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feat: prefer CR5L BLE characteristics on macOS #207

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d62a9cd
feat: prefer CR5L BLE characteristics on macOS
Apr 12, 2026
02a1eaf
fix: address CR5L BLE bridge review feedback
Apr 16, 2026
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134 changes: 114 additions & 20 deletions packages/libdivecomputer_plugin/darwin/Sources/LibDCDarwin/BleIoStream.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,15 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
private static let pelagicGen1TxCharacteristic = CBUUID(
string: "6606AB42-89D5-4A00-A8CE-4EB5E1414EE0"
)
private static let nordicUartServiceUUID = CBUUID(
string: "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
)
private static let nordicUartServiceRxCharacteristic = CBUUID(
string: "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
)
private static let nordicUartServiceNotifyCharacteristic = CBUUID(
string: "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"
)
private static let notifySettleDelaySeconds: TimeInterval = 0.3
private static let bleIoctlType: UInt32 = UInt32(Character("b").asciiValue!)
private static let bleIoctlGetNameNumber: UInt32 = 0
Expand All @@ -44,13 +53,16 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
private let centralManager: CBCentralManager

private var writeCharacteristic: CBCharacteristic?
// Kept only for the "Discovery ready" log message.
private var notifyCharacteristic: CBCharacteristic?
private var subscribedCharacteristics: [CBCharacteristic] = []
Comment thread
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private var bestCandidate: CharacteristicCandidate?
private var remainingServiceDiscoveries = 0
private var discoverySignaled = false

private let readLock = NSLock()
private var readBuffer = Data()
private var readPackets: [Data] = []
private var partialReadBuffer = Data()
private let readSemaphore = DispatchSemaphore(value: 0)
private let writeSemaphore = DispatchSemaphore(value: 0)
private let writeReadySemaphore = DispatchSemaphore(value: 0)
Expand All @@ -74,6 +86,11 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
/// Set by DiveComputerHostApiImpl before download starts.
var onPinCodeRequired: ((String) -> Void)?

private var isLikelyCrestDevice: Bool {
let name = peripheral.name?.uppercased() ?? ""
return name.hasPrefix("CREST")
}

init(peripheral: CBPeripheral, centralManager: CBCentralManager) {
self.peripheral = peripheral
self.centralManager = centralManager
Expand Down Expand Up @@ -138,6 +155,7 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
bestCandidate = nil
writeCharacteristic = nil
notifyCharacteristic = nil
subscribedCharacteristics = []
hasSeenNotify = false
writeWithoutResponsePreferred = false
consecutiveReadTimeouts = 0
Expand Down Expand Up @@ -261,9 +279,9 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
private static let cPoll: libdc_io_poll_fn = { userdata, timeout in
let stream = Unmanaged<BleIoStream>.fromOpaque(userdata!).takeUnretainedValue()
stream.readLock.lock()
let available = stream.readBuffer.count
let available = !stream.partialReadBuffer.isEmpty || !stream.readPackets.isEmpty
stream.readLock.unlock()
if available > 0 { return Int32(LIBDC_STATUS_SUCCESS) }
if available { return Int32(LIBDC_STATUS_SUCCESS) }

if timeout == 0 { return Int32(LIBDC_STATUS_TIMEOUT) }

Expand All @@ -286,13 +304,25 @@ class BleIoStream: NSObject, CBPeripheralDelegate {

while true {
readLock.lock()
let available = readBuffer.count
if available > 0 {
let bytesToRead = min(size, readBuffer.count)
_ = readBuffer.withUnsafeBytes { ptr in
if partialReadBuffer.isEmpty, !readPackets.isEmpty {
partialReadBuffer = readPackets.removeFirst()
}
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if partialReadBuffer.count > size {
let packetSize = partialReadBuffer.count
partialReadBuffer.removeAll(keepingCapacity: true)
readLock.unlock()
actual.pointee = 0
NativeLogger.e("BleIoStream", category: "BLE",
"Received BLE packet larger than requested read size"
+ " (packet=\(packetSize) requested=\(size)); dropping packet")
return Int32(LIBDC_STATUS_IO)
}
if !partialReadBuffer.isEmpty {
let bytesToRead = min(size, partialReadBuffer.count)
_ = partialReadBuffer.withUnsafeBytes { ptr in
memcpy(data, ptr.baseAddress!, bytesToRead)
}
readBuffer.removeFirst(bytesToRead)
partialReadBuffer.removeFirst(bytesToRead)
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readLock.unlock()
actual.pointee = bytesToRead
return Int32(LIBDC_STATUS_SUCCESS)
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Expand Down Expand Up @@ -392,7 +422,8 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
}

