Add analogue inputs to HAL.

Add ability to read analogue inputs on arduino and on external ADS1115 I2C modules.

IODevice.cpp

@@ -241,6 +241,18 @@ int IODevice::read(VPIN vpin) {
   return false;
 }
 
+// Read analogue value from virtual pin.
+int IODevice::readAnalogue(VPIN vpin) {
+  for (IODevice *dev = _firstDevice; dev != 0; dev = dev->_nextDevice) {
+    if (dev->owns(vpin)) 
+      return dev->_readAnalogue(vpin);
+  }
+#ifdef DIAG_IO
+  //DIAG(F("IODevice::readAnalogue(): Vpin %d not found!"), (int)vpin);
+#endif
+  return false;
+}
+
 
 #else // !defined(IO_NO_HAL)
 
@@ -259,6 +271,13 @@ int IODevice::read(VPIN vpin) {
   pinMode(vpin, INPUT_PULLUP);
   return !digitalRead(vpin);  // Return inverted state (5v=0, 0v=1)
 }
+int IODevice::readAnalogue(VPIN vpin) {
+  pinMode(vpin, INPUT);
+  noInterrupts();
+  int value = analogRead(vpin);
+  interrupts();
+  return value;
+}
 void IODevice::loop() {}
 void IODevice::DumpAll() {
   DIAG(F("NO HAL CONFIGURED!"));
@@ -330,7 +349,7 @@ void ArduinoPins::_write(VPIN vpin, int value) {
   }
 }
 
-// Device-specific read function.
+// Device-specific read function (digital input).
 int ArduinoPins::_read(VPIN vpin) {
   int pin = vpin;
   uint8_t mask = 1 << ((pin-_firstVpin) % 8);
@@ -352,6 +371,39 @@ int ArduinoPins::_read(VPIN vpin) {
   return value;
 }
 
+// Device-specific readAnalogue function (analogue input)
+int ArduinoPins::_readAnalogue(VPIN vpin) {
+  int pin = vpin;
+  uint8_t mask = 1 << ((pin-_firstVpin) % 8);
+  uint8_t index = (pin-_firstVpin) / 8;
+  if (_pinModes[index] & mask) {
+    // Currently in write mode, change to read mode
+    _pinModes[index] &= ~mask;
+    // Since mode changes should be infrequent, use standard pinMode function
+    if (_pinPullups[index] & mask) 
+      pinMode(pin, INPUT_PULLUP);
+    else
+      pinMode(pin, INPUT);
+  }
+  // Since AnalogRead is also called from interrupt code, disable interrupts 
+  // while we're using it.  There's only one ADC shared by all analogue inputs 
+  // on the Arduino, so we don't want interruptions.
+  //******************************************************************************
+  // NOTE: If the HAL is running on a computer without the DCC signal generator,
+  // then interrupts needn't be disabled.  Also, the DCC signal generator puts
+  // the ADC into fast mode, so if it isn't present, analogueRead calls will be much
+  // slower!!
+  //******************************************************************************
+  noInterrupts();
+  int value = analogRead(pin);
+  interrupts();
+
+  #ifdef DIAG_IO
+  //DIAG(F("Arduino Read Pin:%d Value:%d"), pin, value);
+  #endif
+  return value;
+}
+
 void ArduinoPins::_display() {
   DIAG(F("Arduino Vpins:%d-%d"), (int)_firstVpin, (int)_firstVpin+_nPins-1);
 }

IODevice.h

@@ -141,6 +141,9 @@ public:
   // read invokes the IODevice instance's _read method.
   static int read(VPIN vpin);
 
+  // read invokes the IODevice instance's _readAnalogue method.
+  static int readAnalogue(VPIN vpin);
+
   // loop invokes the IODevice instance's _loop method.
   static void loop();
 
@@ -188,12 +191,18 @@ protected:
     return false; 
   }
 
-  // Method to read pin state (optionally implemented within device class)
+  // Method to read digital pin state (optionally implemented within device class)
   virtual int _read(VPIN vpin) { 
     (void)vpin; 
     return 0;
   };
 
+  // Method to read analogue pin state (optionally implemented within device class)
+  virtual int _readAnalogue(VPIN vpin) { 
+    (void)vpin; 
+    return 0;
+  };
+
   // _isBusy returns true if the device is currently in an animation of some sort, e.g. is changing
   //  the output over a period of time.  Returns false unless overridden in sub class.
   virtual bool _isBusy(VPIN vpin) {
@@ -343,8 +352,9 @@ private:
   bool _configure(VPIN vpin, ConfigTypeEnum configType, int paramCount, int params[]) override;
   // Device-specific write function.
   void _write(VPIN vpin, int value) override;
-  // Device-specific read function.
+  // Device-specific read functions.
   int _read(VPIN vpin) override;
+  int _readAnalogue(VPIN vpin) override;
   void _display() override;
 
 

