refactor #78, redo #76 (#79)

- Fix #78, prevent infinite loop. (Thanks to devmirek).
- Fix #76 (again), update readme.md Comparator Polarity.
- add ADS1X15_ERROR_I2C, communication error.
- add minimal section in readme.md about error codes.
- minor edits.

ADS1X15.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: ADS1X15.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.4
+// VERSION: 0.4.5
 //    DATE: 2013-03-24
 // PURPOSE: Arduino library for ADS1015 and ADS1115
 //     URL: https://github.com/RobTillaart/ADS1X15
@@ -183,8 +183,8 @@ uint8_t ADS1X15::getGain()
     case ADS1X15_PGA_0_512V: return 8;
     case ADS1X15_PGA_0_256V: return 16;
   }
-  _err = ADS1X15_INVALID_GAIN;
-  return _err;
+  _error = ADS1X15_INVALID_GAIN;
+  return _error;
 }
 
 
@@ -219,8 +219,8 @@ float ADS1X15::getMaxVoltage()
     case ADS1X15_PGA_0_512V: return 0.512;
     case ADS1X15_PGA_0_256V: return 0.256;
   }
-  _err = ADS1X15_INVALID_VOLTAGE;
-  return _err;
+  _error = ADS1X15_INVALID_VOLTAGE;
+  return _error;
 }
 
 
@@ -242,8 +242,8 @@ uint8_t ADS1X15::getMode(void)
     case ADS1X15_MODE_CONTINUE: return 0;
     case ADS1X15_MODE_SINGLE:   return 1;
   }
-  _err = ADS1X15_INVALID_MODE;
-  return _err;
+  _error = ADS1X15_INVALID_MODE;
+  return _error;
 }
 
 
@@ -402,8 +402,8 @@ int16_t ADS1X15::getComparatorThresholdHigh()
 
 int8_t ADS1X15::getError()
 {
-  int8_t rv = _err;
-  _err = ADS1X15_OK;
+  int8_t rv = _error;
+  _error = ADS1X15_OK;
   return rv;
 }
 
@@ -451,11 +451,17 @@ int16_t ADS1X15::_readADC(uint16_t readmode)
   _requestADC(readmode);
   if (_mode == ADS1X15_MODE_SINGLE)
   {
-    unsigned long start = millis();
-    while (isBusy()) {
+    uint32_t start = millis();
+    //  timeout == { 129, 65, 33, 17, 9, 5, 3, 2 }
+    //  a few ms more than max conversion time.
+    uint8_t timeOut = (128 >> (_datarate >> 5)) + 1;
+    while (isBusy())
+    {
       yield();   //  wait for conversion; yield for ESP.
-      if ((start + ADS1X15_READ_TIMEOUT_MS) < millis())
+      if ( (millis() - start) > timeOut)
+      {
         return ADS1X15_ERROR_TIMEOUT;
+      }
     }
   }
   else
@@ -485,7 +491,7 @@ void ADS1X15::_requestADC(uint16_t readmode)
   _writeRegister(_address, ADS1X15_REG_CONFIG, config);
 
   //  remember last request type.
-    _lastRequest = readmode;
+  _lastRequest = readmode;
 }
 
 
@@ -495,23 +501,32 @@ bool ADS1X15::_writeRegister(uint8_t address, uint8_t reg, uint16_t value)
   _wire->write((uint8_t)reg);
   _wire->write((uint8_t)(value >> 8));
   _wire->write((uint8_t)(value & 0xFF));
-  return (_wire->endTransmission() == 0);
+  int rv = _wire->endTransmission();
+  if (rv != 0) 
+  {
+    _error =  ADS1X15_ERROR_I2C;
+    return false;
+  }
+  return true;
 }
 
 
 uint16_t ADS1X15::_readRegister(uint8_t address, uint8_t reg)
 {
   _wire->beginTransmission(address);
   _wire->write(reg);
-  _wire->endTransmission();
-
-  int rv = _wire->requestFrom((int) address, (int) 2);
-  if (rv == 2)
+  int rv = _wire->endTransmission();
+  if (rv == 0) 
   {
-    uint16_t value = _wire->read() << 8;
-    value += _wire->read();
-    return value;
+    rv = _wire->requestFrom((int) address, (int) 2);
+    if (rv == 2)
+    {
+      uint16_t value = _wire->read() << 8;
+      value += _wire->read();
+      return value;
+    }
   }
+  _error =  ADS1X15_ERROR_I2C;
   return 0x0000;
 }
 
