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.. _3.1.8_c_mcp3008:

3.1.8 Overheat Monitor(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
-------------------

You may want to make an overheat monitoring device that applies to
various situations, ex., in the factory, if we want to have an alarm and
the timely automatic turning off of the machine when there is a circuit
overheating. In this project, we will use thermistor, joystick, buzzer,
LED and LCD to make an smart temperature monitoring device whose
threshold is adjustable.

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

In this project, we need the following components.

.. image:: img/list2_Overheat_Monitor.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       Pin15    3        22
GPIO23       Pin16    4        23
GPIO24       Pin18    5        24
SDA1         Pin 3             
SCL1         Pin 5             
============ ======== ======== ===

.. image:: img/Schematic_three_one8.png
   :align: center

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

**Step 1:** Build the circuit.

.. image:: img/july24_3.1.8_overheat_monitor_mcp3008.png

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


**Step 2**: Go to the folder of the code.

.. raw:: html

   <run></run>

.. code-block:: 

    cd ~/davinci-kit-for-raspberry-pi/c/3.1.8-2/

**Step 3**: Compile the code.

.. raw:: html

   <run></run>

.. code-block:: 

    gcc 3.1.8_OverheatMonitor.c -lm -lwiringPi

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

.. raw:: html

   <run></run>

.. code-block:: 

    sudo ./a.out

As the code runs, the current temperature and the high-temperature
threshold **40** are displayed on **I2C LCD1602**. If the current
temperature is larger than the threshold, the buzzer and LED are started
to alarm you.

**Joystick** here is for your pressing to adjust the high-temperature
threshold. Toggling the **Joystick** in the direction of X-axis and
Y-axis can adjust (turn up or down) the current high-temperature
threshold. Press the **Joystick** once again to reset the threshold to
initial value.

.. note::

    * If there is an error prompt ``wiringPi.h: No such file or directory``, please refer to :ref:`install_wiringpi`.
    * If you get ``Unable to open I2C device: No such file or directory`` error, you need to refer to :ref:`i2c_config` to enable I2C and check if the wiring is correct.
    * If the code and wiring are fine, but the LCD still does not display content, you can turn the potentiometer on the back to increase the contrast.

Code
----------------------

.. code-block:: c

    #include <wiringPi.h>
    #include <stdio.h>
    #include <wiringPiI2C.h>
    #include <wiringPiSPI.h>
    #include <string.h>
    #include <math.h>

    typedef unsigned char uchar;
    typedef unsigned int  uint;

    #define Joy_BtnPin 3      // GPIO22 -> WiringPi 3
    #define buzzPin    4      // GPIO23 -> WiringPi 4
    #define LedPin     5      // GPIO24 -> WiringPi 5
    #define SPI_CHANNEL 0
    #define SPI_SPEED   1000000

    int LCDAddr    = 0x27;
    int BLEN       = 1;
    int fd;
    int upperTem   = 40;

    // Global variable to store the last joystick change
    int lastJoystickChange = 0;

    int read_ADC(int channel) {
        if (channel < 0 || channel > 7) return -1;
        unsigned char buffer[3];
        buffer[0] = 1;
        buffer[1] = (8 + channel) << 4;
        buffer[2] = 0;
        wiringPiSPIDataRW(SPI_CHANNEL, buffer, 3);
        return ((buffer[1] & 0x03) << 8) | buffer[2];
    }

    void write_word(int data){
        int temp = data;
        if (BLEN)      temp |= 0x08;
        else           temp &= 0xF7;
        wiringPiI2CWrite(fd, temp);
    }

    void send_command(int comm){
        int buf = comm & 0xF0;
        buf |= 0x04; write_word(buf); delay(2); buf &= 0xFB; write_word(buf);
        buf = (comm & 0x0F) << 4;
        buf |= 0x04; write_word(buf); delay(2); buf &= 0xFB; write_word(buf);
    }

    void send_data(int data){
        int buf = data & 0xF0;
        buf |= 0x05; write_word(buf); delay(2); buf &= 0xFB; write_word(buf);
        buf = (data & 0x0F) << 4;
        buf |= 0x05; write_word(buf); delay(2); buf &= 0xFB; write_word(buf);
    }

