SulTee/SulTee/BLEManager.swift

@@ -68,14 +68,21 @@ final class BLEManager: NSObject, ObservableObject {
     func sendGPS(_ data: Data) {
         guard gpsStreamEnabled, isConnected,
               let p = peripheral, let c = gpsChar else { return }
-        p.writeValue(data, for: c, type: .withoutResponse)
+        // Use writeWithoutResponse if the characteristic supports it (lower latency,
+        // no ACK overhead).  Fall back to write-with-response if the firmware only
+        // advertises PROPERTY_WRITE (0x08) — e.g. NimBLE default without WRITE_NR.
+        let writeType: CBCharacteristicWriteType =
+            c.properties.contains(.writeWithoutResponse) ? .withoutResponse : .withResponse
+        p.writeValue(data, for: c, type: writeType)
     }
 
     /// Write a pre-built IMU packet to the tag.  Call at 10 Hz.
     func sendIMU(_ data: Data) {
         guard imuStreamEnabled, isConnected,
               let p = peripheral, let c = imuChar else { return }
-        p.writeValue(data, for: c, type: .withoutResponse)
+        let writeType: CBCharacteristicWriteType =
+            c.properties.contains(.writeWithoutResponse) ? .withoutResponse : .withResponse
+        p.writeValue(data, for: c, type: writeType)
     }
 
     // MARK: - Internal helpers

SulTee/SulTee/BLEPackets.swift

@@ -164,25 +164,3 @@ private extension Data {
     }
 }
 
-// MARK: - Safe integer clamping
-
-private extension Int16 {
-    init(clamping value: Int64) {
-        self = Int16(max(Int64(Int16.min), min(Int64(Int16.max), value)))
-    }
-}
-private extension Int32 {
-    init(clamping value: Int64) {
-        self = Int32(max(Int64(Int32.min), min(Int64(Int32.max), value)))
-    }
-}
-private extension UInt16 {
-    init(clamping value: Int64) {
-        self = UInt16(max(Int64(0), min(Int64(UInt16.max), value)))
-    }
-}
-private extension UInt8 {
-    init(clamping value: Int64) {
-        self = UInt8(max(Int64(0), min(Int64(UInt8.max), value)))
-    }
-}

SulTee/SulTee/BLEStatusView.swift

@@ -70,7 +70,7 @@ struct BLEStatusView: View {
 
     private var streamingSection: some View {
         Section("Data Streaming") {
-            Toggle(isOn: $sensor.ble.gpsStreamEnabled) {
+            Toggle(isOn: Binding(get: { ble.gpsStreamEnabled }, set: { ble.gpsStreamEnabled = $0 })) {
                 Label {
                     VStack(alignment: .leading, spacing: 2) {
                         Text("GPS → Tag")
@@ -82,7 +82,7 @@ struct BLEStatusView: View {
                         .foregroundStyle(.blue)
                 }
             }
-            Toggle(isOn: $sensor.ble.imuStreamEnabled) {
+            Toggle(isOn: Binding(get: { ble.imuStreamEnabled }, set: { ble.imuStreamEnabled = $0 })) {
                 Label {
                     VStack(alignment: .leading, spacing: 2) {
                         Text("IMU → Tag")

SulTee/SulTee/SensorManager.swift

@@ -229,7 +229,7 @@ final class SensorManager: NSObject, ObservableObject {
         locationManager.startUpdatingLocation()
         locationManager.startUpdatingHeading()
         if !motionManager.isDeviceMotionActive { startIMU() }
-        if !altimeter.isRelativeAltitudeAvailable() == false { startBarometer() }
+        if CMAltimeter.isRelativeAltitudeAvailable() { startBarometer() }
     }
 
     private func stopSensors() {