ADDWARNING(code, text)
ADDINFO(text)
ADDINFO(code, text)

Parameters

Remarks — The messages are evaluated on every run: a message disappears as soon as a run of the script no longer raises it.

Example

VAR alarm := MODBUSR(H, 599, Uint16);
IF(alarm > 0, ADDERROR("There are " + alarm + " active alarms"));
IF(GETBIT(MODBUSR(H, 600, Uint16), 0) = 1, ADDERROR(1, "Alarm 1 active"));
IF(GETBIT(MODBUSR(H, 600, Uint16), 1) = 1, ADDWARNING(2, "Filter change due"));

Errors — ADDERROR function not supported here. (or ADDWARNING, ADDINFO) in any script not listed under Available.

Available — read scripts of Modbus modules and devices; read, write and listener scripts of Packet parser. Not in Modbus write and initialize scripts, service attributes and service actions of either integration, smart rules or notifications.

See also — Modbus functions, Packet parser functions.

DEBOUNCE#

DEBOUNCE ignores the values of one device value read from the device for the given number of milliseconds and checks the value again when that time ends; writes to the device are not affected.

1

DEBOUNCE(deviceVariable, milliseconds)

Parameters

Returns — the interval. On a device value without a debounce filter the call does nothing.

Example

DEBOUNCE(St, 500);

Errors

• DEBOUNCE - Function is not available — the script is not a device script listed under Available.
• DEBOUNCE - invalid argument, must be a device variable

Available — Core 2026.1, build 36599 and later · Modbus device read and write scripts, Packet parser read, write and listener scripts.