0.5.2 AD524X

Author: RobTillaart

libraries/AD524X/AD524X.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: AD524X.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.5.1
+// VERSION: 0.5.2
 // PURPOSE: I2C digital potentiometer AD5241 AD5242
 //    DATE: 2013-10-12
 //     URL: https://github.com/RobTillaart/AD524X

libraries/AD524X/AD524X.h

@@ -2,7 +2,7 @@
 //
 //    FILE: AD524X.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.5.1
+// VERSION: 0.5.2
 // PURPOSE: I2C digital PotentioMeter AD5241 AD5242
 //    DATE: 2013-10-12
 //     URL: https://github.com/RobTillaart/AD524X
@@ -12,7 +12,7 @@
 #include "Wire.h"
 
 
-#define AD524X_LIB_VERSION    (F("0.5.1"))
+#define AD524X_LIB_VERSION    (F("0.5.2"))
 
 
 #define AD524X_OK             0

libraries/AD524X/CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.5.2] - 2025-06-20
+- fix #30, typo in keywords.txt
+- add example cascading_potmeters.ino
+- add CascadingPotmeters.md
+- minor edits
+
 ## [0.5.1] - 2024-03-16
 - add **getAddress()** (e.g. debugging)
 - improved **AD5241::write(rdac, ...)**
@@ -14,7 +20,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - update keywords.txt
 - minor edits examples
 
-
 ## [0.5.0] - 2023-11-29
 - remove ESP32 specific **begin()**
 - add (experimental) support or AD5280 / AD5282.

libraries/AD524X/Cascading Potmeters.md

@@ -0,0 +1,116 @@
+
+## Cascading Potentiometers
+
+Some notes on cascading potentiometers to have a large range with higher precision.
+
+Based upon - https://github.com/RobTillaart/AD524X/issues/26
+
+
+
+### Cascaded voltage divider
+
+Basic cascade to vary voltage connects:
+
+- all B's to GND
+- A of top level to 5V (or 3V3 whatever)
+- wiper W  of one level to the A of next leve;
+- last wiper W is final output
+
+
+```
+  5V ----A[  1000 K  ]B-----  GND
+              W
+              |
+    +---------+  V1
+    |
+    +----A[   100 K  ]B-----  GND
+              W
+              |
+    +---------+  V2
+    |
+    +----A[   10 K   ]B-----  GND
+              W
+              |
+              |
+              o  256 steps between GND and V2
+
+```
+
+Some math for a two potentiometer system see **cascading_voltage_divider.ino** example.
+
+
+### Range voltage divider
+
+The following setup has two potmeters, left and right, to define a range.
+- X can be set between 0.0 and 5.0 Volt and 
+- Y can be set between 0.0 and 5.0 volt.
+
+The third range potentiometer has 256 positions within the defined range range.
+E.g if left is set to 2.3 Volt and right is set to 2.5 Volt, 
+the range potentiometer divides this 0.2 volt in 256 steps of about a single millivolt (in theory).
+
+
+```
+         left limit pot           right limit pot
+
+  GND ----A[  100K  ]B----  5V  ----A[  100K  ]B---- GND
+               W                         W
+               |                         |
+               |        range pot        |
+               |                         |
+             X +------A[  100 K  ]B------+ Y
+                           W
+                           |
+                           |
+                           o   voltage between (0..Vcc)
+
+```
+
+
+### Cascaded resistor
+
+No dangling connectors give less noise as even a bad wiper will not break 
+the resistance chain completely. (Preferred imho)
+
+
+```
+     ----A[  1000K  ]B----+----A[  100 K  ]B----+----A[  10 K  ]B----+---o
+               W          |         W           |         W          |
+               |          |         |           |         |          |
+               +----------+         +-----------+         +----------+
+```
+
+
+Connected the AD524X as rheostats, saves a few connnections.
+
+```
+     ----A[  1000K  ]B    +----A[  100 K  ]B    +----A[  10 K  ]B    +---o
+               W          |         W           |         W          |
+               |          |         |           |         |          |
+               +----------+         +-----------+         +----------+
+```
+
+Some math for a two potentiometer system see **cascading_potentiometers.ino** example.
+
+
+### Zero switch
+
+An additional option is to connect the first A with the last B with "zero" switch to get 0 Ohm.
+This would solve the Wiper Resistance which is 60- 120 Ohm for the AD5422 (datasheet P3).
+Note with three wipers in a cascade the Wiper Resistance adds up to 200-360 Ohm,
+Optionally you can place a zero switch over every potentiometer.
+Drawback is extra components, control lines and code.
+
+```
+                            "zero" switch
+      +--------------------------o \o--------------------------------+
+      |                                                              |
+      |                                                              |
+     -+--A[  1000K  ]B    +----A[  100 K  ]B    +----A[  10 K  ]B    +---o
+               W          |         W           |         W          |
+               |          |         |           |         |          |
+               +----------+         +-----------+         +----------+
+```
+
+### 
+

