Bad arguments to <= error observed

[Ravi_Kumar1]

Hi All,

I am reading the Tepmerature data via Blutooth...after multiple reads getting the below error...

Bad arguments to <=
The operation <= cannot accept the arguments:, ["?rV?'],[28]

Thanks,
Ravi Kumar.

[Spicy_Topics]

Check the local variable cels value

Instead of number it receives some text it seems

[dora_paz]

Error comes from this block

Your temperature text is "?rV?" and math blocks "hates" empty or text strings

You can avoid such error like this

[Ravi_Kumar1]

Thanks for the info.

some time...even getting the below error...

Select list item: List index too large

Select list item : Attempt to get item number 2 of a list of length 1:["90.27"]

So the problem should be....reading data from Arduni Uno in string right ?

[Ravi_Kumar1]

Shall we covert string to Integer in MIT app ?

[ABG]

This looks like a standard BlueTooth Text Delimiter problem.

Here is the standard advice:

Please see the Delimiter article in FAQ

FAQ Section: Bluetooth < version 4 (BlueTooth Client) and Arduino

Arduino HC-06 tutorials Arduino USB - Pavitra and Thunkable Arduino via USB Delimiter usage for receiving one message per ReadText DHT22 Temperature or Humidity, no Clock - kio4.com How to send CR the hard way http://www.martyncurrey.com/android-mit-app-inventor-auto-connect-to-bluetooth/ Instructables YouTube course on Arduino/AI2 - Magesh Jayakumar Martyn Arduino Bluetooth sketch Sending Slider Data to Arduino - Neil Kenyon Turning a LED on and off with an Arduino, a HC-06 and Andr…

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

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.

[ChrisWard]

@Ravi_Kumar1

Shall we covert string to Integer in MIT app ?

That's already automatic.

[ChrisWard]

In Receive Text block, the number of bytes to receive should be set to -1 (maths block). This ensures that all available bytes are loaded.

After the code splits the data, test the list length.

Example:

Your uploaded screenshots are difficult to read. Use App Inventor to make them.
Right-mouse in the Blocks work area and select "Download Blocks as image"