# \[SOLVED\] Difficulty Receiving Strings Over Bluetooth

**URL:** <https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073>\
**Category:** BLE / BlueTooth\
**Created:** [April 19, 2025, 7:08pm UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073 "2025-04-19T19:08:06Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![4001.group16zwb6dn](https://avatars.discourse-cdn.com/v4/letter/4/b77776/32.png) [@4001.group16zwb6dn](https://community.thunkable.com/u/4001.group16zwb6dn)\
**Post date:** [April 19, 2025, 7:08pm UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073/1 "2025-04-19T19:08:06Z")

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Hello,

I am trying to receive 4 numbers in Thunkable through BLE. I send all 4 values in 1 string, separated by commas. The string is read properly on nRF Connect, and the Arduino code is attached. I’m confident that the device and app are connected. In Thunkable, the ‘receive string’ block returns an error that says “undefined is not a function”, and I’m not sure what that means. If I include the blocks currently greyed out, the ‘Make list from text’ line crashes the app.

I’ve also tried using the ‘when characteristics change’ block (seen in the whole app screenshot), but that condition is never even triggered, despite the characteristics being changed frequently in the Arduino code.

How should I be reading in and parsing this string?

 ![refresh function](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/f/1/f1e843930e7badefec2816956133d8fcd887d901.png)  
 ![error_msg](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/6/2/62ba10909dd76bb69fdafcbf15a6a397f4e67d58.jpeg)  
 ![Thunkable app](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/9/9/9967d19fb624425b17bd9f2eb42d7a7ae7e57588.png)  
 ![arduino code](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/2/5/2596d2985dd2ddf513936654da55ed767289cf91.png)

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**Author:** ![ioannis](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/ioannis/32/146956_2.png) [@ioannis](https://community.thunkable.com/u/ioannis)\
**Post date:** [April 20, 2025, 5:33am UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073/2 "2025-04-20T05:33:25Z")

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Hello @4001.group16zwb6dn  
Based on your screenshot, it doesn’t transmit strings; it broadcasts strings (notify method).  
This means that you will need to use the BLE blocks [“Subscribe To Characteristics” and “Characteristics Change”](https://docs.thunkable.com/blocks/advanced-app-features/bluetooth-low-energy#subscribe-to-characteristics) to subscribe to peripheral device’s characteristics and receiving data.

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**Author:** ![4001.group16zwb6dn](https://avatars.discourse-cdn.com/v4/letter/4/b77776/32.png) [@4001.group16zwb6dn](https://community.thunkable.com/u/4001.group16zwb6dn)\
**Post date:** [April 21, 2025, 5:12pm UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073/3 "2025-04-21T17:12:06Z")

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Hi ioannis,

That’s helpful to know, thank you. I’m still running into trouble when using the “Characteristics Change” block. Despite the characteristics changing, the block never triggers. Do you know why this might be happening?

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**Author:** ![4001.group16zwb6dn](https://avatars.discourse-cdn.com/v4/letter/4/b77776/32.png) [@4001.group16zwb6dn](https://community.thunkable.com/u/4001.group16zwb6dn)\
**Post date:** [April 21, 2025, 6:04pm UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073/4 "2025-04-21T18:04:10Z")

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The error was found!!! I was creating a new UUID for the characteristic, on the Arduino side. The UUID when creating the characteristic needs to be the same as the service UUID.

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**Author:** ![ioannis](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/ioannis/32/146956_2.png) [@ioannis](https://community.thunkable.com/u/ioannis)\
**Post date:** [April 21, 2025, 6:44pm UTC](https://community.thunkable.com/t/solved-difficulty-receiving-strings-over-bluetooth/3755073/5 "2025-04-21T18:44:25Z")

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