ersatzwerte

1 files changed, 51 insertions, 30 deletions

diff --git a/ebus-racket/ebus/layer7.rkt b/ebus-racket/ebus/layer7.rkt
index b3caf0b..b43a58a 100644
--- a/ebus-racket/ebus/layer7.rkt
+++ b/ebus-racket/ebus/layer7.rkt
@@ -8,6 +8,11 @@
 
 (define-logger ebus7)
 
+(define (ersatzwert)
+  'ersatzwert)
+(define (ersatzwert? v)
+  (eq? (ersatzwert) v))
+
 (define definition
  (let* ([in (open-input-file "../ebus-xml/ebus.xml")]
 		[xexpr (parameterize ([collapse-whitespace #t]
@@ -94,19 +99,25 @@
 
 ;; type data1b
 (define (field-decoder-data1b value)
-  value)
+  (if (= value #x80)
+	(ersatzwert)
+	value))
 
 ;; type data1c
 (define (field-decoder-data1c value)
-  (/ value 2.0))
+  (if (= value #xff)
+	(ersatzwert)
+	(/ value 2.0)))
 
 ;; type data2b
 (define (field-decoder-data2b lowByte highByte)
-  (if (= (bitwise-and highByte 128) 128)
-      (* -1 
-	 (+ (+ 256 (bitwise-not highByte))
-	    (/ (+ 256 (bitwise-not (+ lowByte 1))) 256.0)))
-      (+ highByte (/ lowByte 256.0))))
+  (if (and (= highByte 128)  (= lowByte 0))
+	(ersatzwert)
+	(if (= (bitwise-and highByte 128) 128)
+	   (* -1 
+		  (+ (+ 256 (bitwise-not highByte))
+			 (/ (+ 256 (bitwise-not (+ lowByte 1))) 256.0)))
+	   (+ highByte (/ lowByte 256.0)))))
 
  ;; type data2c
  ;;    Beispiel für die Berechnung:
@@ -118,22 +129,25 @@
  ;;    + dez(Low_ Nibble (Low Byte (x))) / 16
 (define (field-decoder-data2c lowByte highByte)
   (define (lowNibble v)
-    (bitwise-and v #x0f))
+	(bitwise-and v #x0f))
   (define (highNibble v)
-    (arithmetic-shift v -4))
+	(arithmetic-shift v -4))
   (define (u-not v)
-    (+ 256 (bitwise-not v)))
-  (if (= (bitwise-and highByte 128) 128)
-      (* -1
-	  (+ (arithmetic-shift (u-not highByte) 4)
-	     (highNibble (u-not lowByte))
-             (/ (+ (lowNibble (u-not lowByte)) 1)
-                16.0)))
-      (+ (arithmetic-shift highByte 4)
-         (highNibble lowByte)
-         (/
-           (lowNibble lowByte)
-           16))))
+	(+ 256 (bitwise-not v)))
+
+  (if (and (= highByte 128)  (= lowByte 0))
+	(ersatzwert)
+	(if (= (bitwise-and highByte 128) 128)
+	   (* -1
+		  (+ (arithmetic-shift (u-not highByte) 4)
+			 (highNibble (u-not lowByte))
+			 (/ (+ (lowNibble (u-not lowByte)) 1)
+				16.0)))
+	   (+ (arithmetic-shift highByte 4)
+		  (highNibble lowByte)
+		  (/
+			(lowNibble lowByte)
+			16)))))
 
 ;; type byteEnum
 (define (field-decoder-byteEnum value field-definition)
@@ -149,13 +163,18 @@
 
 ;; type word
 (define (field-decoder-word lowByte highByte)
-  (+ lowByte
-     (arithmetic-shift highByte 8)))
+  (define value
+	(+ lowByte (arithmetic-shift highByte 8)))
+  (if (= value #xffff)
+	(ersatzwert)
+	value))
 
 ;; type bcd
 (define (field-decoder-bcd value)
-  (+ (bitwise-and value #x0f)
-     (arithmetic-shift value -4)))
+  (if (= value #xff)
+	(ersatzwert)
+	(+ (bitwise-and value #x0f)
+	   (arithmetic-shift value -4))))
   
 ;; read one ebus-paket or eof from input-port
 ;; or return #<eof>
@@ -165,10 +184,12 @@
 	 (paket-parse paket))
 	(else paket)))
 
-(provide (prefix-out layer7- paket)
-         (prefix-out layer7- paket-parse)
-         (prefix-out layer7- device)
-         (prefix-out layer7- device-name)
-         (prefix-out layer7- definition)
+(provide (prefix-out layer7- ersatzwert)
+		 (prefix-out layer7- ersatzwert?)
+		 (prefix-out layer7- paket)
+		 (prefix-out layer7- paket-parse)
+		 (prefix-out layer7- device)
+		 (prefix-out layer7- device-name)
+		 (prefix-out layer7- definition)
 		 ;; read ebus from port an return fields from next paket
 		 (prefix-out layer7- read-ebus))