libraries/AD524X/LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2013-2024 Rob Tillaart
+Copyright (c) 2013-2025 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/AD524X/README.md

@@ -43,13 +43,13 @@ The library defines AD524X_MIDPOINT == 127.
 To be used to set to defined mid-point.
 
 
-#### 0.5.0 Breaking change
+### 0.5.0 Breaking change
 
 The ESP32 specific **begin(sda, scl)** is removed.
 The user has to call **Wire.begin()** or equivalent himself before calling **begin()**.
 
 
-#### Related
+### Related
 
 - https://github.com/RobTillaart/AD520x
 - https://github.com/RobTillaart/AD524X
@@ -60,7 +60,7 @@ The user has to call **Wire.begin()** or equivalent himself before calling **beg
 - https://github.com/RobTillaart/X9C10X
 
 
-#### Compatibles ?
+### Compatibles ?
 
 If you find compatible devices please let me know.
 
@@ -77,6 +77,24 @@ The AD524X has two address lines to configure the I2C address. 0x2C - 0x2F
 |  47      |  0x2F     |  +5V  |  +5V  |
 
 
+### I2C multiplexing
+
+Sometimes you need to control more devices than possible with the default
+address range the device provides.
+This is possible with an I2C multiplexer e.g. TCA9548 which creates up
+to eight channels (think of it as I2C subnets) which can use the complete
+address range of the device.
+
+Drawback of using a multiplexer is that it takes more administration in
+your code e.g. which device is on which channel.
+This will slow down the access, which must be taken into account when
+deciding which devices are on which channel.
+Also note that switching between channels will slow down other devices
+too if they are behind the multiplexer.
+
+- https://github.com/RobTillaart/TCA9548
+
+
 ## Interface
 
 ```cpp
@@ -87,7 +105,7 @@ The library has a number of functions which are all quite straightforward.
 One can get / set the value of (both) the potentiometer(s), and the O1 and O2 output lines.
 
 
-#### Constructors
+### Constructors
 
 - **AD524X(uint8_t address, TwoWire \*wire = &Wire)** constructor base class,
 creates an instance with 2 potentiometer.
@@ -99,15 +117,15 @@ The developer is responsible for handling this correctly.
 - **AD5282(uint8_t address, TwoWire \*wire = &Wire)** create an instance with 2 potentiometer.
 
 
-#### Wire initialization
+### Initialization
 
 - **bool begin()** initialization of the object. 
 Note the user must call **wire.begin()** or equivalent before calling **begin()**.
 - **bool isConnected()** See if the address set in constructor is on the I2C bus.
 - **uint8_t getAddress()** returns address set in constructor, convenience.
 
 
-#### Basic IO
+### Basic IO
 
 - **uint8_t write(uint8_t rdac, uint8_t value)** set channel rdac 0/1 to value 0..255.
 - **uint8_t write(uint8_t rdac, uint8_t value, uint8_t O1, uint8_t O2)** idem + set output lines O1 and O2 too.
@@ -118,15 +136,15 @@ Note the user must call **wire.begin()** or equivalent before calling **begin()*
 - **uint8_t getO2()** read back O2 line.
 
 
-#### Misc
+### Misc
 
 - **uint8_t zeroAll()** sets potentiometer's to 0 and I/O to LOW.
