Hi Everyone! I am receiving two values (of voltage and current) as a text at the same time and then, using indexing, I am separating those values into two separate lists (One list for all the voltages and the other list for all the currents). Now I want to plot the Graph between these lists (V-I Graph). But there is an error as I am getting a list of numbers behaving as a string. Please tell me how can I convert these lists (of strings) into a numbers list so I can plot a graph. I tried some solutions from the MIT APP INVENTOR community but still have not managed to get my objective.
here is the list I am getting
And here is the output that I am receiving from Arduino through bluetooth
Two more things are needed to diagnose this:
- Your Arduino code, so we can see how you format your messages, and
- Your Designer, so we can correlate your screen grab with your Labels.
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In the above figure, we define a function "getCurrent" and return the value to the main function. Similar case with the voltage function described below.
Then, sending those values through Bluetooth module.
Anything Else?
I see a discrepancy between how you are sending your voltage and current vs how your AI2 blocks pick out the voltage and current from the incoming messages.
Your AI2 blocks expect to see a '|' between the voltage and current, but you just send a space between them in the Arduino code.
Also, I see a print(voltage) in the get_Voltage routine, after the return.
Is this never reached because of the return, and just there to mislead?
Any way, it is poor practice to print from subprocedures and from the calling code, making extra work for who ever has to envision the outgoing data stream..
Here is the standard practice for you to check:
Please see the Delimiter article in FAQ
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.