ESP32 Bluetooth send integer

MIT App Inventor Help
,
1

Hello

I am trying to send an integer (or other typ of non 8bit number) via BT to my Android phone. But I was not successful.

Here is my ESP32 Code (shortened):

int number = 205;

void setup(void) {

SerialBT.begin("ESP32_Sensor");

}

void loop() {

SerialBT.write(number);

delay(10);

}

That is my App code:

image
image1370×726 83.9 KB

I tried it with 1,2 and 4 ByteNumber, but no luck.
I have also tried it with SerialBT.print() but regardless of what I tried I always get a wrong number. There I have tried it with the textblock as well

Has anyone an Idea?

Thanks

2

Knowing what number arrived could help diagnose the problem.

3

Use ReceiveUnsigned1Byte blocks instead of ReceiveSigned1Byte...

You send the number 205 and it is already a negative number if you receive with a sign.

1 Like
4

Hello.
What about receiving 2551 large number?
How do you put blocks together for that.
I am having big trouble with that.

5

You want send the number 2551?

Send it as text

6

Sorry ... this number what I wrote was random and it represent digital value of voltage.
I just wanna send one voltage reading and show it in MIT app inventor like volt meter.
I just found this MIT app inventor a couple of days ago so it is all new to me.
So I will try to do the simpliest volt meter.

7

Here is a simple BlueTooth text receiver sample, for single value per line:
blocks
initialize global message to

when Clock1 .Timer do
when Clock1 .Timer do1290×410 59.1 KB

when Screen1 .Initialize do
when Screen1 .Initialize do814×182 22.9 KB

8

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.