Internal Engine

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DUELink modules run an Internal Engine that is used to handle commands over multiple Interfaces, which include handling a stream of DaisyLink modules on the Downstream socket.

The engine is also used to extend the system capabilities and make it possible for the system to run Standalone.

The DUELink Engine has two modes Immediate Mode where commands are executed immediately, and Record Mode when commands are stored internally in the module.

note

DUELink Console handles both commands without the users needing to understand any details. This section help in understanding the engine internals.

Immediate Mode

Immediate Mode is ideal for sending single line command to trigger actuator into action or read sensor data for example. A command can be statled(200,200,50) to blink the status LED 50 times with a 200ms on/off interval. It is possible to send multiple commands in a single Immediate Mode shot by adding : between commands. For example: statled(200,200,50):Print("DUELink").

To test the interworking of the engine manually, instead of using Console, open a terminal software and connect it to the serial port presented by the connected DUELink module. We like Tera Term.

Hitting the escape key will result with > prompt. This is the Immediate Mode prompt. Entering > is also the command to switch to Immediate Mode. Keep a note of this once you switch to Recording Mde later.

note

Immediate Mode is the default mode when device is first connected.

Type Print("Hello World") and hit enter. The engine will execute the Print command and show Hello World.

tip

The engine handles backspaces and left/right arrows to help in editing the entered commands. It even has entered-command-history that can be fetched using up and down arrow keys.

Immediate Commands typically come from one of the Supported Systems over one of the Interfaces.

Record Mode

Record Mode takes the received commands and stores them internally. Those commands can be executed using run command. Use list to see a list of recorded commands, and new to erase everything and start new.

The Record mode is entered using the $ command. This will also switch the prompt to $. All statements entered are stored internally and not executed. The run command can be used to execute the program. The device will also automatically run a program on power up.

note

The commands run, list, and new are never recorded! They are used to handle the recorded program.

Go ahead and enter $ and press the enter key.

Add three lines of print commands. Nothing will get executed as those commands are getting stored internally, not executed. When finished, use list to see the commands.

Use run to run the program.

Add another command to the list then try to run again.

use new to erase the program. Verify the program is removed using list.

note

It is not possible to modify individual lines once recorded. This is not a problem when using the Console as it sends the program complete in one shot.

We can run a program that runs indefinitely using loops.

@Loop
Print("Hello")
Print(" world")
Print(" 123!!")
goto Loop

A running program can be terminated by hitting the ESC key, DEL Key, or Backspace Key. Hit escape, then 'new' to erase the program. verify using 'list'.

Recording programs are either used to run the module Standalone or to extend the module's functionality. We call this Hybrid Mode.

Hybrid Mode

There is no Hybrid Mode exactly, but you can combine both immediate and record modes to extend the system with additional commands. Say we want to extend the system with a Hello() function. We can record this extension that can be executed immediately.

Enter recoding mode then start a new program. Then Enter this program:

fn Hello(b1)
Print("Hello ")
Println(b1)
fend

Now, list the program to make sure it was recorded properly.

Switch to immediate mode and enter Hello("John Due").

This is exactly how hundreds of modules provide user-friendly drivers. They all have a recorded script that handles module-specific tasks. Then these drivers commands can be executed from a Supported System over one of the Interfaces.

Asynchronous Immediate

When the system in 'run' mode, running a loop, it is possible to inject other code to run asynchronously. Use asio(1) to enable this feature.

Consider this program that loops and print the global variable _x every 500ms.

asio(1)
while 1
println(_x)
wait(500)
wend

With Asynchronous immediate enabled, we can now inject _x=5 at any time to change the output to 5.

This can also be used to call functions and even run loops! Any valid single-line commands can be injected asynchronously.

This is a simple program that prints whatever is in a1 every 500ms.

asio(1)
fn SetA1(a2)
a1 = a2
fend

SetA1("Hello")

while 1
println(a1)
wait(500)
wend

Now we can inject SetA1("DUELink"). Of course, you can just do a1[]="Try it" but we used a function to show the possibilities.