Read back configured DAC value when queried via OPC/UA.

Author: aentinger

examples/opcua_server/opcua_server.ino

@@ -334,9 +334,13 @@ void setup()
             exp_analog->add_analog_output(
               opc_ua_server,
               analog_out_name,
+              [i, a]()
+              {
+                return reinterpret_cast<AnalogExpansion *>(OptaController.getExpansionPtr(i))->pinVoltage(a);
+              },
               [i, a](float const voltage)
               {
-                return reinterpret_cast<AnalogExpansion *>(OptaController.getExpansionPtr(i))->pinVoltage(a, voltage);
+                reinterpret_cast<AnalogExpansion *>(OptaController.getExpansionPtr(i))->pinVoltage(a, voltage);
               });
             output_num++;
           }

src/expansion/AnalogExpansion.cpp

@@ -81,9 +81,10 @@ void
 AnalogExpansion::add_analog_output(
   UA_Server * server,
   const char * display_name,
+  AnalogOutput::OnReadRequestFunc const on_read_request,
   AnalogOutput::OnWriteRequestFunc const on_write_request_func)
 {
-  _analog_output_mgr->add_analog_output(server, display_name, on_write_request_func);
+  _analog_output_mgr->add_analog_output(server, display_name, on_read_request, on_write_request_func);
 }
 
 void

src/expansion/AnalogExpansion.h

@@ -64,6 +64,7 @@ class AnalogExpansion : public Expansion
   add_analog_output(
     UA_Server * server,
     const char * display_name,
+    AnalogOutput::OnReadRequestFunc const on_read_request,
     AnalogOutput::OnWriteRequestFunc const on_write_request_func);
 
   void

src/io/analog/AnalogOutput.cpp

@@ -24,6 +24,20 @@ namespace opcua
  * FUNCTION DEFINITION
  **************************************************************************************/
 
+static void
+analog_input_on_read_request(
+  UA_Server *server,
+  const UA_NodeId *sessionId,
+  void *sessionContext,
+  const UA_NodeId *nodeid,
+  void *nodeContext,
+  const UA_NumericRange *range,
+  const UA_DataValue *data)
+{
+  AnalogOutput * this_ptr = reinterpret_cast<AnalogOutput *>(nodeContext);
+  this_ptr->onReadRequest(server, nodeid);
+}
+
 static void
 analog_output_on_write_request(
   UA_Server *server,
@@ -45,8 +59,10 @@ analog_output_on_write_request(
 
 AnalogOutput::AnalogOutput(
   UA_NodeId const & node_id,
+  OnReadRequestFunc const on_read_request,
   OnWriteRequestFunc const on_write_request)
 : _node_id{node_id}
+, _on_read_request{on_read_request}
 , _on_write_request{on_write_request}
 {
 
@@ -61,13 +77,14 @@ AnalogOutput::create(
   UA_Server * server,
   UA_NodeId const & parent_node_id,
   const char * display_name,
+  OnReadRequestFunc const on_read_request,
   OnWriteRequestFunc const on_write_request)
 {
   UA_StatusCode rc = UA_STATUSCODE_GOOD;
 
   UA_VariableAttributes analog_output_value_attr = UA_VariableAttributes_default;
 
-  UA_Float analog_output_value = 0.;
+  UA_Float analog_output_value = on_read_request();
   UA_Variant_setScalar(&analog_output_value_attr.value, &analog_output_value, &UA_TYPES[UA_TYPES_FLOAT]);
 
   analog_output_value_attr.displayName = UA_LOCALIZEDTEXT("en-US", (char *)display_name);
@@ -95,7 +112,7 @@ AnalogOutput::create(
   }
 
   /* Create an instance of AnalogOutput here. */
-  auto const instance_ptr = std::make_shared<AnalogOutput>(node_id, on_write_request);
+  auto const instance_ptr = std::make_shared<AnalogOutput>(node_id, on_read_request, on_write_request);
 
   rc = UA_Server_setNodeContext(server, node_id, reinterpret_cast<void *>(instance_ptr.get()));
   if (UA_StatusCode_isBad(rc))
@@ -106,7 +123,7 @@ AnalogOutput::create(
   }
 