readLock.lock()
readBuffer.removeAll(keepingCapacity: true)
readPackets.removeAll(keepingCapacity: true)
partialReadBuffer.removeAll(keepingCapacity: true)
readLock.unlock()
drainSemaphore(readSemaphore)
return Int32(LIBDC_STATUS_SUCCESS)
Expand Down Expand Up @@ -431,6 +462,11 @@ class BleIoStream: NSObject, CBPeripheralDelegate {

private func initialWriteWithoutResponsePreference(for characteristic: CBCharacteristic) -> Bool {
let properties = characteristic.properties
// CR5L needs the NUS path to stay Crest-gated. If we later want to
// generalize support for more NUS devices, start by widening this gate.
if isLikelyCrestDevice && characteristic.uuid == Self.nordicUartServiceRxCharacteristic {
return false
}
if characteristic.uuid == Self.pelagicGen1TxCharacteristic {
return true
}
Expand Down Expand Up @@ -626,18 +662,25 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
+ " \(error.localizedDescription)")
return
}
if let notify = notifyCharacteristic, characteristic.uuid != notify.uuid {
guard subscribedCharacteristics.contains(where: { $0.uuid == characteristic.uuid }) else {
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NativeLogger.w("BleIoStream", category: "BLE",
"Ignoring notify from \(characteristic.uuid.uuidString)"
+ " (subscribed count=\(subscribedCharacteristics.count))")
return
}
guard let value = characteristic.value, !value.isEmpty else {
NativeLogger.w("BleIoStream", category: "BLE",
"Ignoring empty notify from \(characteristic.uuid.uuidString)")
return
}
guard let value = characteristic.value else { return }
hasSeenNotify = true
consecutiveReadTimeouts = 0
NativeLogger.d("BleIoStream", category: "BLE",
"notify \(characteristic.uuid.uuidString)"
+ " bytes=\(value.count)"
+ " data=\(Self.hexString(value, maxBytes: Self.maxLogBytes))")
readLock.lock()
readBuffer.append(value)
readPackets.append(value)
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readLock.unlock()
readSemaphore.signal()
}
Expand All @@ -660,29 +703,37 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
func peripheral(_ peripheral: CBPeripheral,
didUpdateNotificationStateFor characteristic: CBCharacteristic,
error: Error?) {
guard let notify = notifyCharacteristic, characteristic.uuid == notify.uuid else {
guard subscribedCharacteristics.contains(where: { $0.uuid == characteristic.uuid }) else {
return
}
guard waitingForNotifyEnable else { return }
waitingForNotifyEnable = false

if let error {
let pendingCount = subscribedCharacteristics.filter { !$0.isNotifying }.count
NativeLogger.e("BleIoStream", category: "BLE",
"Failed enabling notify for \(characteristic.uuid.uuidString):"
+ " \(error.localizedDescription)")
+ " \(error.localizedDescription)"
+ " (pending=\(pendingCount))")
waitingForNotifyEnable = false
signalDiscoveryReady()
return
}
if !characteristic.isNotifying {
let pendingCount = subscribedCharacteristics.filter { !$0.isNotifying }.count
NativeLogger.w("BleIoStream", category: "BLE",
"Notify not active for \(characteristic.uuid.uuidString)")
"Notify not active for \(characteristic.uuid.uuidString)"
+ " (pending=\(pendingCount))")
waitingForNotifyEnable = false
signalDiscoveryReady()
return
}
NativeLogger.d("BleIoStream", category: "BLE",
"Notify enabled for \(characteristic.uuid.uuidString)")
isReady = true
signalDiscoveryReady()
if subscribedCharacteristics.allSatisfy(\.isNotifying) {
waitingForNotifyEnable = false
isReady = true
signalDiscoveryReady()
}
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}

