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Waijung 2 User Guide

Navigation: ESP32 target > Block references > Other

Expression evaluator block

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How this block appears in a Simulink model?

exp_evl_1

What can be configured?

exp_evl_2

Configuration Parameter

Selectable Option/Value

Description

Number of parameters

 

Number of parameters expecting to compare

Parameter name size (bytes)

 

The size of the parameter name in bytes should be determined by the length of the longest name when comparing different names. For instance, when comparing "temp1" and "humidity1," the size should be 9 bytes because the parameter name "humidity1" is longer.

Filter expression size (bytes)

 

Filter expression size in bytes.For instance if the expression is "temp1>humidity1" the size should be 15 or larger value

Sample time (sec)

-1(inherited) or specify

Specify the sample time

 

INPUT Port

Port Name

Port Type

Date Type

Description

Parameter name list

Vector

uint8

Feed char vector with the parameter name list.For instance 'senor1,senor2'

Filter expression

Vector

uint8

Feed char vector with the filter expression.'sensor1 > 20 | sensor2 < 100'

Parameter values

Vector

uint8

Feed char vector with parameter current values.

OUTPUT Port

Port Name

Port Type

Date Type

Description

Status

Scalar

Boolean

The port provides an output that reflects the status of the filter expression. If the expression's condition is met, it outputs 1; otherwise, it outputs 0.

When to use this block?

This block is utilized for expression evaluation. When you need to obtain a status output by assessing an expression, you can employ this block. For a more comprehensive understanding, please refer to the example demonstrations provided.

How does this block work?

When formatting the filter expression, please adhere to the specified format. Keep in mind that the operators used do not conform to C standards, so refer to the provided example expressions when defining your filter expression.

Standard C operator

Modified operator

Example expression

Equal to (==)

=

X = Y

Not equal to (!=)

!

X ! Y

Greater than (>)

>

X > Y

Less than (<)

<

X < Y

Greater than or equal to (>=)

#

X # Y

Less than or equal to (<=)

@

X @ Y

Logical AND (&&)

&

X & Y

Logical OR (||)

|

X | Y

Example for Standard C expression

Example for Modified expression

(X > 50) || (Y > 20)

(X > 50) | (Y > 20)

(X >= 50) && (Y <= 20)

(X # 50) & (Y @ 20)

(X != 50) && (Y == 20)

(X ! 50) & (Y = 20)

Demo

How expression evaluator block works

Demo1 file: expression_evaluator_demo1.slx

Demo 1 : How expression evaluator block works

Description

This example serves as an educational tool to demonstrate how the expression evaluator block functions. Its main objective is to facilitate a clear understanding of the process required to correctly input parameter data in order to achieve the desired result.

 

Full Model

exp_evl_3

 

What should be happening?

Build the "demo1" file by compiling the provided demo file. Upon successful deployment of this file to the hardware, proceed to initiate the serial communication software for testing the aforementioned demo. In the software interface, choose the appropriate COM port to establish a connection for data monitoring.

 

exp_evl_4

 

After opening the serial monitor, you will notice that the status is initially set to 0 because the default parameter values do not meet the expression's condition. To test the true condition, please adjust the parameter values as follows to fulfill the expression's criteria.

 

exp_evl_5

 

To satisfy above expression, change the parameter values as below.

 

exp_evl_6

 

After that, rebuild the demo and open the serial monitor.

 

exp_evl_7

 

As illustrated above, the status has changed to 1 because the current parameter values now satisfy the filter expression condition. You can similarly test any expression of your choice and obtain the desired output.

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