Error 4101: Invalid Chart Entry Value(s). Bluetooth Line Graph


I am working on an ECG project and the application displays the Bluetooth data, however, there is always a message on the screen with Error 4101. The error pops up for a few seconds and is then followed by another Error4101. What does this mean and how can this issue be resolved?

I have included pictures of the Errors and my relevant blocks. (Blocks not included are for Bluetooth permission and connection.)

Kind regards

Just to clarify, the data is being plotted, but also displays Error 4101.

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.
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:

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.


Thanks for your reply. I have uploaded a copy of my code, is the println() possibly causing an issue as it is not at the end?

ecg.ino (1.5 KB)

Regarding the YAML format, if serial0.print("t:"); is inserted into the code will this help with providing real-time data, or not make much of a difference? And would that help with the 4101 error?


I have changed the blocks to what you mentioned, and the error 4101 occurs less frequently, however the graph glitches every few seconds as shown in the video attached, do you know how to fix this issue.

Setting the range in the clock timer might be causing the glitch.

You only need to do that once.

Also give some thought to limitting the number of entries in the graph.

Also, be sure to read faster than you write, or the AI2 Bluetooth buffer will fill.

Thanks again for your help, I have changed the range into the initialise screen block and the line issue shown in the video still occurs, less frequently, and error 4101 still occurs. What is the meaning of this error 4101?

The errors that usually come up contain numbers like: ".-3.91", "1 124" "2 2-2.43"where a decimal point occurs twice, or space in the middle of numbers or negative sign in the middle of a number. Do you know the cause of this issue?

Kind regards

Show us where you set the BlueTooth Delimiter to 10 in your app.

Thanks for your comment. I have uploaded a picture of BluetoothClient and an updated view of my blocks.

Kind regards

I suspect println of a float is generating and trying to send strings longer than the Bluetooth length limit of 20 bytes.

Search this board for logger code to capture the traffic and display it.

You might need to learn how to use sprintf