@@ -742,3 +757,4 @@ void ADS1115::requestADC_Differential_2_3()
 
 
 //  -- END OF FILE --
+

ADS1X15.h

@@ -2,7 +2,7 @@
 //
 //    FILE: ADS1X15.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.4
+// VERSION: 0.4.5
 //    DATE: 2013-03-24
 // PURPOSE: Arduino library for ADS1015 and ADS1115
 //     URL: https://github.com/RobTillaart/ADS1X15
@@ -12,7 +12,7 @@
 #include "Arduino.h"
 #include "Wire.h"
 
-#define ADS1X15_LIB_VERSION               (F("0.4.4"))
+#define ADS1X15_LIB_VERSION               (F("0.4.5"))
 
 //  allow compile time default address
 //  address in { 0x48, 0x49, 0x4A, 0x4B }, no test...
@@ -24,13 +24,11 @@
 #define ADS1115_ADDRESS                   0x48
 #endif
 
-#ifndef ADS1X15_READ_TIMEOUT_MS
-#define ADS1X15_READ_TIMEOUT_MS           200 //Longest acquisition time is 125ms (8SPS)
-#endif
 
 #define ADS1X15_OK                        0
 #define ADS1X15_INVALID_VOLTAGE           -100
 #define ADS1X15_ERROR_TIMEOUT             -101
+#define ADS1X15_ERROR_I2C                 -102
 #define ADS1X15_INVALID_GAIN              0xFF
 #define ADS1X15_INVALID_MODE              0xFE
 
@@ -198,7 +196,7 @@ class ADS1X15
   void     _requestADC(uint16_t readmode);
   bool     _writeRegister(uint8_t address, uint8_t reg, uint16_t value);
   uint16_t _readRegister(uint8_t address, uint8_t reg);
-  int8_t   _err = ADS1X15_OK;
+  int8_t   _error = ADS1X15_OK;
 
   TwoWire*  _wire;
   uint32_t  _clockSpeed = 0;
@@ -272,3 +270,4 @@ class ADS1115 : public ADS1X15
 
 
 //  -- END OF FILE --
+

CHANGELOG.md

@@ -5,6 +5,13 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.4.5] - 2024-07-03
+- Fix #78, prevent infinite loop. (Thanks to devmirek).
+- Fix #76 (again), update readme.md Comparator Polarity.
+- add ADS1X15_ERROR_I2C, communication error.
+- add minimal section in readme.md about error codes.
+- minor edits.
+
 ## [0.4.4] - 2024-06-28
 - Fix #76, update readme.md Comparator Polarity
 - added defines to replace magic numbers (not used in code yet)

README.md

@@ -474,26 +474,33 @@ Flag is only explicitly set after a **readADC()** or a **requestADC()**
 - **uint8_t getComparatorPolarity()** returns value set.
 
 
-From tests (#76) it became clear that the behaviour of the **ALERT/RDY** pin is a bit ambiguous.
-The meaning of HIGH LOW is different for **continuous** and **single** mode, see
-the table below. Also different is the timing of the pulse at the **ALERT/RDY** pin.
-See **ADS_COMP_POL.ino**.
+From tests (see #76) it became clear that the behaviour of the **ALERT/RDY** pin 
+looks ambiguous. Further investigation eventually showed that the behaviour is 
+logical but one should not think in "pulses", more in levels and edges.
 
-Timing of pulse from a synchronous ```ADS.readADC(0)``` call.
+In the continuous mode it looks like an 8us pulse, however this "pulse" is
+actual a short time (8 us) of IDLE followed by a long time pulse of converting.
+
+In the single shot mode it looks like the converting time is the pulse
+as that is the only single change visible. This is IMHO the correct view.
+
+
+#### ALERT RDY table
+
+|  MODE          |  COMP_POL  |  IDLE  |  START    |  CONVERT  |   READY   |
+|:---------------|:-----------|:-------|:----------|:----------|:----------|
+| 0 = continuous |  0 = LOW   |  HIGH  |  FALLING  |  LOW      |  RISING   |
+| 0 = continuous |  1 = HIGH  |  LOW   |  RISING   |  HIGH     |  FALLING  |
+| 1 = single     |  0 = LOW   |  HIGH  |  FALLING  |  LOW      |  RISING   |
+| 1 = single     |  1 = HIGH  |  LOW   |  RISING   |  HIGH     |  FALLING  |
 