IO_AnalogueInputs.h

@@ -0,0 +1,131 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef io_analogueinputs_h
+#define io_analogueinputs_h
+
+// Uncomment following line to slow the scan cycle down to 1second ADC samples, with
+// diagnostic output of scanned values.
+//#define IO_ANALOGUE_SLOW
+
+#include "IODevice.h"
+#include "I2CManager.h"
+#include "DIAG.h"
+#include "FSH.h"
+
+/**********************************************************************************************
+ * ADS111x class for I2C-connected analogue input modules ADS1113, ADS1114 and ADS1115.
+ * 
+ * ADS1113 and ADS1114 are restricted to 1 input.  ADS1115 has a multiplexer which allows 
+ * any of four input pins to be read by its ADC.
+ * 
+ * The driver polls the device in accordance with the constant 'scanInterval' below.  On first loop
+ * entry, the multiplexer is set to pin A0 and the ADC is triggered.  On second and subsequent
+ * entries, the analogue value is read from the conversion register and then the multiplexer and
+ * ADC are set up to read the next pin.
+ * 
+ * The ADS111x is set up as follows:
+ *    Single-shot scan
+ *    Data rate 128 samples/sec (7.8ms/sample)
+ *    Comparator off
+ *    Gain FSR=6.144V
+ * The gain means that the maximum input voltage of 5V (when Vss=5V) gives a reading 
+ * of 32767*(5.0/6.144) = 26666.
+ * 
+ * Note: The device is simple and does not need initial configuration, so it should recover from
+ * temporary loss of communications or power.
+ **********************************************************************************************/
+class ADS111x: public IODevice { 
+public:
+  ADS111x(VPIN firstVpin, int nPins, uint8_t i2cAddress) {
+    _firstVpin = firstVpin;
+    _nPins = min(nPins,4);
+    _i2cAddress = i2cAddress;
+    _currentPin = _nPins; // Suppress read on first loop entry.
+    addDevice(this);
+  }
+  static void create(VPIN firstVpin, int nPins, uint8_t i2cAddress) {
+    new ADS111x(firstVpin, nPins, i2cAddress);
+  }
+  void _begin() {
+    // Initialise ADS device
+    if (I2CManager.exists(_i2cAddress)) {
+#ifdef DIAG_IO
+      _display();
+#endif
+    } else {
+      DIAG(F("ADS111x device not found, I2C:%x"), _i2cAddress);
+    }
+  }
+  void _loop(unsigned long currentMicros) {
+
+    if (currentMicros - _lastMicros >= scanInterval) {
+      // Check that previous non-blocking write has completed, if not then wait
+      _i2crb.wait();
+
+      // If _currentPin is in the valid range, continue reading the pin values
+      if (_currentPin < _nPins) {
+        _outBuffer[0] = 0x00;  // Conversion register address
+        uint8_t status = I2CManager.read(_i2cAddress, _inBuffer, 2, 1, _outBuffer); // Read register
+        if (status == I2C_STATUS_OK) {
+          _value[_currentPin] = ((uint16_t)_inBuffer[0] << 8) + (uint16_t)_inBuffer[1];
+          #ifdef IO_ANALOGUE_SLOW
+          DIAG(F("ADS111x pin:%d value:%d"), _currentPin, _value[_currentPin]);
+          #endif
+        }
+      }
+      // Move to next pin
+      if (++_currentPin >= _nPins) _currentPin = 0;
+      
+      // Configure ADC and multiplexer for next scan.  See ADS111x datasheet for details
+      // of configuration register settings.
+      _outBuffer[0] = 0x01; // Config register address
+      _outBuffer[1] = 0xC0 + (_currentPin << 4); // Trigger single-shot, channel n
+      _outBuffer[2] = 0x83;           // 128 samples/sec, comparator off
+      // Write command, without waiting for completion.
+      I2CManager.write(_i2cAddress, _outBuffer, 3, &_i2crb);
+
+      _lastMicros = currentMicros;
+    }
+  }
+  int _readAnalogue(VPIN vpin) {
+    int pin = vpin - _firstVpin;
+    return _value[pin];
+  }
+  void _display() {
+    DIAG(F("ADS111x I2C:x%x Configured on Vpins:%d-%d"), _i2cAddress, _firstVpin, _firstVpin+_nPins-1);
+  }
+
+protected:
+  // With ADC set to 128 samples/sec, that's 7.8ms/sample.  So set the period between updates to 10ms
+  #ifndef IO_ANALOGUE_SLOW
+  const unsigned long scanInterval = 10000UL;  // Period between successive ADC scans in microseconds.
+  #else
+  const unsigned long scanInterval = 1000000UL;  // Period between successive ADC scans in microseconds.
+  #endif
+  uint16_t _value[4];
+  uint8_t _i2cAddress;
+  uint8_t _outBuffer[3];
+  uint8_t _inBuffer[2];
+  uint8_t _currentPin;  // ADC pin currently being scanned
+  unsigned long _lastMicros = 0;
+  I2CRB _i2crb;
+};
+
+#endif // io_analogueinputs_h

platformio.ini

@@ -16,6 +16,7 @@ default_envs =
 	unowifiR2
 	nano
 src_dir = .
+include_dir = .
 
 [env]
 build_flags = -Wall -Wextra
@@ -41,7 +42,7 @@ lib_deps =
 	SPI
 monitor_speed = 115200
 monitor_flags = --echo
-build_flags = -DDIAG_IO
+build_flags = -DDIAG_IO -DDIAG_LOOPTIMES
 
 [env:mega2560-no-HAL]
 platform = atmelavr