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.. _3.1.4_c_mcp3008:

3.1.4 Smart Fan(MCP3008)
============================

.. note::

   .. image:: img/mcp3008_and_adc0834.jpg
      :width: 25%
      :align: left
    

   Depending on your kit version, please identify whether you have **ADC0834** or **MCP3008** and proceed with the matching section.

Introduction
-----------------

In this project, we will use motors, buttons and thermistors to make a
manual + automatic smart fan whose wind speed is adjustable.

Required Components
------------------------------

In this project, we need the following components. 

.. image:: img/list2_Smart_Fan.png
    :align: center


Schematic Diagram
------------------------

============ ======== ======== ===
T-Board Name physical wiringPi BCM
SPICE0       Pin 24   10       8
SPIMOSI      Pin 19   12       10
SPIMISO      Pin 21   13       9
SPISCLK      Pin 23   14       11
GPIO22       Pin 15   3        22
GPIO5        Pin 29   21       5
GPIO6        Pin 31   22       6
GPIO13       Pin 33   23       13
============ ======== ======== ===

.. image:: img/schematic_3.1.4_smart_fan_mcp3008.png
   :align: center

Experimental Procedures
-----------------------------

**Step 1:** Build the circuit.

.. image:: img/july24_3.1.4_smart_fan_mcp3008.png
    :align: center

.. note::
    The power module can apply a 9V battery with the 9V Battery
    Buckle in the kit. Insert the jumper cap of the power module into the 5V
    bus strips of the breadboard.

.. image:: img/image118.jpeg
    :align: center

**For C Language Users**
^^^^^^^^^^^^^^^^^^^^^^^^^

**Step 2**: Get into the folder of the code.

.. raw:: html

   <run></run>

.. code-block:: 

    cd ~/davinci-kit-for-raspberry-pi/c/3.1.4-2/

**Step 3**: Compile.

.. raw:: html

   <run></run>

.. code-block:: 

    gcc 3.1.4_SmartFan.c -o SmartFan -lwiringPi -lm

**Step 4**: Run the executable file above.

.. raw:: html

   <run></run>

.. code-block:: 

    ./SmartFan

As the code runs, start the fan by pressing the button. Every time you
press, 1 speed grade is adjusted up or down. There are **5** kinds of
speed grades: **0~4**. When set to the 4\ :sup:`th` speed grade and you
press the button, the fan stops working with a **0** wind speed.

Once the temperature goes up or down for more than 2℃, the speed
automatically gets 1-grade faster or slower.

.. note::

    If it does not work after running, or there is an error prompt: \"wiringPi.h: No such file or directory\", please refer to :ref:`install_wiringpi`.

Code
--------

.. code-block:: c

    #include <wiringPi.h>
    #include <wiringPiSPI.h>
    #include <stdio.h>
    #include <softPwm.h>
    #include <math.h>

    #define SPI_CHANNEL 0
    #define SPI_SPEED   1000000
    #define MotorPin1   21
    #define MotorPin2   22
    #define MotorEnable 23
    #define BtnPin      3

    int read_ADC(int channel)
    {
        if (channel < 0 || channel > 7) return -1;

        unsigned char buffer[3];
        buffer[0] = 1;                      // Start bit
        buffer[1] = (8 + channel) << 4;     // Single-ended mode and channel
        buffer[2] = 0;

        wiringPiSPIDataRW(SPI_CHANNEL, buffer, 3);

        int result = ((buffer[1] & 3) << 8) | buffer[2];
        return result;
    }

    int temperture()
    {
        int analogVal = read_ADC(0);
        double Vr = 3.3 * analogVal / 1023.0;  // Use 3.3V as Vref for MCP3008
        double Rt = 10000.0 * Vr / (3.3 - Vr);
        double temp = 1 / (((log(Rt / 10000.0)) / 3950.0) + (1 / (273.15 + 25.0)));
        double cel = temp - 273.15;
        double Fah = cel * 1.8 + 32;
        printf("Celsius: %.2f C  Fahrenheit: %.2f F\n", cel, Fah);
        return (int)cel;
    }

    int motor(int level)
    {
        if (level == 0) {
            digitalWrite(MotorEnable, LOW);
            return 0;
        }
        if (level >= 4) {
            level = 4;
        }
        digitalWrite(MotorEnable, HIGH);
        softPwmWrite(MotorPin1, level * 25);
        return level;
    }