    void lcd_init(){
        send_command(0x33); delay(5);
        send_command(0x32); delay(5);
        send_command(0x28); delay(5);
        send_command(0x0C); delay(5);
        send_command(0x01); wiringPiI2CWrite(fd, 0x08);
    }

    void lcd_clear(){
        send_command(0x01);
    }

    void write_lcd(int x, int y, const char data[]){
        int addr = 0x80 + 0x40 * y + x;
        send_command(addr);
        for (int i = 0; i < (int)strlen(data); i++)
            send_data(data[i]);
    }

    int get_joystick_value(){
        int x = read_ADC(1);
        int y = read_ADC(2);

        // Dead-band filtering to reduce small fluctuations
        if (x > 900)      return  1;   //    else if (x < 100) return -1;   //     else if (y > 900) return -10;  //     else if (y < 100) return  10;  //    else              return   0; 
    }

    void upper_tem_setting(){
        write_lcd(0,0, "Upper Adjust:");

        int change = get_joystick_value();

        // Only respond to actual direction change
        if (change != 0 && change != lastJoystickChange) {
            upperTem += change;
            lastJoystickChange = change;
        }
        else if (change == 0) {
            // Allow next change after returning to center
            lastJoystickChange = 0;
        }

        // Display current upperTem
        char str[6];
        snprintf(str, sizeof(str), "%d", upperTem);
        write_lcd(0,1, str);
        // Clear remaining LCD characters
        write_lcd(strlen(str),1, "            ");

        delay(100);
    }

    double temperature(){
        int raw = read_ADC(0);
        double Vr = 3.3 * ((double)raw / 1023.0);
        double Rt = 10000.0 * Vr / (3.3 - Vr);
        double tempK = 1.0 / ((log(Rt/10000.0)/3950.0) + 1.0/(273.15+25.0));
        return tempK - 273.15;
    }

    void monitoring_temp(){
        char str[6];
        double cel = temperature();
        snprintf(str, sizeof(str), "%.2f", cel);
        write_lcd(0,0, "Temp: ");
        write_lcd(6,0, str);

        snprintf(str, sizeof(str), "%d", upperTem);
        write_lcd(0,1, "Upper: ");
        write_lcd(7,1, str);
        delay(100);

        if (cel >= upperTem) {
            digitalWrite(buzzPin, HIGH);
            digitalWrite(LedPin,  HIGH);
        } else {
            digitalWrite(buzzPin, LOW);
            digitalWrite(LedPin,  LOW);
        }
    }

    void setup_all(){
        fd = wiringPiI2CSetup(LCDAddr);
        lcd_init();
        if (wiringPiSetup() == -1 ||
            wiringPiSPISetup(SPI_CHANNEL, SPI_SPEED) == -1) {
            printf("Setup failed!\n");
            return;
        }
        pinMode(Joy_BtnPin, INPUT);
        pullUpDnControl(Joy_BtnPin, PUD_UP);
        pinMode(buzzPin, OUTPUT);
        pinMode(LedPin,  OUTPUT);
    }

    int main(void){
        setup_all();

        int lastBtnState = HIGH;
        int stage = 0;

        while (1) {
            int curBtn = digitalRead(Joy_BtnPin);
            // Switch mode when button changes from LOW to HIGH (button released)
            if (curBtn == HIGH && lastBtnState == LOW) {
                stage = (stage + 1) % 2;
                lastJoystickChange = 0;  // Clear debounce status
                delay(100);
                lcd_clear();
            }
            lastBtnState = curBtn;

            if (stage == 1)
                upper_tem_setting();
            else
                monitoring_temp();
        }

        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;
        buffer[1] = (8 + channel) << 4;
        buffer[2] = 0;
        wiringPiSPIDataRW(SPI_CHANNEL, buffer, 3);
        return ((buffer[1] & 0x03) << 8) | buffer[2];
    }

Reads a 10-bit analog value from MCP3008 channel (CH0–CH7) using SPI and returns an integer from 0 to 1023.

