How do you split data from BlueTooth to create a list?

MIT App Inventor Help
1

I am facing with a problem to split data in a list which comes from BlueTooth in the following format:data are 24 characters hexa each, the transmiiter can send one, two, trhee or more data in a package, however each data has CR at its end. Something like [ABCD..1,ABCD...2,ABCD...3,....], [EF01...1,EF02...2]... at the end of data are sent CR signal.
I receive the message by implementing the following blocks:

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ABCD...1
ABCD...2
ABCD...3

EF01...1
EF02...2

and so on

For each data received in each package(array), such data are treated as one single item in the list. I woud like to split each single data of each package in its specific list item. They are being agrupped at the same list item.

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Even if i split at "\r", as per the blocks attached, the same occurs inside the list "(" and ")" for each package of data, like the following:
(ABCD..1
ABCD..2
ABCD..3)

(EF01..1
EF02..2)

Thanks for any help.

2

You are using \r as a delimiter.
Most people use \n.

Here's the standard advice for those people, which you can adapt or implement.

Be sure to use println() at the end of each message to send from the sending device, to signal end of message.

Only use print() in the middle of a message.

Be sure not to println() in the middle of a message, or you will break it into two short messages and mess up the item count after you split the message in AI2.

Do not rely on timing for this, which is unreliable.

In the AI2 Designer, set the Delimiter attribute of the BlueTooth Client component to 10 to recognize the End of Line character.
BlueToothClient1_Properties
Also, return data is not immediately available after sending a request,
you have to start a Clock Timer repeating and watch for its arrival in the Clock Timer event. The repeat rate of the Clock Timer should be faster than the transmission rate in the sending device, to not flood the AI2 buffers.

In your Clock Timer, you should check

  Is the BlueTooth Client still Connected?
  Is Bytes Available > 0?
     IF Bytes Available > 0 THEN
       set message var  to BT.ReceiveText(-1)

This takes advantage of a special case in the ReceiveText block:

ReceiveText(numberOfBytes)
Receive text from the connected Bluetooth device. If numberOfBytes is less than 0, read until a delimiter byte value is received.

If you are sending multiple data values per message separated by | or comma, have your message split into a local or global variable for inspection before trying to select list items from it. Test if (length of list(split list result) >= expected list length) before doing any select list item operations, to avoid taking a long walk on a short pier. This bulletproofing is necessary in case your sending device sneaks in some commentary messages with the data values.

Some people send temperature and humidity in separate messages with distinctive prefixes like "t:" (for temperature) and "h:" (for humidity).
(That's YAML format.)

The AI2 Charts component can recognize these and graph them. See Bluetooth Client Polling Rate - #12 by ABG

To receive YAML format messages, test if the incoming message contains ':' . If true, split it at ':' into a list variable, and find the prefix in item 1 and the value in item 2.

For more customized advice, post the code that generates the messages and the exported aia file.

3

More customized comments:

If you are using commas between data in each message, the List Picker and List View components can recognize those directly through their ElementsFromString block.

So just dump the incoming message into that part of the ListPicker/Viewer and you're good to go.

If you don't like parentheses() in your lists, switch to JSON format in Project Properties.

Also, what looks like a list in text is not a list until it comes out of a block that creates lists.

4

I implemented the code as per your suggestion related to the Clock Timer. If i put BT.ReceiveText as equal -1, AI2 stops and i need to restart. I added about 10, 20 to the BT Delimiter Byte and Clock time is about 5 ms. Any idea why AI2 stops? Thank you for your help.

5

Export and upload your .aia file here.

Also include your sketch code.