Instead of showing the value, � symbol appears

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The Bluetooth module is this one. The connection is well made because the symbols react when I spin the potentiometer, but the symbols still appear.

Screenshot_2025-01-09-20-39-35-035_com.google.android.googlequicksearchbox-edit
Screenshot_2025-01-09-20-39-35-035_com.google.android.googlequicksearchbox-edit965×975 113 KB

How to fix too large index