catch the case when sensirion is not working

- add use_pressure to nv control for selecting whether nv control
  is using the flow from the sensirion sensor or the pump pressure
- this is triggered when sensirion is reading 0 (incl. stddev)

tcl/drivers/nvstep.tcl

@@ -1,7 +1,7 @@
 namespace eval nvstep {
 }
 
-proc stdConfig::nvstep {} {
+proc stdConfig::nvstep {args} {
   variable name
 
   controller syncedprot
@@ -9,7 +9,7 @@ proc stdConfig::nvstep {} {
 
   obj NvStep wr
   prop write nvstep::write
-  prop read "nvstep::read [silent 0 result instconfig sensirion]"
+  prop read nvstep::read
   prop enum fixed=0,controlled=1,automatic=2,close=3,open=4
   prop write nvstep::write
   prop lastpulse 0
@@ -22,6 +22,13 @@ proc stdConfig::nvstep {} {
   prop maxflow 0
   default 0
 
+  set sensirion 0
+  foreach arg $args {
+    if {$arg eq "1"} {
+      set sensirion 1
+    }
+  }
+
   kids "needle value" {
     node flow upd
 
@@ -39,6 +46,10 @@ proc stdConfig::nvstep {} {
     node flowp upd
     prop help "flow calculated from pressure before pump"
 
+    node use_pressure par -int [expr !$sensirion]
+    prop enum 1
+    prop help "use pressure instead of flow meter for control"
+
     node ctrl -none
     kids "control parameters" {
       node prop par 10
@@ -172,7 +183,11 @@ proc nvstep::poll {} {
           hupdate [sct]/status $umsg
         }
       }
-      set ist [hvali [sct]/flow]
+      if {[hval [sct]/use_pressure]} {
+        set ist [hvali [sct]/flowp]
+      } else {
+        set ist [hvali [sct]/flow]
+      }
       set tol [hvali [sct]/ctrl/tol]
       set a [sct amplitude]
       set t [sct t_after_delay]
@@ -270,29 +285,26 @@ proc nvstep::poll {} {
   return idle
 }
 
-proc nvstep::read {{sensirion 0}} {
+proc nvstep::read {} {
   hsetprop /cc/fa nvpath [sct]
   _cc updatescript /cc/fa nvstep::updatemode
   hsetprop /cc/f nvpath [sct]
-  if {$sensirion} {
-    hsetprop /nvflow flowsource flowmeter
+  hsetprop /cc/f nvctrl [sct controller]
+  hsetprop /cc/f flowsource pressure
+  _cc updatescript /cc/f nvstep::updateflow
+  catch {
+    hsetprop /nvflow flowsource flow
     hsetprop /nvflow nvpath [sct]
     hsetprop /nvflow nvctrl [sct controller]
     _hemot updatescript /nvflow nvstep::updateflow
-    hsetprop /cc/f flowsource pressref
-  } else {
-    hsetprop /cc/f nvctrl [sct controller]
-    hsetprop /cc/f flowsource flowpress
   }
-  _cc updatescript /cc/f nvstep::updateflow
   return unpoll
 }
 
 proc nvstep::updateflow {value} {
   # flowsource:
-  #    pressref: just update nv/flowp
-  #    flowmeter: update nv/flow
-  #    flowpress: flow from pressure
+  #   pressure: this is a pressure
+  #   flow: this is a flow from a flowmeter
 
   set source [silent pressure sct flowsource]
   set filter [lrange "[silent $value sct filter] $value" end-9 10]
@@ -317,21 +329,27 @@ proc nvstep::updateflow {value} {
     }
   }
   sct filtered $flow
-  if {$source eq "flowmeter"} {
+  if {$source eq "flow"} {
+    if {$flow < 1} {
+      # avoid negative flow values, but it smooth]
+      set flow [expr exp($flow - 1)]
+    }
     updateval [sct nvpath]/flow $flow
-  } else {
+  } elseif {$source eq "pressure" {
     if {$flow < -50} {
       set flow -62.5
     } else {
       set off [hval [sct nvpath]/calib/mbar_offset]
       set fpm [hval [sct nvpath]/calib/ln_per_min_per_mbar]
       set flow [expr ($flow - $off) * $fpm]
+      if {$flow < 1} {
+        # avoid negative flow values, but keep it smooth]
+        set flow [expr exp($flow - 1)]
+      }
     }
-    if {$source eq "pressref"} {
-      hupdate [sct nvpath]/flowp $flow
-      return 
-    }
-    updateval_e [sct nvpath]/flow $flow -62.5 no_sensor
+    updateval_e [sct nvpath]/flowp $flow -62.5 no_sensor
+  } else {
+    error "[sct] illegal flowsource: $source"
   }
   [sct nvctrl] queue [sct nvpath] read nvstep::poll
 }