fix #7 initialization bug

Author: RobTillaart

README.md

@@ -13,7 +13,8 @@ Arduino Library for X9C10X series digital potentiometer.
 
 ## Description
 
-This experimental library provides a X9C10X base class and four derived classes for specific digital potentiometer.
+This experimental library provides a X9C10X base class and 
+four derived classes for specific digital potentiometer.
 
 | type   | resistance | tested  |  notes       |
 |:------:|:----------:|:-------:|:-------------|
@@ -68,8 +69,12 @@ Note: **begin()** has a hard coded 500uS delay so the device can wake up.
 Note: multiple devices can be controlled, just by giving them an unique selectPin.
 This behaviour is similar to the SPI select pin.
 
-- **void setPosition(uint8_t position, bool forced = false)** sets the wiper to a position between 0 and 99. The movement is relative to the current (cached) position.
-If forced is set to true, the cached position is ignored and the new position will be cached. 
+- **void setPosition(uint8_t position, bool forced = false)** sets the wiper 
+to a position between 0 and 99. 
+The movement is relative to the current (cached) position.
+If forced is set to true, the wiper will be moved to the closest end position and 
+from there moved to the requested position. 
+The cached position is ignored and the new position will be cached. 
 - **uint8_t getPosition()** returns the current position.
 - **bool incr()** moves one position up (if possible). 
 Returns true if moved and false if already at end position.
@@ -78,6 +83,9 @@ Returns true if moved and false if already at end position.
 - **uint32_t getOhm()** returns the position expressed in Ohm.
 The returned value does depend on the value passed in the constructor.
 - **uint32_t getMaxOhm()** returns the maximum value ( =  parameter from constructor). 
+- **uint32_t Ohm2Position(uint32_t value, bool invert = false)**
+Calculates (with rounding) the position nearest to the requested value. 
+If **invert == true** it uses the other wiper end as reference.
 
 
 #### Store 
@@ -87,6 +95,8 @@ Warning: use with care.
 - **uint8_t store()** stores the current position in the NVRAM of the device, 
 and returns the current position so it can later be used as position parameter for **begin()**. 
 
+Note: this function blocks for 20 milliseconds.
+
 If one uses an incorrect parameter position in **begin()** the internal state and the device 
 will probably be out of sync. One way to sync is call **begin()** with the right parameters. 
 The other way is to call **setPosition(0)** followed by **setPosition(99)** (or vice versa) 
@@ -156,10 +166,13 @@ Note: check datasheet for the range of the max voltage allowed.
 
 ## Future
 
+- update documentation
 - test different platforms
 - improve the hardcoded 500us delay in **begin()**
 - add error codes ?
-- test **store()**
+- add examples
+  - voltage divider
+- investigate and test **store()**
 - in the constructor rename **Ohm** parameter to value? 
   - The potentiometer can be used as a voltage divider (see above)
     so a better parameter name could be the anonymous **value**.

X9C10X.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: X9C10X.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.3
+// VERSION: 0.2.0
 // PURPOSE: Arduino Library for X9C10X series digital potentiometer.
 //     URL: https://github.com/RobTillaart/X9C10X
 //
@@ -12,7 +12,9 @@
 //                     rounding in getOhm(), documentation
 //  0.1.3  2022-02-22  add forced parameter to setPosition()
 //                     incr() and decr() return bool (made a step)
-//
+//  0.2.0  2022-07-09  fix #7 incorrect signal during initialize
+//                     update readme
+//                     add uint8_t Ohm2Position()
 
 
 #include "X9C10X.h"
@@ -30,6 +32,10 @@
 #define X9C10X_DOWN                 LOW
 
 
+/////////////////////////////////////////////////////////
+//
+//  PUBLIC
+//
 X9C10X::X9C10X(uint32_t maxOhm)
 {
   _maxOhm = maxOhm;
@@ -42,16 +48,19 @@ void X9C10X::begin(uint8_t pulsePin, uint8_t directionPin, uint8_t selectPin, ui
   _directionPin = directionPin;
   _selectPin    = selectPin;
 
+  //  #7 order of the initialization does matter
+  //     as it might introduce an unwanted STORE pulse.  
+  digitalWrite(_selectPin,    HIGH);
+  digitalWrite(_pulsePin,     HIGH);
+  digitalWrite(_directionPin, HIGH);
+
   pinMode(_pulsePin, OUTPUT);
   pinMode(_directionPin, OUTPUT);
   pinMode(_selectPin, OUTPUT);
 
-  digitalWrite(_pulsePin,     HIGH);
-  digitalWrite(_directionPin, HIGH);
-  digitalWrite(_selectPin,    HIGH);
-
   //  wiper power up time. Page 5.
-  delayMicroseconds(500);
+  //  slightly more efficient than delayMicros()
+  while (micros() < 500);
 
   //  reset defined position.
   _position = position;
@@ -123,9 +132,32 @@ uint8_t X9C10X::store()
 }
 
 
-////////////////////////////////////////////////////////////////////
+//  rounding needed!
+uint32_t X9C10X::getOhm()
+{
+  return (_maxOhm * _position + 49) / 99;
+};
+
+
+uint32_t X9C10X::getMaxOhm()
+{
+  return _maxOhm;
+};
+
+
+//  rounding needed!
+uint8_t X9C10X::Ohm2Position(uint32_t value, bool invert)
+{
+  if (value > _maxOhm) return 99;
+  uint8_t val = (99 * value + _maxOhm/2) / _maxOhm;
+  if (invert) return 99 - val;
+  return val;
+}
+
+
+/////////////////////////////////////////////////////////
 //
-//  PRIVATE
+//  PROTECTED
 //
 void X9C10X::_move(uint8_t direction, uint8_t steps)
 {

X9C10X.h

@@ -2,14 +2,14 @@
 //
 //    FILE: X9C10X.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.3
+// VERSION: 0.2.0
 // PURPOSE: Arduino Library for X9C10X series digital potentiometer.
 //     URL: https://github.com/RobTillaart/X9C10X
 
 
 #include "Arduino.h"
 
-#define X9C10X_LIB_VERSION        (F("0.1.3"))
+#define X9C10X_LIB_VERSION        (F("0.2.0"))
 
 
 class X9C10X
@@ -35,10 +35,10 @@ class X9C10X
   uint8_t  store();
 
   //  current resistance in ohm.
-  //  Q: rounding needed?
-  uint32_t getOhm() { return (_maxOhm * _position + 49) / 99; };
-  // misc
-  uint32_t getMaxOhm() { return _maxOhm; };
+  uint32_t getOhm();
+  uint32_t getMaxOhm();
+  uint8_t  Ohm2Position(uint32_t value, bool invert = false);
+
 
   //  Q: needed?
   uint16_t getType() { return _type; };

keywords.txt

@@ -17,6 +17,7 @@ decr	KEYWORD2
 
 getOhm	KEYWORD2
 getMaxOhm	KEYWORD2
+Ohm2Position	KEYWORD2
 
 store	KEYWORD2
 getType	KEYWORD2

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/X9C10X.git"
   },
-  "version": "0.1.3",
+  "version": "0.2.0",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=X9C10X
-version=0.1.3
+version=0.2.0
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino Library for X9C10X series digital potentiometer.