Fix NTCSensor enable pin bug (#1)

* Fix NTC enable pin bug Do not change any pinmodes or values if enablePin is not in use when reading temperature. * Add version history * Update README.md
aattww · Dec 29, 2019 · 13cd353 · 13cd353
1 parent 1292d99
commit 13cd353
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diff --git a/README.md b/README.md
@@ -38,6 +38,7 @@ Skip directly to [Instructions](#instructions), although I strongly recommend re
     * [Battery](#battery-3)
     * [Pulse / Pulse with Kamstrup Multical](#pulse--pulse-with-kamstrup-multical-1)
 * [Instructions](#instructions)
+* [Version history](#version-history)
 
 # External requirements
 
@@ -417,3 +418,13 @@ Place your gateway to a central location and connect it to a Modbus capable netw
 Distribute other nodes as needed, selecting first their addresses with jumper headers and then connecting external power or batteries. Use the button on the nodes to force a transmit with full power - normally nodes adjust their transmit power automatically to the lowest possible level. One blink of the onboard LED indicates a successful transmit, two blinks a failed one. LED blinks only when forcing a transmit with the button. You can use the provided Python script [*read_modbus.py*](read_modbus.py) to read data from the gateway for debugging purposes.
 
 Start logging measurements to a MySQL database ([*save_modbus_to_db.py*](save_modbus_to_db.py) provides a starting point for this), for example, and graph it with [Grafana](https://grafana.com/), or connect the gateway to a home automation hub and monitor measurements that way.
+
+# Version history
+
+## v1.0.1 (2019-12-29)
+
+* Fixed a bug in NTCSensor library where enable pin was controlled even though it was not in actual use, possibly interfering with serial communication.
+
+## v1.0.0 (2019-12-26)
+
+Initial public release.
diff --git a/SensorsGateway/SensorsGateway.ino b/SensorsGateway/SensorsGateway.ino
@@ -61,7 +61,7 @@
 
 
 #define MAJOR_VERSION 1
-#define MINOR_VERSION 1
+#define MINOR_VERSION 2
 
 #include <SimpleModbusAsync.h>
 #include <RH_RF95.h>
@@ -120,7 +120,7 @@ RHReliableDatagram radioManager(rf95Driver);
 SimpleModbusAsync modbus;
 
 // NTC instance
-NTCSensor sensorNTC(0, P3_PIN);
+NTCSensor sensorNTC(NTC_NO_ENABLE_PIN, P3_PIN);
 
 // Memory handler instance
 SensorsMemoryHandler memoryHandler(SRAM_NSS);

diff --git a/SensorsPulse/SensorsPulse.ino b/SensorsPulse/SensorsPulse.ino
@@ -85,7 +85,7 @@
  */
 
 
-#define VERSION 1
+#define VERSION 2
 
 #if defined NODE_TYPE_MULTICAL
 #include <SimpleModbusAsync.h>
@@ -144,7 +144,7 @@ RHReliableDatagram radioManager(rf95Driver);
 SimpleModbusAsync modbus;
 #endif
 
-NTCSensor sensorNTC(0, P3_PIN);
+NTCSensor sensorNTC(NTC_NO_ENABLE_PIN, P3_PIN);
 
 // Payload buffer
 uint8_t payloadBuffer[PAYLOAD_LEN];

diff --git a/libraries/NTCSensor/NTCSensor.cpp b/libraries/NTCSensor/NTCSensor.cpp
@@ -33,27 +33,38 @@
  *
  * Parameters:
  *   enablePin - Enable voltage divider and power on thermistor
- *               255   = Not in use, thermistor is always pulled up by external resistor to Vcc
- *              !=255  = Pin connected to high side of divider
+ *               NTC_NO_ENABLE_PIN = Not in use, thermistor is always pulled up by external resistor to Vcc
+ *               ARDUINO PIN       = Pin connected to high side of divider
  *   sensorPin - Thermistor
  *
- * Schematic (enablePin != 255):
+ * Schematic (enablePin != NTC_NO_ENABLE_PIN):
  * [GND]---[NTC]---|---[SERIES_RESISTOR]---[enablePin]
  *                 |
  *            [sensorPin]
  *
- * Schematic (enablePin == 255):
+ * Schematic (enablePin == NTC_NO_ENABLE_PIN):
  * [GND]---[NTC]---|---[SERIES_RESISTOR]---[Vcc]
  *                 |
  *            [sensorPin]
  */
 
+/*
+ * Version history
+ * ---------------
+ *
+ * 1.1 2019-12-29 (CURRENT)
+ *   - Fixed a bug when enablePin was not in use but placeholder pin was still controlled.
+ *
+ * 1.0 2019-12-26
+ *   Initial public release
+ */
+
 #include "NTCSensor.h"
 