.. code-block:: c

    int get_joystick_value() {
        int x = read_ADC(1);
        int y = read_ADC(2);

        if (x > 900)      return 1;   // Right
        else if (x < 100) return -1;  // Left
        else if (y > 900) return -10; // Up
        else if (y < 100) return 10;  // Down
        else              return 0;
    }

Reads joystick X and Y analog values from CH1 and CH2. Returns an integer indicating movement direction based on thresholds.

.. code-block:: c

    void upper_tem_setting() {
        write_lcd(0,0, "Upper Adjust:");

        int change = get_joystick_value();

        if (change != 0 && change != lastJoystickChange) {
            upperTem += change;
            lastJoystickChange = change;
        }
        else if (change == 0) {
            lastJoystickChange = 0;
        }

        char str[6];
        snprintf(str, sizeof(str), "%d", upperTem);
        write_lcd(0,1, str);
        write_lcd(strlen(str),1, "            ");

        delay(100);
    }

Allows user to adjust the upper temperature threshold using the joystick. Prevents repeated changes if direction is held.

.. code-block:: c

    double temperature() {
        int raw = read_ADC(0);
        double Vr = 3.3 * ((double)raw / 1023.0);
        double Rt = 10000.0 * Vr / (3.3 - Vr);
        double tempK = 1.0 / ((log(Rt/10000.0)/3950.0) + 1.0/(273.15+25.0));
        return tempK - 273.15;
    }

Reads analog value from CH0 connected to the thermistor. Uses the Steinhart–Hart equation to calculate Celsius temperature.

.. code-block:: c

    void monitoring_temp() {
        char str[6];
        double cel = temperature();
        snprintf(str, sizeof(str), "%.2f", cel);
        write_lcd(0,0, "Temp: ");
        write_lcd(6,0, str);

        snprintf(str, sizeof(str), "%d", upperTem);
        write_lcd(0,1, "Upper: ");
        write_lcd(7,1, str);
        delay(100);

        if (cel >= upperTem) {
            digitalWrite(buzzPin, HIGH);
            digitalWrite(LedPin,  HIGH);
        } else {
            digitalWrite(buzzPin, LOW);
            digitalWrite(LedPin,  LOW);
        }
    }

Continuously reads the current temperature and displays it along with the threshold. If the temperature exceeds the threshold, the buzzer and LED are activated.

.. code-block:: c

    void setup_all() {
        fd = wiringPiI2CSetup(LCDAddr);
        lcd_init();
        if (wiringPiSetup() == -1 || wiringPiSPISetup(SPI_CHANNEL, SPI_SPEED) == -1) {
            printf("Setup failed!\n");
            return;
        }
        pinMode(Joy_BtnPin, INPUT);
        pullUpDnControl(Joy_BtnPin, PUD_UP);
        pinMode(buzzPin, OUTPUT);
        pinMode(LedPin,  OUTPUT);
    }

Initializes LCD, SPI, GPIO pins for joystick button, buzzer, and LED. Also sets pull-up for the joystick button.

.. code-block:: c

    int main(void) {
        setup_all();

        int lastBtnState = HIGH;
        int stage = 0;

        while (1) {
            int curBtn = digitalRead(Joy_BtnPin);
            if (curBtn == HIGH && lastBtnState == LOW) {
                stage = (stage + 1) % 2;
                lastJoystickChange = 0;
                delay(100);
                lcd_clear();
            }
            lastBtnState = curBtn;

            if (stage == 1)
                upper_tem_setting();
            else
                monitoring_temp();
        }

        return 0;
    }

Main loop switches between two modes:

1. Temperature monitoring.
2. Upper limit adjustment using the joystick.

The mode switches when the joystick button is released (rising edge trigger).


**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**: Go to the folder of the code.

.. raw:: html

   <run></run>

.. code-block:: 

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

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

.. raw:: html

   <run></run>

.. code-block:: 

    sudo python3 3.1.8-2_OverheatMonitor.py

As the code runs, the current temperature and the high-temperature
threshold **40** are displayed on **I2C LCD1602**. If the current
temperature is larger than the threshold, the buzzer and LED are started
to alarm you.

**Joystick** here is for your pressing to adjust the high-temperature
threshold. Toggling the **Joystick** in the direction of X-axis and
Y-axis can adjust (turn up or down) the current high-temperature
threshold. Press the **Joystick** once again to reset the threshold to
initial value.

