daisy_fx1200.rb in extface-0.4.9

- old
+ new

@@ -16,10 +16,11 @@
     
     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",
@@ -241,15 +242,25 @@
       end
       return result
     end
     
     def frecv(timeout) # return RespFrame or nil
-      if frame_bytes = pull(timeout)
-        return RespFrame.new(frame_bytes.b)
-      else
-        errors.add :base, "No data received from device"
-        return nil
+      rframe = nil
+      BAD_SEQ_MAX_COUNT.times do
+        if frame_bytes = pull(timeout)
+          rframe = RespFrame.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"
+            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
    
     private
       def build_sale_data(item)
         "".tap() do |data|
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