Thanks for respond. Can we detect which device will work or not, any tip for that ?

Saw that you are an Android developer 👍
If you want to debug this, play around with the options in this class:

https://github.com/d4rken-org/capod/blob/main/app-common/src/main/java/eu/darken/capod/common/bluetooth/BleScanner.kt

On affected devices the callback either does not return or returns empty lists:

capod/app-common/src/main/java/eu/darken/capod/common/bluetooth/BleScanner.kt

Lines 71 to 96 in cea8f22

    
           val callback = object : ScanCallback() { 
        
               var lastScanAt = System.currentTimeMillis() 
        
               override fun onScanResult(callbackType: Int, result: ScanResult) { 
        
                   log(TAG, VERBOSE) { 
        
                       val delay = System.currentTimeMillis() - lastScanAt 
        
                       lastScanAt = System.currentTimeMillis() 
        
                       "onScanResult(delay=${delay}ms, callbackType=$callbackType, result=$result)" 
        
                   } 
        
                   trySend(filterResults(setOf(result))) 
        
               } 
        
               override fun onBatchScanResults(results: MutableList<ScanResult>) { 
        
                   log(TAG, VERBOSE) { 
        
                       val delay = System.currentTimeMillis() - lastScanAt 
        
                       lastScanAt = System.currentTimeMillis() 
        
                       "onBatchScanResults(delay=${delay}ms, results=$results)" 
        
                   } 
        
                   trySend(filterResults(results)) 
        
               } 
        
               override fun onScanFailed(errorCode: Int) { 
        
                   log(TAG, WARN) { "onScanFailed(errorCode=$errorCode)" } 
        
               } 
        
           }

On some devices, changing the API call to NOT use batch mode fixes the issue. On others it only works in batchmode.

Reading some forums and bug reports on Google, there are some devices where the Bluetooth chip doesn't support a specific BLE scan hardware modes and the ROM devs tried to fake it in software and their solution is buggy.

Maybe you can find another workaround?

	val callback = object : ScanCallback() {
	var lastScanAt = System.currentTimeMillis()
	override fun onScanResult(callbackType: Int, result: ScanResult) {
	log(TAG, VERBOSE) {
	val delay = System.currentTimeMillis() - lastScanAt
	lastScanAt = System.currentTimeMillis()
	"onScanResult(delay=${delay}ms, callbackType=$callbackType, result=$result)"
	}

	trySend(filterResults(setOf(result)))
	}

	override fun onBatchScanResults(results: MutableList<ScanResult>) {
	log(TAG, VERBOSE) {
	val delay = System.currentTimeMillis() - lastScanAt
	lastScanAt = System.currentTimeMillis()
	"onBatchScanResults(delay=${delay}ms, results=$results)"
	}

	trySend(filterResults(results))
	}

	override fun onScanFailed(errorCode: Int) {
	log(TAG, WARN) { "onScanFailed(errorCode=$errorCode)" }
	}
	}

Uh oh!

Device not visible #124

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