From 39765e002e71a2dd54e932469877acfc1b6fcb67 Mon Sep 17 00:00:00 2001
From: pux <pux@pux.dom>
Date: Thu, 7 Jan 2021 19:39:17 +0100
Subject: add *.exp; (this is redundant information, just to be able to diff
 later on)

---
 exp/FB_INC_DECODER.EXP | 133 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 exp/FB_INC_DECODER.EXP

(limited to 'exp/FB_INC_DECODER.EXP')

diff --git a/exp/FB_INC_DECODER.EXP b/exp/FB_INC_DECODER.EXP
new file mode 100644
index 0000000..2433c18
--- /dev/null
+++ b/exp/FB_INC_DECODER.EXP
@@ -0,0 +1,133 @@
+
+(* @NESTEDCOMMENTS := 'Yes' *)
+(* @PATH := '' *)
+(* @OBJECTFLAGS := '0, 8' *)
+(* @SYMFILEFLAGS := '2048' *)
+FUNCTION_BLOCK FB_INC_DECODER
+VAR_INPUT
+	IN_xChA			: BOOL;		(* Channel A *)
+	IN_xChB			: BOOL;		(* Channel B, 90-degree rotated to Channel A *)
+	IN_xReset		: BOOL;		(* Reset counter to 0 *)
+
+	IN_xEnPosWindow	: BOOL; 	(* TRUE if you want to overflow the counting at min/max values below *)
+	IN_diMinVal		: DINT;
+	IN_diMaxVal		: DINT;
+END_VAR
+VAR_OUTPUT
+	OUT_diActVal	: DINT;
+END_VAR
+VAR_OUTPUT PERSISTENT
+	OUT_pdiActVal	: DINT;
+END_VAR
+VAR
+	rtChA		: R_TRIG;
+	rtChB		: R_TRIG;
+	ftChA		: F_TRIG;
+	ftChB		: F_TRIG;
+	xFirstCycle	: BOOL;
+END_VAR
+
+(*
+
+Incremental Encoder Decoder FB
+Author: mo
+Date: 2019-02
+
+	alternative OSCAT implementation (faulty!) below:
+	
+	<OSCAT>
+	axb := cha XOR chb;
+	
+	(* create pulses for channel a *)
+	clka := cha XOR edgea;
+	edgea := cha;
+	
+	clkb := chb XOR edgeb;
+	edgeb := chb;
+	
+	(* create pulses for both channels *)
+	clk := clka OR clkb;
+	
+	(* set the direction output *)
+	IF axb AND clka THEN dir := TRUE; END_IF;
+	IF axb AND clkb THEN dir := FALSE; END_IF;
+	
+	(* increment or decrement the counter *)
+	IF clk AND dir THEN cnt := cnt + 1; END_IF;
+	IF clk AND NOT dir THEN cnt := cnt -1; END_IF;
+	
+	(* reset the counter if rst active *)
+	IF rst THEN cnt := 0; END_IF;
+	</OSCAT>
+
+=> problem here is: if your first pulse is e.g. a rising edge on CHb
+   with a high signal on CHa, it will increment cnt, but in the FALSE
+   direction instead of the TRUE direction. so your first pulse might count
+   into the wrong direction!
+
+
+This implementation accounts for all possible transitions.
+You can use OUT_diActVal or the persistent Version OUT_pdiActVal if your hardware
+is not moving while powered off to avoid reference runs at each restart of the PLC.
+
+  1  |----|    |----|    |-
+A 0 _|    |____|    |____|
+
+  1     |----|    |----|    |-
+B 0    _|    |____|    |____|
+
+*)
+
+(* @END_DECLARATION := '0' *)
+rtChA(clk:=IN_xChA);
+rtChB(clk:=IN_xChB);
+ftChA(clk:=IN_xChA);
+ftChB(clk:=IN_xChB);
+
+(* don't evaluate the changing edges when PLC starts up *)
+IF xFirstCycle THEN
+	IF 		(rtChA.Q AND NOT IN_xChB)
+		OR	(ftChA.Q AND IN_xChB)
+		OR	(rtChB.Q AND IN_xChA)
+		OR	(ftChB.Q AND NOT IN_xChA)
+	THEN
+		OUT_diActVal := OUT_diActVal + 1;
+		OUT_pdiActVal := OUT_pdiActVal + 1;
+	END_IF
+
+	IF		(rtChA.Q AND IN_xChB)
+		OR	(ftChA.Q AND NOT IN_xChB)
+		OR	(rtChB.Q AND NOT IN_xChA)
+		OR	(ftChB.Q AND IN_xChA)
+	THEN
+		OUT_diActVal := OUT_diActVal - 1;
+		OUT_pdiActVal := OUT_pdiActVal - 1;
+	END_IF
+END_IF
+
+IF IN_xReset THEN
+	OUT_diActVal := 0;
+	OUT_pdiActVal := 0;
+END_IF
+
+IF IN_xEnPosWindow THEN
+	IF OUT_diActVal < IN_diMinVal THEN
+		OUT_diActVal := IN_diMaxVal - 1;
+	END_IF
+
+	IF OUT_diActVal >= IN_diMaxVal THEN
+		OUT_diActVal := IN_diMinVal;
+	END_IF
+
+	(* for persistent counter *)
+	IF OUT_pdiActVal < IN_diMinVal THEN
+		OUT_pdiActVal := IN_diMaxVal - 1;
+	END_IF
+
+	IF OUT_pdiActVal >= IN_diMaxVal THEN
+		OUT_pdiActVal := IN_diMinVal;
+	END_IF
+END_IF
+
+xFirstCycle := TRUE;
+END_FUNCTION_BLOCK
-- 
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