From 97622fbe3d1b02b3b38be46f34580f6a17406bdc Mon Sep 17 00:00:00 2001
From: hasenradball <mail@frankhaefele.de>
Date: Fri, 15 Dec 2023 16:52:22 +0100
Subject: [PATCH] add read frequency check

---
 .../AM2302_sensor_health_check.ino                | 15 +++++++++++----
 src/AM2302-Sensor.cpp                             | 13 ++++++++++---
 src/AM2302-Sensor.h                               |  5 ++++-
 3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/examples/AM2302_sensor_health_check/AM2302_sensor_health_check.ino b/examples/AM2302_sensor_health_check/AM2302_sensor_health_check.ino
index 65bf4c5..99921d5 100644
--- a/examples/AM2302_sensor_health_check/AM2302_sensor_health_check.ino
+++ b/examples/AM2302_sensor_health_check/AM2302_sensor_health_check.ino
@@ -20,6 +20,7 @@ void setup() {
    }
    Serial.print(F("\n >>> AM2302-sensor Health Check <<<\n\n"));
 
+   // put your setup code here, to run once:
    // set pin and check for sensor
    if (am2302.begin()) {
       // this delay is needed to receive valid data,
@@ -35,7 +36,7 @@ void setup() {
 }
 
 void loop() {
-  static int checksum_err{0}, timeout_err {0};
+  static int checksum_err{0}, timeout_err {0}, read_freq_err {0};
   // put your main code here, to run repeatedly:
   auto status = am2302.read();
   if (status == AM2302::AM2302_ERROR_CHECKSUM) {
@@ -44,16 +45,22 @@ void loop() {
   if (status == AM2302::AM2302_ERROR_TIMEOUT) {
     ++timeout_err;
   }
+  if (status == AM2302::AM2302_ERROR_READ_FREQ) {
+    ++read_freq_err;
+  }
   Serial.print("\n\n");
-  Serial.print("Sensor status:          ");
+  Serial.print("Sensor status:            ");
   Serial.println(status);
 
-  Serial.print("Number checksum errors: ");
+  Serial.print("Number checksum errors:   ");
   Serial.println(checksum_err);
 
-  Serial.print("Number timeout errors:  ");
+  Serial.print("Number timeout errors:    ");
   Serial.println(timeout_err);
 
+  Serial.print("Number read freq errors:  ");
+  Serial.println(read_freq_err);
+
   Serial.print("\n\n");
   Serial.print("Temperature: ");
   Serial.println(am2302.get_Temperature());
diff --git a/src/AM2302-Sensor.cpp b/src/AM2302-Sensor.cpp
index e97ff0b..f2bcc91 100644
--- a/src/AM2302-Sensor.cpp
+++ b/src/AM2302-Sensor.cpp
@@ -14,7 +14,7 @@
  * 
  * @param pin Pin for AM2302 sensor
  */
-AM2302::AM2302_Sensor::AM2302_Sensor(uint8_t pin) : _pin{pin}
+AM2302::AM2302_Sensor::AM2302_Sensor(uint8_t pin) : _millis_last_read{0}, _pin{pin}
 {}
 
 /**
@@ -28,10 +28,12 @@ bool AM2302::AM2302_Sensor::begin() {
    // required delay() for a secure sensor check,
    // if you reset the mcu very fast one after another
    auto tic{millis()};
-   while ((millis() - tic) < 2000U) {
+   while ( millis() - tic < READ_FREQUENCY ) {
       yield();
    }
-   if (read() == AM2302_READ_OK) {
+   auto status{read()};
+   _millis_last_read = millis();
+   if (status == AM2302_READ_OK) {
       return true;
    }
    else {
@@ -41,6 +43,11 @@ bool AM2302::AM2302_Sensor::begin() {
 
 
 int8_t AM2302::AM2302_Sensor::read() {
+   // check read frequency
+   if ( millis() - _millis_last_read < READ_FREQUENCY) {
+      return AM2302_ERROR_READ_FREQ;
+   }
+   _millis_last_read = millis();
    // *****************************
    //  === send start sequence ===
    // ****************************
diff --git a/src/AM2302-Sensor.h b/src/AM2302-Sensor.h
index 599b1d5..bf08aea 100644
--- a/src/AM2302-Sensor.h
+++ b/src/AM2302-Sensor.h
@@ -18,9 +18,11 @@ namespace AM2302 {
    constexpr int8_t AM2302_READ_OK          {0};
    constexpr int8_t AM2302_ERROR_CHECKSUM   {-1};
    constexpr int8_t AM2302_ERROR_TIMEOUT    {-2};
+   constexpr int8_t AM2302_ERROR_READ_FREQ  {-3};
 
    // define timeout in 100 µs
-   constexpr uint8_t READ_TIMEOUT	{100U};
+   constexpr uint8_t READ_TIMEOUT         {100U};
+   constexpr uint16_t READ_FREQUENCY      {2000U};
 
    class AM2302_Sensor {
 
@@ -32,6 +34,7 @@ namespace AM2302 {
          float get_Humidity() const {return _hum * 0.1F;}
 
       private:
+         unsigned long _millis_last_read;
          uint16_t _hum {0};
          int16_t _temp {0};
          uint8_t _pin;