   UA_ValueCallback callback;
-  callback.onRead = NULL;
+  callback.onRead = analog_input_on_read_request;
   callback.onWrite = analog_output_on_write_request;
   rc = UA_Server_setVariableNode_valueCallback(server, node_id, callback);
   if (UA_StatusCode_isBad(rc))
@@ -119,6 +136,23 @@ AnalogOutput::create(
   return instance_ptr;
 }
 
+void
+AnalogOutput::onReadRequest(
+  UA_Server * server,
+  UA_NodeId const * node_id)
+{
+  /* Obtain the value of the analog input pin. */
+  float const in_x_val = _on_read_request();
+  /* Update the variable node. */
+  UA_Float in_x_val_opcua_value = in_x_val;
+  UA_Variant in_x_val_opcua_variant;
+  UA_Variant_init(&in_x_val_opcua_variant);
+  UA_Variant_setScalar(&in_x_val_opcua_variant, &in_x_val_opcua_value, &UA_TYPES[UA_TYPES_FLOAT]);
+  UA_Server_writeValue(server, *node_id, in_x_val_opcua_variant);
+  /* Some debug output. */
+  UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "%s: value = %f", __PRETTY_FUNCTION__, in_x_val);
+}
+
 void
 AnalogOutput::onWriteRequest(
   UA_Server * server,

src/io/analog/AnalogOutput.h

@@ -35,6 +35,7 @@ class AnalogOutput
 {
 public:
   typedef std::shared_ptr<AnalogOutput> SharedPtr;
+  typedef std::function<float(void)> OnReadRequestFunc;
   typedef std::function<void(float)> OnWriteRequestFunc;
 
 
@@ -43,23 +44,32 @@ class AnalogOutput
     UA_Server * server,
     UA_NodeId const & parent_node_id,
     const char * display_name,
+    OnReadRequestFunc const on_read_request,
     OnWriteRequestFunc const on_write_request);
 
 
   AnalogOutput(
     UA_NodeId const & node_id,
+    OnReadRequestFunc const on_read_request,
     OnWriteRequestFunc const on_write_request);
 
 
-  void onWriteRequest(
+  void
+  onReadRequest(
+    UA_Server * server,
+    UA_NodeId const * node_id);
+
+  void
+  onWriteRequest(
     UA_Server * server,
     UA_NodeId const * node_id,
     float const voltage);
 
 
 private:
   UA_NodeId _node_id;
-  OnWriteRequestFunc _on_write_request;
+  OnReadRequestFunc const _on_read_request;
+  OnWriteRequestFunc const _on_write_request;
 };
 
 /**************************************************************************************

src/io/analog/AnalogOutputManager.cpp

@@ -73,9 +73,10 @@ void
 AnalogOutputManager::add_analog_output(
   UA_Server * server,
   const char * display_name,
+  AnalogOutput::OnReadRequestFunc const on_read_request,
   AnalogOutput::OnWriteRequestFunc const on_write_request_func)
 {
-  auto const analog_output = AnalogOutput::create(server, _node_id, display_name, on_write_request_func);
+  auto const analog_output = AnalogOutput::create(server, _node_id, display_name, on_read_request, on_write_request_func);
   if (!analog_output) {
     UA_LOG_ERROR(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "%s: AnalogOutput::create(...) failed: returned nullptr", __PRETTY_FUNCTION__);
     return;

src/io/analog/AnalogOutputManager.h

@@ -51,6 +51,7 @@ class AnalogOutputManager
   add_analog_output(
     UA_Server * server,
     const char * display_name,
+    AnalogOutput::OnReadRequestFunc const on_read_request,
     AnalogOutput::OnWriteRequestFunc const on_write_request_func);