diff --git a/controls-core/src/commonMain/kotlin/space/kscience/controls/manager/DeviceManager.kt b/controls-core/src/commonMain/kotlin/space/kscience/controls/manager/DeviceManager.kt
index 871f236..cc043c7 100644
--- a/controls-core/src/commonMain/kotlin/space/kscience/controls/manager/DeviceManager.kt
+++ b/controls-core/src/commonMain/kotlin/space/kscience/controls/manager/DeviceManager.kt
@@ -37,12 +37,7 @@ public class DeviceManager : AbstractPlugin(), DeviceHub {
     }
 }
 
-
-/**
- * Register and start a device built by [factory] with current [Context] and [meta].
- */
-public fun <D : Device> DeviceManager.install(name: String, factory: Factory<D>, meta: Meta = Meta.EMPTY): D {
-    val device = factory(meta, context)
+public fun <D : Device> DeviceManager.install(name: String, device: D): D {
     registerDevice(NameToken(name), device)
     device.launch {
         device.open()
@@ -50,6 +45,13 @@ public fun <D : Device> DeviceManager.install(name: String, factory: Factory<D>,
     return device
 }
 
+
+/**
+ * Register and start a device built by [factory] with current [Context] and [meta].
+ */
+public fun <D : Device> DeviceManager.install(name: String, factory: Factory<D>, meta: Meta = Meta.EMPTY): D =
+    install(name, factory(meta, context))
+
 /**
  * A delegate that initializes device on the first use
  */
diff --git a/controls-core/src/commonMain/kotlin/space/kscience/controls/spec/DevicePropertySpec.kt b/controls-core/src/commonMain/kotlin/space/kscience/controls/spec/DevicePropertySpec.kt
index 078a43d..0e72fca 100644
--- a/controls-core/src/commonMain/kotlin/space/kscience/controls/spec/DevicePropertySpec.kt
+++ b/controls-core/src/commonMain/kotlin/space/kscience/controls/spec/DevicePropertySpec.kt
@@ -2,10 +2,7 @@ package space.kscience.controls.spec
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.flow.filter
-import kotlinx.coroutines.flow.filterIsInstance
-import kotlinx.coroutines.flow.launchIn
-import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.*
 import kotlinx.coroutines.launch
 import space.kscience.controls.api.ActionDescriptor
 import space.kscience.controls.api.Device
@@ -105,19 +102,31 @@ public operator fun <T, D : Device> D.set(propertySpec: WritableDevicePropertySp
     write(propertySpec, value)
 }
 
+/**
+ * A type safe flow of property changes for given property
+ */
+public fun <D : Device, T> D.propertyFlow(spec: DevicePropertySpec<D, T>): Flow<T> = messageFlow
+    .filterIsInstance<PropertyChangedMessage>()
+    .filter { it.property == spec.name }
+    .mapNotNull { spec.converter.metaToObject(it.value) }
+
 /**
  * A type safe property change listener. Uses the device [CoroutineScope].
  */
-public fun <D : Device, T> Device.onPropertyChange(
+public fun <D : Device, T> D.onPropertyChange(
     spec: DevicePropertySpec<D, T>,
-    callback: suspend PropertyChangedMessage.(T?) -> Unit,
+    callback: suspend PropertyChangedMessage.(T) -> Unit,
 ): Job = messageFlow
     .filterIsInstance<PropertyChangedMessage>()
     .filter { it.property == spec.name }
     .onEach { change ->
-        change.callback(spec.converter.metaToObject(change.value))
+        val newValue = spec.converter.metaToObject(change.value)
+        if (newValue != null) {
+            change.callback(newValue)
+        }
     }.launchIn(this)
 
+
 /**
  * Reset the logical state of a property
  */
diff --git a/controls-pi/build.gradle.kts b/controls-pi/build.gradle.kts
index 3fa0dbc..b269c85 100644
--- a/controls-pi/build.gradle.kts
+++ b/controls-pi/build.gradle.kts
@@ -5,8 +5,8 @@ plugins {
 
 dependencies{
     api(project(":controls-core"))
-    implementation("com.pi4j:pi4j-ktx:2.4.0") // Kotlin DSL
-    implementation("com.pi4j:pi4j-core:2.3.0")
-    implementation("com.pi4j:pi4j-plugin-raspberrypi:2.3.0")
-    implementation("com.pi4j:pi4j-plugin-pigpio:2.3.0")
+    api("com.pi4j:pi4j-ktx:2.4.0") // Kotlin DSL
+    api("com.pi4j:pi4j-core:2.3.0")
+    api("com.pi4j:pi4j-plugin-raspberrypi:2.3.0")
+    api("com.pi4j:pi4j-plugin-pigpio:2.3.0")
 }
\ No newline at end of file
diff --git a/controls-pi/src/main/kotlin/space/kscience/controls/pi/PiPlugin.kt b/controls-pi/src/main/kotlin/space/kscience/controls/pi/PiPlugin.kt
index e3d6a0a..547a142 100644
--- a/controls-pi/src/main/kotlin/space/kscience/controls/pi/PiPlugin.kt
+++ b/controls-pi/src/main/kotlin/space/kscience/controls/pi/PiPlugin.kt
@@ -1,5 +1,6 @@
 package space.kscience.controls.pi
 
+import space.kscience.controls.ports.Ports
 import space.kscience.dataforge.context.AbstractPlugin
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.PluginFactory
@@ -7,6 +8,8 @@ import space.kscience.dataforge.context.PluginTag
 import space.kscience.dataforge.meta.Meta
 
 public class PiPlugin : AbstractPlugin() {
+    public val ports: Ports by require(Ports)
+
     override val tag: PluginTag get() = Companion.tag
 
     public companion object : PluginFactory<PiPlugin> {