    void setup()
    {
        if (wiringPiSetup() == -1) {
            printf("wiringPi setup failed!\n");
            return;
        }

        if (wiringPiSPISetup(SPI_CHANNEL, SPI_SPEED) == -1) {
            printf("SPI setup failed!\n");
            return;
        }

        softPwmCreate(MotorPin1, 0, 100);
        softPwmCreate(MotorPin2, 0, 100);
        pinMode(MotorEnable, OUTPUT);
        pinMode(BtnPin, INPUT);
    }

    int main(void)
    {
        setup();
        int currentState, lastState = 0;
        int level = 0;
        int currentTemp, markTemp = 0;

        while (1) {
            currentState = digitalRead(BtnPin);
            currentTemp = temperture();

            if (currentTemp <= 0) continue;

            if (currentState == 1 && lastState == 0) {
                level = (level + 1) % 5;
                markTemp = currentTemp;
                delay(500);
            }

            lastState = currentState;

            if (level != 0) {
                if (currentTemp - markTemp <= -2) {
                    level = level - 1;
                    markTemp = currentTemp;
                }
                if (currentTemp - markTemp >= 2) {
                    level = level + 1;
                    markTemp = currentTemp;
                }
            }

            level = motor(level);
        }

        return 0;
    }


Code Explanation
----------------------

.. code-block:: c

    int read_ADC(int channel)
    {
        if (channel < 0 || channel > 7) return -1;

        unsigned char buffer[3];
        buffer[0] = 1;                      // Start bit
        buffer[1] = (8 + channel) << 4;     // Single-ended mode and channel
        buffer[2] = 0;

        wiringPiSPIDataRW(SPI_CHANNEL, buffer, 3);

        int result = ((buffer[1] & 3) << 8) | buffer[2];
        return result;
    }

This function is used to read analog input from MCP3008 on the specified channel.
It sends a 3-byte SPI command and returns a 10-bit digital value between 0–1023.

.. code-block:: c

    int temperture()
    {
        int analogVal = read_ADC(0);
        double Vr = 3.3 * analogVal / 1023.0;  // Use 3.3V as Vref for MCP3008
        double Rt = 10000.0 * Vr / (3.3 - Vr);
        double temp = 1 / (((log(Rt / 10000.0)) / 3950.0) + (1 / (273.15 + 25.0)));
        double cel = temp - 273.15;
        double Fah = cel * 1.8 + 32;
        printf("Celsius: %.2f C  Fahrenheit: %.2f F\n", cel, Fah);
        return (int)cel;
    }

The ``temperture()`` function reads the thermistor analog signal via MCP3008,
calculates voltage, resistance, then converts to Celsius and Fahrenheit using
the thermistor formula (Steinhart–Hart approximation).

.. code-block:: c

    int motor(int level)
    {
        if (level == 0) {
            digitalWrite(MotorEnable, LOW);
            return 0;
        }
        if (level >= 4) {
            level = 4;
        }
        digitalWrite(MotorEnable, HIGH);
        softPwmWrite(MotorPin1, level * 25);
        return level;
    }

This ``motor()`` function controls fan speed via PWM.
Level ranges from 0–4, where 0 turns the fan off and each level increases the duty cycle by 25%.

.. code-block:: c

    void setup()
    {
        if (wiringPiSetup() == -1) {
            printf("wiringPi setup failed!\n");
            return;
        }

        if (wiringPiSPISetup(SPI_CHANNEL, SPI_SPEED) == -1) {
            printf("SPI setup failed!\n");
            return;
        }

        softPwmCreate(MotorPin1, 0, 100);
        softPwmCreate(MotorPin2, 0, 100);
        pinMode(MotorEnable, OUTPUT);
        pinMode(BtnPin, INPUT);
    }

The ``setup()`` function initializes WiringPi, sets up SPI, configures PWM
and GPIO pins needed for motor control and button input.

.. code-block:: c

    int main(void)
    {
        setup();
        int currentState, lastState = 0;
        int level = 0;
        int currentTemp, markTemp = 0;

        while (1) {
            currentState = digitalRead(BtnPin);
            currentTemp = temperture();

            if (currentTemp <= 0) continue;

            if (currentState == 1 && lastState == 0) {
                level = (level + 1) % 5;
                markTemp = currentTemp;
                delay(500);
            }

            lastState = currentState;

            if (level != 0) {
                if (currentTemp - markTemp <= -2) {
                    level = level - 1;
                    markTemp = currentTemp;
                }
                if (currentTemp - markTemp >= 2) {
                    level = level + 1;
                    markTemp = currentTemp;
                }
            }

            level = motor(level);
        }

        return 0;
    }

The ``main()`` function contains the program loop:

1. Constantly checks button state and reads current temperature.
2. On button press, fan level increases (cycles 0–4) and saves temperature.
3. If temperature changes by ±2°C, it auto-adjusts fan speed accordingly.
4. Calls ``motor(level)`` to update PWM output based on current level.



