Tasmota

Table of Contents

Supported Commands
Syntax

Beginning with Tasmota version 6.4.1.14, an optional feature for using mathematical expressions in rules was introduced. This feature is disabled by default but can be enabled by compiling from source and adding #define USE_EXPRESSION to user_config_override.h. Of course, #define USE_RULES is also required (enabled by default).

Supported Commands

Once the feature is enabled, the use of expressions is supported in the following commands:

Var
Mem
RuleTimer
If conditional statement (requires #define SUPPORT_IF_STATEMENT)

Syntax

Expressions can use of the following operators. They are listed by the order of operations priority, from higher to lower.

( ) (parentheses are used to explicitly control the order of operations)
^ (power)
% (modulo, division by zero returns modulo "0")
* and / (multiplication and division; division by zero returns "0")
+ and - (addition and subtraction)

Order of Operations Example

1+2*2 results in 5.0 as the multiplication is done first due to its higher priority
(1+2)*2 results in 6.0

In addition to numeric constants, the following symbolic values can be used:

Symbol	Description
VAR<x>	variable (<x> = `1..MAX_RULE_VARS`, e.g., `VAR2`)
MEM<x>	persistent variable (<x> = `1..MAX_RULE_MEMS`, e.g., `MEM3`)
TIME	minutes past midnight
UPTIME	uptime minutes
UTCTIME	UTC time, UNIX timestamp, seconds since 01/01/1970
LOCALTIME	local time, UNIX timestamp
SUNRISE	current sunrise time (minutes past midnight)
SUNSET	current sunset time (minutes past midnight)

Example: Mem1=((0.5*Var1)+10)*0.7

To use expressions in the Var, Mem and RuleTimer commands, an equal sign (=) character has to be used after the command. If not, the traditional syntax interpretation is used.

Statement	Var1 Result
`Var1=42`	42
`Var1 1+1`	"1+1" (the literal string)
`Var1=1+1`	2
`Var1=sunset-sunrise`	duration of daylight in minutes

Wiki has moved to link on the left.