fp550.rb in extface-0.4.9

- old
+ new

@@ -4,10 +4,11 @@
     
     RESPONSE_TIMEOUT = 3  #seconds
     INVALID_FRAME_RETRIES = 6  #count (bad length, bad checksum)
     ACKS_MAX_WAIT = 60 #count / nothing is forever
     NAKS_MAX_COUNT = 3 #count
+    BAD_SEQ_MAX_COUNT = 3
     
     TAX_GROUPS_MAP = {
       1 => "\xc0",
       2 => "\xc1",
       3 => "\xc2",
@@ -204,17 +205,28 @@
         errors.add :base, "#{ACKS_MAX_WAIT} ACKs Received. Abort!"
       end
       return result
     end
     
-    def frecv(timeout) # return RespFrame or nil
-      if frame_bytes = pull(timeout)
-        return Frame.new(frame_bytes.b)
-      else
-        errors.add :base, "No data received from device"
-        return nil
+    def frecv(timeout) # return Frame or nil
+      rframe = nil
+      BAD_SEQ_MAX_COUNT.times do
+        if frame_bytes = pull(timeout)
+          rframe = Frame.new(frame_bytes.b)
+          if rframe.seq.ord == sequence_number(false) #accept only current sequence number as reply
+            break
+          else
+            errors.add :base, "Sequence mismatch"
+            p "Invalid sequence (expected: #{sequence_number(false).to_s(16)}, got: #{rframe.seq.ord.to_s(16)})"
+            rframe = nil #invalidate mismatch sequence frame for the last retry
+          end
+        else
+          errors.add :base, "No data received from device"
+          break
+        end
       end
+      return rframe
     end
     
     def build_packet(cmd, data = "")
       "".b.tap() do |packet|
         packet << STX                     #Preamble. 1 byte long. Value: 01H.
@@ -257,12 +269,12 @@
           data << ",#{item.percent}" unless item.percent.blank?
           data << ",;#{'%.2f' % item.neto}" unless item.neto.blank?
         end
       end
       
-      def sequence_number
+      def sequence_number(increment = true)
         @seq ||= 0x1f
-        @seq += 1
+        @seq += 1 if increment
         @seq = 0x1f if @seq == 0x7f
         @seq
       end
       
       class Frame
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