**For Python Language Users**
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

**Step 2:** Set up the SPI interface and install the ``spidev`` library (see :ref:`spi_configuration` for detailed instructions). If you have already completed these steps, you can skip this.

**Step 3**: Get into the folder of the code.

.. raw:: html

   <run></run>

.. code-block:: 

    cd ~/davinci-kit-for-raspberry-pi/python

**Step 4**: Run.

.. raw:: html

   <run></run>

.. code-block:: 

    sudo python3 3.1.4-2_SmartFan.py

As the code runs, start the fan by pressing the button. Every time you
press, 1 speed grade is adjusted up or down. There are **5** kinds of
speed grades: **0~4**. When set to the 4\ :sup:`th` speed grade and you
press the button, the fan stops working with a **0** wind speed.

Once the temperature goes up or down for more than 2℃, the speed
automatically gets 1-grade faster or slower.

Code
--------

.. note::
    You can **Modify/Reset/Copy/Run/Stop** the code below. But before that, you need to go to  source code path like ``davinci-kit-for-raspberry-pi/python``. After modifying the code, you can run it directly to see the effect.

.. raw:: html

    <run></run>

.. code-block:: python

    #!/usr/bin/env python3

    import RPi.GPIO as GPIO
    import spidev
    import time
    import math

    # Pin configuration
    BTN_PIN = 22            # Button GPIO (physical pin 15)
    MOTOR_IN1 = 5           # Motor forward
    MOTOR_IN2 = 6           # Motor backward
    MOTOR_EN = 13           # PWM enable pin

    # GPIO setup
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    GPIO.setup(MOTOR_IN1, GPIO.OUT)
    GPIO.setup(MOTOR_IN2, GPIO.OUT)
    GPIO.setup(MOTOR_EN, GPIO.OUT)

    # PWM setup for motor speed control
    pwm = GPIO.PWM(MOTOR_EN, 1000)  # 1kHz frequency
    pwm.start(0)

    # Initialize SPI for MCP3008
    spi = spidev.SpiDev()
    spi.open(0, 0)  # Bus 0, CE0
    spi.max_speed_hz = 1000000  # 1 MHz

    # Global variables
    level = 0
    currentTemp = 0
    markTemp = 0

    def read_adc(channel):
        if channel < 0 or channel > 7:
            return -1
        adc = spi.xfer2([1, (8 + channel) << 4, 0])
        value = ((adc[1] & 0x03) << 8) | adc[2]
        return value

    def temperature():
        analogVal = read_adc(0)
        Vr = 3.3 * analogVal / 1023.0
        Rt = 10000.0 * Vr / (3.3 - Vr)
        tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
        Cel = tempK - 273.15
        return Cel

    def motor_run(level):
        if level == 0:
            GPIO.output(MOTOR_IN1, GPIO.LOW)
            GPIO.output(MOTOR_IN2, GPIO.LOW)
            pwm.ChangeDutyCycle(0)
            return 0
        if level >= 4:
            level = 4
        GPIO.output(MOTOR_IN1, GPIO.HIGH)
        GPIO.output(MOTOR_IN2, GPIO.LOW)
        pwm.ChangeDutyCycle(level * 25)  # Map level (1–4) to 25%–100%
        return level

    def changeLevel(channel):
        global level, currentTemp, markTemp
        print("Button pressed")
        level = (level + 1) % 5
        markTemp = currentTemp

    # Add event detection for button press
    GPIO.add_event_detect(BTN_PIN, GPIO.FALLING, callback=changeLevel, bouncetime=300)

    def main():
        global level, currentTemp, markTemp
        markTemp = temperature()
        while True:
            currentTemp = temperature()
            if level != 0:
                if currentTemp - markTemp <= -2:
                    level -= 1
                    markTemp = currentTemp
                elif currentTemp - markTemp >= 2:
                    if level < 4:
                        level += 1
                    markTemp = currentTemp
            level = motor_run(level)
            time.sleep(0.2)

    try:
        main()
    except KeyboardInterrupt:
        pass
    finally:
        pwm.stop()
        GPIO.cleanup()
        spi.close()

Code Explanation
---------------------

#. Import required modules:

   - ``RPi.GPIO`` for GPIO control (button and motor),
   - ``spidev`` for communicating with MCP3008 ADC,
   - ``time`` for delays,
   - ``math`` for temperature calculation using logarithmic functions.

