0.2.0 74HC154

Author: RobTillaart

libraries/74HC154/74HC154.h

@@ -3,14 +3,14 @@
 //    FILE: 74HC154.h
 //  AUTHOR: Rob Tillaart
 //    DATE: 2024-02-22
-// VERSION: 0.1.0
+// VERSION: 0.2.0
 // PURPOSE: Arduino library for the 74HC154 4-to-16 line decoder/demultiplexer.
 //     URL: https://github.com/RobTillaart/74HC154
 
 
 #include "Arduino.h"
 
-#define LIB_74HC154_VERSION         (F("0.1.0"))
+#define LIB_74HC154_VERSION         (F("0.2.0"))
 
 
 
@@ -86,16 +86,19 @@ class DEV_74HC154
 
   void enable()
   {
+    //  if (_enable == 255) return;
     digitalWrite(_enable, LOW);
   }
 
   void disable()
   {
+    //  if (_enable == 255) return;
     digitalWrite(_enable, HIGH);
   }
 
   bool isEnabled()
   {
+    //  if (_enable == 255) return false???;
     return digitalRead(_enable);
   }
 
@@ -107,13 +110,14 @@ class DEV_74HC154
 
   void _setLine()
   {
-    digitalWrite(_pin[0], _line & 0x01);
-    digitalWrite(_pin[1], _line & 0x02);
-    digitalWrite(_pin[2], _line & 0x04);
-    digitalWrite(_pin[3], _line & 0x08);
+    digitalWrite(_pin[0], (_line >> 0) & 0x01);
+    digitalWrite(_pin[1], (_line >> 1) & 0x01);
+    digitalWrite(_pin[2], (_line >> 2) & 0x01);
+    digitalWrite(_pin[3], (_line >> 3) & 0x01);
   }
 
 /*
+  //  read from the pins instead of from cache
   uint8_t getLine()
   {
     uint8_t value = digitalRead(_pin[0]);

libraries/74HC154/CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.2.0] - 2025-06-03
+- fix #2, support for ATtiny402 (kudos to trent-lane)
+- update readme.md
+- minor edits
+
+----
+
 ## [0.1.0] - 2024-02-23
 - initial version
 

libraries/74HC154/LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2024-2024 Rob Tillaart
+Copyright (c) 2024-2025 Rob Tillaart
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

libraries/74HC154/README.md

@@ -16,11 +16,37 @@ Arduino library for the 74HC154 4-to-16 line decoder/demultiplexer.
 
 ## Description
 
-This library controls the 74HC154 4 to 6 line decoder. 
-With 4 IO lines one can select one of 16 output lines. 
+This library controls the 74HC154 4 to 16 line decoder.
+With 4 IO lines one can select one of 16 output lines to go LOW.
+The other lines are HIGH.
 
+The 74HC154 device has two input enable lines E0 and E1.
+If one or both enable lines are HIGH all outputs are HIGH and there
+is no line LOW.
+If both enable lines are LOW, there is one line LOW (defined by the
+address pins) and all others are HIGH.
 
-#### Related
+The library supports only one ENABLE pin which is sufficient to control
+the device. Set the other pin permanent LOW if not needed, however
+never let the enable line(s) float.
+
+One can use one of the enable inputs as the multiplexed data input.
+Keep the other enable input LOW and the addressed output will follow
+the state of the applied data.
+
+
+### SetLine
+
+When changing a line, not all address lines are set simultaneously as
+individual digitalWrite()'s are used.
+This might cause other lines be selected for a few microseconds which
+might affect the working of your project.
+To prevent this behaviour one can **disable()** the device before
+**setLine()** and **enable()** the device afterwards.
+This only works if the enablePin is set in the constructor.
+
+
+### Related
 
 - https://github.com/RobTillaart/74HC138  (3 to 8 selector)
 - https://github.com/RobTillaart/74HC154  (4 to 16 selector)
@@ -36,26 +62,26 @@ With 4 IO lines one can select one of 16 output lines.
 #include "74HC154.h"
 ```
 
-#### Constructor
+### Constructor
 
-- **74HC154(uint8_t pin0, uint8_t pin1, uint8_t pin2, uint8_t pin3, uint8_t pinEnable = 255)** 
+- **74HC154(uint8_t pin0, uint8_t pin1, uint8_t pin2, uint8_t pin3, uint8_t pinEnable = 255)**
 set the 4 selection IO lines from pin numbers.
 Optionally set the enable pin, connect to E1 or E2, see datasheet.
-- **74HC154(uint8_t \* pins, uint8_t pinEnable = 255)** 
+- **74HC154(uint8_t \* pins, uint8_t pinEnable = 255)**
 set the 4 selection IO lines from an array.
 The pins array should have at least 4 elements.
 Optionally set the enable pin, connect to E1, see datasheet.
 
 
-#### Select line
+### Select line
 
 - **bool setLine(uint8_t line)** set line 0 .. 15. Returns false if out of range.
-- **uint8_t getLine()** returns 0 .. 15
+- **uint8_t getLine()** returns 0 .. 15, default line selected = 0.
 - **void nextLine()** selects the next line, wraps back to 0 if needed.
 - **void prevLine()** selects the previous line, wraps to 15 if needed.
 
 
-#### Enable
+### Enable
 
 Works only if enable line is set in constructor.
 
@@ -76,9 +102,29 @@ Works only if enable line is set in constructor.
 
 #### Could
 
+- AVR optimize digitalWrite() as pins are known.
+- investigate performance gain setLine by using a changed mask.
+  - will decrease if all 4 lines change
+
+```cpp
+  void _setLine()
+  {
+    uint8_t changed = _oldLine ^ _line;
+    for (int i = 0; i < 4; i++)
+    {
+      if (changed & 0x01) digitalWrite(_pin[i], (_line >> i) & 0x01);
+      changed >>= 1;
+    }
+  }
+```
+
+- let next/prevLine() return the new line selected?
+- optimize the enable functions by checking pin nr.?
+
 
 #### Wont
 
+- set default line in constructor?
 
 ## Support
 

libraries/74HC154/library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/74HC154.git"
   },
-  "version": "0.1.0",
+  "version": "0.2.0",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",

libraries/74HC154/library.properties

@@ -1,5 +1,5 @@
 name=74HC154
-version=0.1.0
+version=0.2.0
 author=Rob Tillaart <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=Arduino library for the 74HC154 4 to 16 line decoder/demultiplexer.