 /*
  * Creates a new instance.
  *
- * enablePin: voltage divider enable pin (set to 255 if not in use)
+ * enablePin: voltage divider enable pin (set to NTC_NO_ENABLE_PIN if not in use)
  * sensorPin: thermistor pin
  *
  * returns:   no
@@ -83,7 +94,7 @@ bool NTCSensor::init() {
   // Go through different scenarios to determine if thermistor is connected properly
 
   // If thermistor does not have a separate enable pin (thermistor should always be powered)
-  if (_enablePin == 255) {
+  if (_enablePin == NTC_NO_ENABLE_PIN) {
     // Enable internal pullup resistor so that pin is not floating if there is no thermistor
     pinMode(_sensorPin, INPUT_PULLUP);
     delay(50);
@@ -136,7 +147,7 @@ bool NTCSensor::init() {
 }
 
 /*
- * Reads current temperature.
+ * Reads current temperature in Celsius.
  *
  * parameters: no
  *
@@ -153,9 +164,11 @@ int16_t NTCSensor::readTemperature() {
   analogReference(DEFAULT);
   analogRead(_sensorPin);
 
-  // Turn on analog voltage divider
-  digitalWrite(_enablePin, HIGH);
-  delay(50);
+  // Turn on analog voltage divider if it is in use
+  if (_enablePin != NTC_NO_ENABLE_PIN) {
+    digitalWrite(_enablePin, HIGH);
+    delay(50);
+  }
 
   float average = 0.0;
 
@@ -165,8 +178,10 @@ int16_t NTCSensor::readTemperature() {
    delay(10);
   }
 
-  // Turn off analog voltage
-  digitalWrite(_enablePin, LOW);
+  // Turn off analog voltage if in use
+  if (_enablePin != NTC_NO_ENABLE_PIN) {
+    digitalWrite(_enablePin, LOW);
+  }
 
   // Calculate average
   average /= 5.0;

diff --git a/libraries/NTCSensor/NTCSensor.h b/libraries/NTCSensor/NTCSensor.h
@@ -33,26 +33,39 @@
  *
  * Parameters:
  *   enablePin - Enable voltage divider and power on thermistor
- *               255   = Not in use, thermistor is always pulled up by external resistor to Vcc
- *              !=255  = Pin connected to high side of divider
+ *               NTC_NO_ENABLE_PIN = Not in use, thermistor is always pulled up by external resistor to Vcc
+ *               ARDUINO PIN       = Pin connected to high side of divider
  *   sensorPin - Thermistor
  *
- * Schematic (enablePin != 255):
+ * Schematic (enablePin != NTC_NO_ENABLE_PIN):
  * [GND]---[NTC]---|---[SERIES_RESISTOR]---[enablePin]
  *                 |
  *            [sensorPin]
  *
- * Schematic (enablePin == 255):
+ * Schematic (enablePin == NTC_NO_ENABLE_PIN):
  * [GND]---[NTC]---|---[SERIES_RESISTOR]---[Vcc]
  *                 |
  *            [sensorPin]
  */
 
+/*
+ * Version history
+ * ---------------
+ *
+ * 1.1 2019-12-29 (CURRENT)
+ *   - Fixed a bug when enablePin was not in use but placeholder pin was still controlled.
+ *
+ * 1.0 2019-12-26
+ *   Initial public release
+ */
+
 #ifndef NTCSENSOR_H
 #define NTCSENSOR_H
 
 #include "Arduino.h"
 
+#define NTC_NO_ENABLE_PIN 255
+
 // Resistance at 25 C
 #define NOMINAL_RESISTANCE 10000.0
 
@@ -69,7 +82,7 @@ class NTCSensor {
 
   private:
 
-    uint8_t _enablePin;  // Voltage divider enable pin (255 if not in use)
+    uint8_t _enablePin;  // Voltage divider enable pin (NTC_NO_ENABLE_PIN if not in use)
     uint8_t _sensorPin;  // Thermistor pin
     bool _initialised;   // Sensor has been initialized
 
@@ -78,7 +91,7 @@ class NTCSensor {
     /*
      * Creates a new instance.
      *
-     * enablePin: voltage divider enable pin (set to 255 if not in use)
+     * enablePin: voltage divider enable pin (set to NTC_NO_ENABLE_PIN if not in use)
      * sensorPin: thermistor pin
      *
      * returns:   no
@@ -99,7 +112,7 @@ class NTCSensor {
     bool init();
 
     /*
-     * Reads current temperature.
+     * Reads current temperature in Celsius.
      *
      * parameters: no
      *