private func signalDiscoveryReady() {
Expand All @@ -703,6 +754,9 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
if props.contains(.writeWithoutResponse) { writeScore += 4 }
if props.contains(.write) { writeScore += 2 }
if Self.preferredWriteUUIDs.contains(characteristic.uuid) { writeScore += 1000 }
if isLikelyCrestDevice && characteristic.uuid == Self.nordicUartServiceRxCharacteristic {
writeScore += 1000
}
if bestWrite == nil || writeScore > bestWrite!.score {
bestWrite = (characteristic, writeScore)
}
Expand All @@ -713,6 +767,11 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
if props.contains(.notify) { notifyScore += 4 }
if props.contains(.indicate) { notifyScore += 2 }
if Self.preferredNotifyUUIDs.contains(characteristic.uuid) { notifyScore += 1000 }
if isLikelyCrestDevice &&
characteristic.uuid == Self.nordicUartServiceNotifyCharacteristic
{
notifyScore += 1000
}
if bestNotify == nil || notifyScore > bestNotify!.score {
bestNotify = (characteristic, notifyScore)
}
Expand All @@ -727,6 +786,9 @@ class BleIoStream: NSObject, CBPeripheralDelegate {
if Self.preferredServiceUUIDs.contains(service.uuid) {
serviceScore += 1000
}
if isLikelyCrestDevice && service.uuid == Self.nordicUartServiceUUID {
serviceScore += 1000
}

if let existing = bestCandidate, existing.score >= serviceScore {
return
Expand All @@ -749,23 +811,55 @@ class BleIoStream: NSObject, CBPeripheralDelegate {

writeCharacteristic = candidate.write
notifyCharacteristic = candidate.notify
let serviceCharacteristics = candidate.write.service?.characteristics ?? []
if isLikelyCrestDevice && candidate.write.uuid == Self.nordicUartServiceRxCharacteristic {
subscribedCharacteristics = serviceCharacteristics.filter {
$0.properties.contains(.notify) || $0.properties.contains(.indicate)
}
if subscribedCharacteristics.isEmpty {
let writeService = candidate.write.service?.uuid.uuidString ?? "nil"
let notifyService = candidate.notify.service?.uuid.uuidString ?? "nil"
NativeLogger.w("BleIoStream", category: "BLE",
"NUS write characteristic found but no notify/indicate characteristics"
+ " on its service (writeService=\(writeService));"
+ " falling back to candidate.notify=\(candidate.notify.uuid.uuidString)"
+ " (notifyService=\(notifyService))")
subscribedCharacteristics = [candidate.notify]
}
if candidate.notify.service !== candidate.write.service {
let writeService = candidate.write.service?.uuid.uuidString ?? "nil"
let notifyService = candidate.notify.service?.uuid.uuidString ?? "nil"
NativeLogger.w("BleIoStream", category: "BLE",
"Selected write/notify characteristics from different services"
+ " for Crest/NUS path"
+ " (writeService=\(writeService)"
+ " notifyService=\(notifyService))")
}
} else {
subscribedCharacteristics = [candidate.notify]
}
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writeWithoutResponsePreferred = initialWriteWithoutResponsePreference(for: candidate.write)
NativeLogger.d("BleIoStream", category: "BLE",
"Selected write=\(candidate.write.uuid.uuidString)"
+ " (\(Self.propertySummary(candidate.write.properties)))"
+ " notify=\(candidate.notify.uuid.uuidString)"
+ " (\(Self.propertySummary(candidate.notify.properties)))"
+ " (score=\(candidate.score))")
NativeLogger.d("BleIoStream", category: "BLE",
"Subscribed characteristics:"
+ " \(subscribedCharacteristics.map { $0.uuid.uuidString }.joined(separator: ","))")
NativeLogger.d("BleIoStream", category: "BLE",
"Initial write mode preference:"
+ " \(writeWithoutResponsePreferred ? "withoutResponse" : "withResponse")")
if candidate.notify.isNotifying {
if !subscribedCharacteristics.isEmpty && subscribedCharacteristics.allSatisfy(\.isNotifying) {
isReady = true
signalDiscoveryReady()
return
}
waitingForNotifyEnable = true
peripheral.setNotifyValue(true, for: candidate.notify)
for characteristic in subscribedCharacteristics where !characteristic.isNotifying {
peripheral.setNotifyValue(true, for: characteristic)
}
}
}

Expand Down
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