.. note::

    * If you get the error ``FileNotFoundError: [Errno 2] No such file or directory: '/dev/i2c-1'``, you need to refer to :ref:`i2c_config` to enable the I2C.
    * If you get ``ModuleNotFoundError: No module named 'smbus2'`` error, please run ``sudo apt install python3-smbus2``.
    * If the error ``OSError: [Errno 121] Remote I/O error`` appears, it means the module is miswired or the module is broken.
    * If the code and wiring are fine, but the LCD still does not display content, you can turn the potentiometer on the back to increase the contrast.


.. warning::

    If there is an error prompt  ``RuntimeError: Cannot determine SOC peripheral base address``, please refer to :ref:`faq_soc` 

**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
    import LCD1602

    # GPIO pin definitions
    JOY_BTN_PIN = 22  # Button pin
    BUZZER_PIN = 23   # Buzzer pin
    LED_PIN = 24      # LED pin

    # Initialize GPIO
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(JOY_BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    GPIO.setup(BUZZER_PIN, GPIO.OUT)
    GPIO.setup(LED_PIN, GPIO.OUT)

    # Set initial upper temperature threshold
    upperTem = 40

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

    # Initialize LCD1602
    LCD1602.init(0x27, 1)

    def read_adc(channel):
        """
        Read analog value from MCP3008 (0–7)
        """
        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 get_joystick_value():
        """
        Reads the joystick values and returns a change value based on the joystick's position.
        """
        x_val = read_adc(1)
        y_val = read_adc(2)
        if x_val > 800:
            return 1
        elif x_val < 200:
            return -1
        elif y_val > 800:
            return -10
        elif y_val < 200:
            return 10
        else:
            return 0

    def upper_tem_setting():
        """
        Adjusts and displays the upper temperature threshold on the LCD.
        """
        global upperTem
        LCD1602.write(0, 0, 'Upper Adjust: ')
        change = int(get_joystick_value())
        upperTem += change
        strUpperTem = str(upperTem)
        LCD1602.write(0, 1, strUpperTem)
        LCD1602.write(len(strUpperTem), 1, '              ')
        time.sleep(0.1)

    def temperature():
        """
        Reads the current temperature from the sensor and returns it in Celsius.
        """
        analogVal = read_adc(0)
        Vr = 3.3 * analogVal / 1023.0
        if Vr == 0:
            return 0
        Rt = 10000.0 * (3.3 - Vr) / Vr
        tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
        Cel = tempK - 273.15
        return round(Cel, 2)

    def monitoring_temp():
        """
        Monitors and displays the current temperature and upper temperature threshold. 
        Activates buzzer and LED if the temperature exceeds the upper limit.
        """
        global upperTem
        Cel = temperature()
        LCD1602.write(0, 0, 'Temp: ')
        LCD1602.write(0, 1, 'Upper: ')
        LCD1602.write(6, 0, str(Cel))
        LCD1602.write(7, 1, str(upperTem))
        time.sleep(0.1)
        if Cel >= upperTem:
            GPIO.output(BUZZER_PIN, GPIO.HIGH)
            GPIO.output(LED_PIN, GPIO.HIGH)
        else:
            GPIO.output(BUZZER_PIN, GPIO.LOW)
            GPIO.output(LED_PIN, GPIO.LOW)

    # Main loop
    try:
        lastState = GPIO.input(JOY_BTN_PIN)
        stage = 0
        while True:
            currentState = GPIO.input(JOY_BTN_PIN)
            if currentState == GPIO.HIGH and lastState == GPIO.LOW:
                stage = (stage + 1) % 2
                time.sleep(0.1)
                LCD1602.clear()
            lastState = currentState

            if stage == 1:
                upper_tem_setting()
            else:
                monitoring_temp()

    except KeyboardInterrupt:
        pass

    finally:
        LCD1602.clear()
        GPIO.cleanup()
        spi.close()

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

1. **Import Libraries**

   This section loads the required libraries for GPIO, SPI, LCD display, time delays, and math operations.