 - **uint8_t reset()** sets potentiometer's to midpoint == 127 and I/O to LOW. (startup default)
 - **uint8_t midScaleReset(uint8_t rdac)** resets one potentiometer to midpoint == 127.
 - **uint8_t readBackRegister()** read register back, for debugging.
 
 
-#### Experimental
+### Experimental
 
 - **uint8_t shutDown()** check datasheet, not tested yet, use at own risk.
 

libraries/AD524X/examples/cascading_potentiometers/cascading_potentiometers.ino

@@ -0,0 +1,91 @@
+//    FILE: cascading_potentiometers.ino
+//  AUTHOR: Rob Tillaart
+//    DATE: 2024-11-05
+// PURPOSE: demo, calculates values for two cascaded potentiometers
+//     URL: https://github.com/RobTillaart/AD524X/issues/26
+//
+//  experimental
+//  precision is as good as the smallest potentiometer.
+//  math needs actual LSB and include Rwiper (TODO).
+//
+
+#include "Arduino.h"
+
+
+uint32_t start, stop;
+
+float LSB_A = 1e6 / 255.0;  //  1 M Ohm
+float LSB_B = 1e4 / 255.0;  //  10 K Ohm
+float R = 0;
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+  Serial.println(__FILE__);
+
+  //  find settings for all R's in steps of pot LSB_B
+  //  LSB_B iso 40 would be more exact but gives "no nice numbers"
+  for (uint32_t r = 0; r <= 1000000; r += 40)
+  {
+    search(r);
+  }
+
+}
+
+
+void loop()
+{
+}
+
+
+//
+//  searches optimal positions for pot A and pot B
+//  simplified math, ignores Rwiper
+//
+void search(uint32_t value)
+{
+  uint32_t t = value;
+  int a = t / LSB_A;
+  t -= a * LSB_A;
+  int b = round(t / LSB_B);
+  R = a * LSB_A + b * LSB_B;
+
+  Serial.print(value);           //  requested R
+  Serial.print('\t');
+  Serial.print(a);               //  position pot A
+  Serial.print('\t');
+  Serial.print(b);               //  position pot B
+  Serial.print('\t');
+  Serial.print(R);               //  effecive R
+  Serial.print('\t');
+  Serial.print(abs(R - value));  //  absolute error
+  Serial.print('\t');
+  Serial.print(100 * abs(R - value) / value);  //  percentage relative error
+  Serial.println();
+}
+
+
+//
+//  prints all possible values
+//  simplified math, ignores Rwiper
+//
+void printTable()
+{
+  for (int a = 0; a < 256; a += 2)
+  {
+    R = a * LSB_A;
+    for (int b = 0; b < 256; b++)
+    {
+      Serial.print(a);
+      Serial.print('\t');
+      Serial.print(b);
+      Serial.print('\t');
+      Serial.print(R);
+      Serial.println();
+      R += LSB_B;
+    }
+  }
+}
+
+//  -- END OF FILE --

libraries/AD524X/keywords.txt

@@ -35,6 +35,6 @@ shutDown	KEYWORD2
 AD524X_LIB_VERSION	LITERAL1
 
 AD524X_OK	LITERAL1
-ADS524X_ERROR	LITERAL1
+AD524X_ERROR	LITERAL1
 AD524X_MIDPOINT	LITERAL1
 

libraries/AD524X/library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/AD524X"
   },
-  "version": "0.5.1",
+  "version": "0.5.2",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",

libraries/AD524X/library.properties

@@ -1,5 +1,5 @@
 name=AD524X
-version=0.5.1
+version=0.5.2
 author=Rob Tillaart <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=Arduino Library for AD524X