Expose trigger polarity to Micro-Manager in Point Grey device adapter

This change exposes the trigger polarity to Micro-Manager (if it exists). The polarity
determines whether an external trigger starts an exposure when it is "high" or "low".

Co-authored with @GiorgioTortarolo

DeviceAdapters/PointGrey/PointGrey.cpp

@@ -59,6 +59,9 @@ const char* g_InternalTrigger          = "Internal";
 const char* g_ExternalTrigger          = "External";
 const char* g_SoftwareTrigger          = "Software";
 const char* g_CameraTime               = "CameraTime";
+const char* g_PolarityLow              = "Low";
+const char* g_PolarityHigh             = "High";
+
 
 /////////////////////////////////////////////////////
 
@@ -190,6 +193,7 @@ PointGrey::PointGrey(const char* deviceName) :
    isCapturing_(false),
    f7InUse_(false),
    triggerMode_(TRIGGER_INTERNAL),
+   triggerPolarity_(TRIGGER_POLARITY_LOW),
    externalTriggerGrabTimeout_(60000),
    bytesPerPixel_(1),
    imgBuf_(0),
@@ -686,6 +690,14 @@ int PointGrey::Initialize()
       }
    }
 
+   if (triggerModeInfo.polaritySupported == true)
+   {
+       CPropertyAction* pAct = new CPropertyAction(this, &PointGrey::OnTriggerPolarity);
+       CreateProperty("TriggerPolarity", g_PolarityLow, MM::String, false, pAct, false);
+       AddAllowedValue("TriggerPolarity", g_PolarityLow);
+       AddAllowedValue("TriggerPolarity", g_PolarityHigh);
+   }
+
    // We most likely want little endian bit order
    ret = SetEndianess(true);
    if (ret != DEVICE_OK)
@@ -1823,6 +1835,65 @@ int PointGrey::OnTriggerMode(MM::PropertyBase* pProp, MM::ActionType eAct)
    return DEVICE_OK;
 }
 
+/***************************************************************
+* Handles Trigger Polarity
+*
+* This property determines whether an external trigger must be
+* in the high or low state to start an exposure..
+*/
+int PointGrey::OnTriggerPolarity(MM::PropertyBase* pProp, MM::ActionType eAct)
+{
+  if (eAct == MM::AfterSet)
+  {
+    Error error = cam_.StopCapture();
+    // if camera is not capturing, StopCapture will return an error.
+    // probably safe to ignore, it is bad to return
+    if (error != PGRERROR_OK && error != PGRERROR_ISOCH_NOT_STARTED)
+    {
+      SetErrorText(ALLERRORS, error.GetDescription());
+      return ALLERRORS;
+    }
+
+    std::string polarity;
+    pProp->Get(polarity);
+
+    int ret = DEVICE_OK;
+    unsigned short newPolarity;
+    if ( polarity == g_PolarityLow ) {
+      newPolarity = 0;
+      ret = SetTriggerPolarity(newPolarity);
+    }
+    else {
+      newPolarity = 1;
+      ret = SetTriggerPolarity(newPolarity);
+    }
+    if ( ret != DEVICE_OK )
+    {
+      return ret;
+    }
+    error = cam_.StartCapture();
+    if ( error != PGRERROR_OK )
+    {
+      SetErrorText(ALLERRORS, error.GetDescription());
+      return ALLERRORS;
+    }
+
+    triggerPolarity_ = newPolarity;
+  }
+  else if ( eAct == MM::BeforeGet )
+  {
+    if (triggerPolarity_ == TRIGGER_POLARITY_LOW)
+    {
+      pProp->Set(g_PolarityLow);
+    }
+    else {
+      pProp->Set(g_PolarityHigh);
+    }
+  }
+
+  return DEVICE_OK;
+}
+
 /***********************************************************************
 * Sets a register in the camera to indicate the endianness of the 
 * output.  It seems that MM wants little endian, most likely since 
@@ -2264,6 +2335,47 @@ int PointGrey::SetTriggerMode(const unsigned short newMode)
    return DEVICE_OK;
 }
 
+int PointGrey::SetTriggerPolarity(const unsigned short newPolarity)
+{
+    if ((newPolarity != 0) && (newPolarity != 1))
+    {
+      return ERR_INVALID_TRIGGER_POLARITY;
+    }
+
+    if (triggerPolarity_ != newPolarity)
+    {
+      // Get current trigger settings
+      TriggerMode triggerMode;
+      Error error = cam_.GetTriggerMode(&triggerMode);
+      if (error != PGRERROR_OK) {
+      }
+      else
+      {
+        triggerMode.polarity = newPolarity;
+        error = cam_.SetTriggerMode(&triggerMode);
+        if (error != PGRERROR_OK)
+        {
+            SetErrorText(ALLERRORS, error.GetDescription());
+            return ALLERRORS;
+        }
+
+        if (triggerMode.source == 7) // 7 for software trigger
+        {
+          // Poll to ensure camera is ready
+          int ret = PollForTriggerReady(2000);
+          if (ret != DEVICE_OK)
+          {
+              return ret;
+          }
+        }
+
+        triggerPolarity_ = newPolarity;
+      }
+    }
+
+    return DEVICE_OK;
+}
+
 int PointGrey::SetGrabTimeout(const unsigned long timeoutMs)
 {
    FC2Config config;

DeviceAdapters/PointGrey/PointGrey.h

@@ -35,12 +35,17 @@
 #define ERR_NOT_READY_FOR_SOFTWARE_TRIGGER      12301
 #define ERR_UNAVAILABLE_TRIGGER_MODE_REQUESTED  12302
 #define ERR_UNKNOWN_TRIGGER_MODE_STRING         12303
+#define ERR_INVALID_TRIGGER_POLARITY            12304
 
 // Trigger modes
 #define TRIGGER_INTERNAL   0
 #define TRIGGER_EXTERNAL   1
 #define TRIGGER_SOFTWARE   2
 
+// Trigger polarities
+#define TRIGGER_POLARITY_LOW 0
+#define TRIGGER_POLARITY_HIGH 1
+
 using namespace FlyCapture2;
 
 //////////////////////////////////////////////////////////////////////////////
@@ -112,6 +117,7 @@ class PointGrey : public CCameraBase<PointGrey>
    int OnPixelType(MM::PropertyBase* pProp, MM::ActionType eAct);
    int OnFormat7Mode(MM::PropertyBase* pProp, MM::ActionType eAct);
    int OnTriggerMode(MM::PropertyBase* pProp, MM::ActionType eAct);
+   int OnTriggerPolarity(MM::PropertyBase* pProp, MM::ActionType eAct);
 
 private:
    void updatePixelFormats(unsigned int pixelFormatBitField);
@@ -121,6 +127,7 @@ class PointGrey : public CCameraBase<PointGrey>
    int PollForTriggerReady(const unsigned long timeoutMs);
    bool FireSoftwareTrigger();
    int SetTriggerMode(const unsigned short newMode);
+   int SetTriggerPolarity(const unsigned short newPolarity);
    int SetGrabTimeout(const unsigned long timeoutMs);
    int PowerCameraOn(const unsigned int timeoutMs);
    int TriggerModeFromString(std::string mode, unsigned short& tMode);
@@ -148,6 +155,7 @@ class PointGrey : public CCameraBase<PointGrey>
    bool f7InUse_;
    double exposureTimeMs_;
    unsigned short triggerMode_;
+   unsigned short triggerPolarity_;
    unsigned short snapTriggerMode_;
    unsigned long externalTriggerGrabTimeout_;
    unsigned short bytesPerPixel_;