new example - flashes sensor led based on % of moisture detected

Author: gigapod

examples/Example_03_LEDFlashMoisture/Example_03_LEDFlashMoisture.ino

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+/*
+*---------------------------------------------------------------------------------
+ *
+ * Copyright (c) 2025, SparkFun Electronics Inc.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ *---------------------------------------------------------------------------------
+ */
+
+// This example demonstrates how to read the soil moisture sensor and control the on-board LED.
+// The LED flash rate is based on how "wet" the soil is. The drier the soil, the faster the LED flashes.
+
+#include "SparkFun_Soil_Moisture_Sensor.h" // CTRL+Click here to get the library: http://librarymanager/All#SparkFun_Soil_Moisture_Sensor
+#include <Wire.h>
+
+SparkFunSoilMoistureSensor mySoilSensor; // Create an instance of the sensor class
+
+// The plan:
+//    The value of the sensor has the following range:
+//       0    = 100% wet soil (no resistance)
+//       1024 = 0% wet soil (infinite resistance) note: the sensors ADC is 10-bit 2^10 = 1024
+//
+//    The LED will flash faster the drier the soil is. The LED will be effectively off when the soil is 100% wet.
+//
+// The flash rate is:
+//  0% Wet = 1 flash every <fast_value> seconds
+/// 10%-90% Wet = rate proportional to the percentage of wetness
+//  100% Wet = off
+//
+// To do this, the following is done:
+//  1. Read the sensor value
+//  2. Calculate the percentage of wetness and multiply by 10 using integer math (floor)- this gives a value of 0 to 10
+//  3. The LED flash_rate = value * increment_value, if value is 0, rate = <fast_value> seconds a value of 1 second for 0% wetness and 
+//    "off" for > 90% wetness
+
+
+
+// Define our max dry value - note using a float here 
+#define MAX_DRY_VALUE 1024.0
+
+// Min flash rate in ms (2 seconds)
+#define FAST_FLASH_RATE 2000
+
+// Max flash rate in ms (1 day) - basically off
+#define MAX_FLASH_RATE 86400000
+
+// Define our increment value = 10000ms (10 seconds)
+#define FLASH_INCREMENT 10000
+
+// Time between loop iterations - 5 second (should not be greater that FAST_FLASH_RATE)
+#define LOOP_DELAY FAST_FLASH_RATE
+
+// Define a variable for the last blink time - in ms since boot
+uint32_t lastBlinkTime = 0;
+
+// Define a variable for the blink rate - delay between blinks in ms
+uint32_t blinkRate = 0;
+
+// Some Dev boards have their QWIIC connector on Wire or Wire1
+// This #ifdef will help this sketch work across more products
+
+#ifdef ARDUINO_SPARKFUN_THINGPLUS_RP2040
+#define wirePort Wire1
+#else
+#define wirePort Wire
+#endif
+
+//----------------------------------------------------------------------------------------
+void setup()
+{
+
+    // Set up the serial port for output
+    Serial.begin(115200);
+
+    while (!Serial)
+        delay(10); // Wait for Serial to become available.
+    // Necessary for boards with native USB (like the SAMD51 Thing+).
+    // For a final version of a project that does not need serial debug (or a USB cable plugged in),
+    // Comment out this while loop, or it will prevent the remaining code from running.
+
+    // print out the startup banner
+    Serial.println();
+    Serial.println("------------------------------------------------------------");
+    Serial.println("SparkFun Soil Sensor Example 3");
+    Serial.println("Blink sensor LED based on soil moisture percentage");
+    Serial.println("------------------------------------------------------------");
+    Serial.println();
+
+    // start the I2C bus
+    wirePort.begin();
+
+    // Check if the sensor is connected and initialize it
+    if (mySoilSensor.begin() == false)
+    {
+        Serial.println("Soil Moisture Sensor not detected at default I2C address. Verify the sensor is connected. Stopping.");
+                       
+        while (1)
+            ;
+    }
+
+    Serial.println("Soil Moisture Sensor found!");
+
+    // print out the LED flash rate information
+    Serial.println();
+    Serial.println("LED will flash based on the soil moisture reading:");
+    Serial.print("  < 10% Wet = 1 flash every ");
+    Serial.print(FAST_FLASH_RATE/1000);
+    Serial.println(" seconds");
+    Serial.print("  10%-90% Wet = flash rate proportional to the percentage of wetness: ");
+    Serial.print(FLASH_INCREMENT/1000);
+    Serial.println(" seconds per 10% range");
+    Serial.println("  > 90% Wet = LED off");
+    Serial.println();
+
+    mySoilSensor.LEDOff();
+
+    // setup the initial blink rate bin - off 
+    blinkRate= MAX_FLASH_RATE;
+
+    // initial last blink time - now!
+    lastBlinkTime = millis(); 
+
+    Serial.println("Reading soil moisture sensor...");
+    Serial.println();
+
+
+}
+
+//----------------------------------------------------------------------------------------
+void loop()
+{
+    // Let's get the soil moisture reading
+    uint16_t soilMoisture = mySoilSensor.readMoistureValue();
+
+    // Wet ration 0 - 1.0
+    float wetRatio = ((MAX_DRY_VALUE   - (float)soilMoisture) / MAX_DRY_VALUE);
+
+    // Output the value:
+    Serial.print("Soil Moisture: ");
+    Serial.print(soilMoisture);
+    Serial.print(" (sensor value), ");
+    Serial.print(wetRatio * 100);
+    Serial.println("% wet");
+
+    // Update the blink rate based on the soil moisture reading
+    updateBlinkRate(wetRatio);
+    
+    // check if we need to flash the LED
+    checkForLEDBlink();
+    
+    // delay our reading.
+    delay(LOOP_DELAY);
+}
+
+//----------------------------------------------------------------------------------------
+// A function to update the blink rate based on the soil moisture ration (0 - 1.0)
+void updateBlinkRate(float wetRatio)
+{
+
+    // Calculate the delay rate "bin" (wet ratio * 10) for the LED based on this current reading
+    // The rate bin is a value from 0 to 10
+    uint32_t blinkRateBin =  wetRatio * 10;
+
+    // What is the blink rate in ms?
+    if (blinkRateBin == 0)
+    {
+        // 0% wet - Flash at the fast rate
+        blinkRate = FAST_FLASH_RATE;
+    }
+    else if (blinkRateBin > 8)
+    {
+        // 90% - 100% wet - LED off
+        blinkRate = MAX_FLASH_RATE; // 1 day - basically off
+    }else {
+        // 10%-90% wet - rate proportional to the percentage of wetness
+        blinkRate = blinkRateBin * FLASH_INCREMENT;
+    }
+
+}
+
+//----------------------------------------------------------------------------------------
+// A function to check if we need to flash the LED based on elapsed time from last blink
+void checkForLEDBlink(void )
+{
+    // do we need to flash the LED?
+    if (millis() - lastBlinkTime > blinkRate)
+    {
+        // Wink the LED during the reading
+        mySoilSensor.LEDOn();
+        delay(100);
+        mySoilSensor.LEDOff();
+
+        lastBlinkTime = millis();
+    }
+}