-| TEST |  MODE            |  COMP_POL  |  ALERT/RDY PIN                |  Notes  |
-|:----:|:-----------------|:-----------|:------------------------------|:--------|
-|   1  |  0 = continuous  |  0 = LOW   |  LOW with 8 us HIGH pulse     |  as specified in datasheet
-|   2  |  0 = continuous  |  1 = HIGH  |  HIGH with 8 us LOW pulse     |  as specified in datasheet
-|   3  |  1 = single      |  0 = LOW   |  HIGH with an 8 ms LOW pulse  |  depends on data rate
-|   4  |  1 = single      |  1 = HIGH  |  LOW with an 8 ms HIGH pulse  |  depends on data rate
 
 See issue #76 for some screenshots.
 
 
-#### Effect Data Rate
+#### Converting time by Data Rate
 
-|  data rate  |  pulse length  |  Notes  |
+|  data rate  |  convert time  |  Notes  |
 |:-----------:|:--------------:|:-------:|
 |      0      |     125 ms     |
 |      1      |      62 ms     |
@@ -509,14 +516,25 @@ Times are estimates from scope.
 
 #### Conclusions
 
-- Conversion always generates a pulse.
-- The length of the pulse in continuous mode and in single mode differs.
-  - In single shot mode the length of the pulse indicates the conversion time.
-  - In continuous mode the pulse indicates the end of conversion.
-- The polarity in single mode seems to have an inverted pulse, however it is
-  not about the pulse, it is about the edge.
-- If COMP_POL = 0, a FALLING edge indicates conversion ready.
-- If COMP_POL = 1, a RISING edge indicates conversion ready. 
+- Conversion generates a conversion pulse with length depending on the data rate.
+- In continuous mode it looks like there is a short pulse, but actual the long
+  period is the conversion pulse. 
+
+In short:
+
+- if COMP_POL = 0, 
+  - a FALLING edge indicates conversion start.
+  - a LOW level indicates converting.
+  - a RISING edge indicates conversion ready.
+  - a HIGH level indicates idle.
+ 
+- if COMP_POL = 1, 
+  - a RISING edge indicates conversion start.
+  - a HIGH level indicates converting.
+  - a FALLING edge indicates conversion ready.
+  - a LOW level indicates idle.
+
+This interpretation is in line with all tests done in #76.
 
 
 ### Latch
@@ -568,6 +586,23 @@ mean something different see - Comparator Mode above or datasheet.
 - **int16_t getComparatorThresholdHigh()** reads value from device.
 
 
+## Error codes
+
+This section has to be elaborated.
+
+Some functions return or set an error value.
+This is read and reset by **getError()** 
+
+|  Value  |  Define                   |  Description  |
+|:-------:|:-------------------------:|:-------------:|
+|      0  |  ADS1X15_OK               | idem.
+|   -100  |  ADS1X15_INVALID_VOLTAGE  | getMaxVoltage()
+|   -101  |  ADS1X15_ERROR_TIMEOUT    | readADC() device did not respond in time.
+|   -102  |  ADS1X15_ERROR_I2C        | I2C communication failure.
+|   0xFF  |  ADS1X15_INVALID_GAIN     | getGain() 
+|   0xFE  |  ADS1X15_INVALID_MODE     | getMode()
+
+
 ## Future ideas & improvements
 
 #### Must
@@ -580,10 +615,11 @@ mean something different see - Comparator Mode above or datasheet.
 - Remove the experimental **getWireClock()** as this is not really a library function
   but a responsibility of the I2C library.
 - Investigate ADS1118 library which should be a similar SPI based ADC.
+- improve error handling
+  - refactor values to be more logic.
 
 #### Could
 
-- More examples
 - SMB alert command (00011001) on I2C bus?
 - Sync code order .h / .cpp
 

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/ADS1X15"
   },
-  "version": "0.4.4",
+  "version": "0.4.5",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=ADS1X15
-version=0.4.4
+version=0.4.5
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for ADS1015 - I2C 12 bit ADC and ADS1115 I2C 16 bit ADC