LTPS Movement Analysis

About the Application

This tutorial demonstrates the options LTPS can be integrated with AggreGate platform. Understanding of the process implies some basic knowledge of the platform. For communication with a device, we will use a TPS-driver mentioned in the previous tutorials. As for the platform, its models and alarms will be required. Let's create an App based on a function block diagram (FBD) and an ST function. We need the program to analyze the LTPS movement. As soon as the movements are detected the data of the ambient light sensor undergo a further analysis. If the light is not bright enough, the LED will be turned on for additional lighting.

What you need

Hardware

• 1 x Linux TPS3 (LTPS3) board, optionally in a TPB3 enclosure
• 1 x Tibbit #10 (power supply)
• 1 x Tibbit #18 (power jack)
• 4 x Tibbit #00_3 (2 direct I/O lines with 5V and ground)
• 1 x Tibbit #39_2 (large red LED)
• 1 x Tibbit #28 (ambient light sensor)
• 1 x Tibbit #36 (3-axis accelerometer)
• 1 x Tibbit #38 (pushbutton)

On-board Software

• AggreGate for Linux TPS (http://aggregate.tibbo.com/downloads.html)

Application

First, let's create a helper function for the data of the 3-axis accelerometer to be processed. A helper function will be written in ST language. It's time to create a code in ST with settings left default.

First

In the opened window, we create local variables.

Declaration of variables

VAR_INPUT
    newX, newY, newZ : DINT;
END_VAR   
VAR_OUTPUT
    averregeVal : DINT;
END_VAR   
   
VAR 
    differences : ARRAY[0..4] OF DINT;
    summ : DINT;
    i : LINT;
END_VAR

Now we can create functions for average (value) computing to reduce and eliminate random noise in the accelerometer output.

Implementation of the function

summ :=0;
FOR i := 4 TO 1 BY 1 DO
    differences[i] := differences[i-1];
    summ := summ + differences[i];
END_FOR;
differences[0] := newX + newY + newZ;
summ := summ + differences[0];
averregeVal := summ / 5;

Next

Implementation of the program logic. General program will be created by building a function block diagram (FBD). When creating a code, the following properties must be set:

1. Type - Program
2. Import - add a previously created calculateAverageMovement program
3. Task - true
4. Device Context - LTPS (already created)
5. Execution Type - Cycle.

Basic scheme of the program:

To implement the scheme, we will need a function block employing a previously created and imported function. As soon as the function block is added it requires function values to be set (see the screenshot below).

Then

To create a scheme, it is necessary to add several "inputs" with the expressions written in ST language. Inside themselves, the functions use the Aggregate expression language. Let's drill down two types of the expressions from the scheme:

А) Getting the value of one coordinate from the table.

OBJECT_TO_DINT(cell({users.admin.devices.TPSAgent:s6_tibbit36} , "accelerationX" , 0 , FALSE))
//1 - ST function "OBJECT_TO_DINT"
//2 - AggreGate expression language "cell" 
//cell paramiters:
//{users.admin.devices.TPSAgent:s6_tibbit36} - dataTable from context, "accelerationX" - field, 0 - row, FALSE - description. 

B) Getting the value from the table and after the comparison operation.

OBJECT_TO_DINT(cell({users.admin.devices.TPSAgent:s4_tibbit28}, "illumination" , 0 , FALSE)) < 30
//1 - ST function "OBJECT_TO_DINT"
//2 - AggreGate expression language "cell" 
//cell paramiters:
//{users.admin.devices.TPSAgent:s4_tibbit28} - dataTable from context, "illumination" - field, 0 - row, FALSE - description.
//3 - compare <.

Nested and simple environment

Conditions mentioned in the scheme are implemented as jumps to the label (see blocks 7 and 9). The jump condition will be successfully done right after the Boolean expression is calculated in the "input".

Next

It is necessary to create the model with a variable which controls alarms.

Result

Finally, it's time to run the program. As soon as it detects a motion it will change the variable value in the model and trigger the alarm in AggreGate platform. If the lighting is not sufficient the program will turn on the LED.