   .. code-block:: python

       #!/usr/bin/env python3

       import RPi.GPIO as GPIO
       import spidev
       import time
       import math

#. Set up GPIO pins:

   - Button on GPIO22 (with internal pull-up),
   - Motor control using GPIO5 (forward), GPIO6 (backward), and GPIO13 (PWM enable).

   .. code-block:: python

       BTN_PIN = 22
       MOTOR_IN1 = 5
       MOTOR_IN2 = 6
       MOTOR_EN = 13

       GPIO.setmode(GPIO.BCM)
       GPIO.setup(BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
       GPIO.setup(MOTOR_IN1, GPIO.OUT)
       GPIO.setup(MOTOR_IN2, GPIO.OUT)
       GPIO.setup(MOTOR_EN, GPIO.OUT)

       pwm = GPIO.PWM(MOTOR_EN, 1000)
       pwm.start(0)

#. Initialize SPI communication to the MCP3008 (Bus 0, Chip Enable 0) at 1 MHz.

   .. code-block:: python

       spi = spidev.SpiDev()
       spi.open(0, 0)
       spi.max_speed_hz = 1000000

#. Define ``read_adc()`` function to read a 10-bit analog value (0–1023) from the specified MCP3008 channel (0–7).

   .. code-block:: python

       def read_adc(channel):
           if channel < 0 or channel > 7:
               return -1
           adc = spi.xfer2([1, (8 + channel) << 4, 0])
           value = ((adc[1] & 0x03) << 8) | adc[2]
           return value

#. Define ``temperature()`` function to:

   - Convert analog voltage to resistance,
   - Apply the Steinhart–Hart equation to compute temperature in Celsius.

   .. code-block:: python

       def temperature():
           analogVal = read_adc(0)
           Vr = 3.3 * analogVal / 1023.0
           Rt = 10000.0 * Vr / (3.3 - Vr)
           tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
           Cel = tempK - 273.15
           return Cel

#. Define ``motor_run()`` to:

   - Stop motor at level 0,
   - Run motor forward at increasing speed based on level 1–4, with PWM duty cycle of 25% to 100%.

   .. code-block:: python

       def motor_run(level):
           if level == 0:
               GPIO.output(MOTOR_IN1, GPIO.LOW)
               GPIO.output(MOTOR_IN2, GPIO.LOW)
               pwm.ChangeDutyCycle(0)
               return 0
           if level >= 4:
               level = 4
           GPIO.output(MOTOR_IN1, GPIO.HIGH)
           GPIO.output(MOTOR_IN2, GPIO.LOW)
           pwm.ChangeDutyCycle(level * 25)
           return level

#. Define ``changeLevel()`` callback for button press to:

   - Increase the motor level cyclically (0 to 4),
   - Record the current temperature as the new baseline.

   .. code-block:: python

       def changeLevel(channel):
           global level, currentTemp, markTemp
           print("Button pressed")
           level = (level + 1) % 5
           markTemp = currentTemp

       GPIO.add_event_detect(BTN_PIN, GPIO.FALLING, callback=changeLevel, bouncetime=300)

#. Define ``main()`` loop to:

   - Monitor temperature change relative to the marked temperature,
   - Decrease level if temperature drops by 2°C or more,
   - Increase level if it rises by 2°C or more,
   - Adjust motor speed accordingly every 0.2 seconds.

   .. code-block:: python

       def main():
           global level, currentTemp, markTemp
           markTemp = temperature()
           while True:
               currentTemp = temperature()
               if level != 0:
                   if currentTemp - markTemp <= -2:
                       level -= 1
                       markTemp = currentTemp
                   elif currentTemp - markTemp >= 2:
                       if level < 4:
                           level += 1
                       markTemp = currentTemp
               level = motor_run(level)
               time.sleep(0.2)

#. Run the main function and ensure proper cleanup on Ctrl+C (stop motor, cleanup GPIO, close SPI).

   .. code-block:: python

       try:
           main()
       except KeyboardInterrupt:
           pass
       finally:
           pwm.stop()
           GPIO.cleanup()
           spi.close()