   .. code-block:: python

       #!/usr/bin/env python3
       import RPi.GPIO as GPIO
       import spidev
       import time
       import math
       import LCD1602

2. **GPIO and Device Setup**

   Define GPIO pin numbers for the joystick button, buzzer, and LED, and configure GPIO modes.

   .. code-block:: python

       JOY_BTN_PIN = 22  # Button pin
       BUZZER_PIN = 23   # Buzzer pin
       LED_PIN = 24      # LED pin

       GPIO.setmode(GPIO.BCM)
       GPIO.setup(JOY_BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
       GPIO.setup(BUZZER_PIN, GPIO.OUT)
       GPIO.setup(LED_PIN, GPIO.OUT)

3. **SPI and LCD Initialization**

   Start the SPI interface for MCP3008 and initialize the LCD1602 screen with I2C address 0x27.

   .. code-block:: python

       upperTem = 40
       spi = spidev.SpiDev()
       spi.open(0, 0)
       spi.max_speed_hz = 1000000

       LCD1602.init(0x27, 1)

4. **Read ADC Value**

   Reads analog data from MCP3008 ADC via SPI. Channel should be in range 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

5. **Joystick Movement Detection**

   Checks X/Y axis values from the joystick and returns how much to change the threshold.

   .. code-block:: python

       def get_joystick_value():
           x_val = read_adc(1)
           y_val = read_adc(2)
           if x_val > 800:
               return 1
           elif x_val < 200:
               return -1
           elif y_val > 800:
               return -10
           elif y_val < 200:
               return 10
           else:
               return 0

6. **Adjust Upper Temperature Threshold**

   Displays "Upper Adjust" on the LCD and adjusts the threshold using joystick input.

   .. code-block:: python

       def upper_tem_setting():
           global upperTem
           LCD1602.write(0, 0, 'Upper Adjust: ')
           change = int(get_joystick_value())
           upperTem += change
           strUpperTem = str(upperTem)
           LCD1602.write(0, 1, strUpperTem)
           LCD1602.write(len(strUpperTem), 1, '              ')
           time.sleep(0.1)

7. **Temperature Calculation**

   Converts analog sensor reading to voltage, resistance, and finally temperature (Celsius) using Steinhart–Hart approximation.

   .. code-block:: python

       def temperature():
           analogVal = read_adc(0)
           Vr = 3.3 * analogVal / 1023.0
           if Vr == 0:
               return 0
           Rt = 10000.0 * (3.3 - Vr) / Vr
           tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
           Cel = tempK - 273.15
           return round(Cel, 2)

8. **Temperature Monitoring**

   Continuously checks and displays temperature and upper limit. Turns on buzzer and LED if temperature exceeds the threshold.

   .. code-block:: python

       def monitoring_temp():
           global upperTem
           Cel = temperature()
           LCD1602.write(0, 0, 'Temp: ')
           LCD1602.write(0, 1, 'Upper: ')
           LCD1602.write(6, 0, str(Cel))
           LCD1602.write(7, 1, str(upperTem))
           time.sleep(0.1)
           if Cel >= upperTem:
               GPIO.output(BUZZER_PIN, GPIO.HIGH)
               GPIO.output(LED_PIN, GPIO.HIGH)
           else:
               GPIO.output(BUZZER_PIN, GPIO.LOW)
               GPIO.output(LED_PIN, GPIO.LOW)

9. **Main Program Logic**

   Toggles between temperature monitoring and threshold setting modes when the joystick button is pressed.

   .. code-block:: python

       try:
           lastState = GPIO.input(JOY_BTN_PIN)
           stage = 0
           while True:
               currentState = GPIO.input(JOY_BTN_PIN)
               if currentState == GPIO.HIGH and lastState == GPIO.LOW:
                   stage = (stage + 1) % 2
                   time.sleep(0.1)
                   LCD1602.clear()
               lastState = currentState

               if stage == 1:
                   upper_tem_setting()
               else:
                   monitoring_temp()

10. **Cleanup on Exit**

    Ensures proper shutdown of GPIO and SPI resources when Ctrl+C is pressed.

    .. code-block:: python

        except KeyboardInterrupt:
            pass
        finally:
            LCD1602.clear()
            GPIO.cleanup()
            spi.close()