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.. _4.1.11_py_pi5_mcp3008:

4.1.8 Battery Indicator(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 make a battery indicator device that can
visually display the battery level on the LED Bargraph.

.. warning::

    Do not use battery components that exceed 3.3V to avoid overloading, which may damage the chip or Raspberry Pi.


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

In this project, we need the following components.

.. image:: ../python_pi5/img/list2_Battery_Indicator.png
    :align: center

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Raphael Kit
        - 337
        - |link_Raphael_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 30 20
    :header-rows: 1

    *   - COMPONENT INTRODUCTION
        - PURCHASE LINK

    *   - :ref:`cpn_gpio_board`
        - |link_gpio_board_buy|
    *   - :ref:`cpn_breadboard`
        - |link_breadboard_buy|
    *   - :ref:`cpn_wires`
        - |link_wires_buy|
    *   - :ref:`cpn_resistor`
        - |link_resistor_buy|
    *   - :ref:`cpn_bar_graph`
        - \-
    *   - :ref:`cpn_mcp3008`
        - \-

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
GPIO25       Pin 22   6        25
GPIO12       Pin 32   26       12
GPIO16       Pin 36   27       16
GPIO20       Pin 38   28       20
GPIO21       Pin 40   29       21
GPIO5        Pin 29   21       5
GPIO6        Pin 31   22       6
GPIO13       Pin 33   23       13
GPIO19       Pin 35   24       19
GPIO26       Pin 37   25       26
============ ======== ======== ===

.. image:: ../python_pi5/img/schematic_battery_indicator_mcp3008.png
   :align: center
   :width: 800

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

**Step 1:** Build the circuit.

.. image:: ../python_pi5/img/july24_3.1.5_battery_indicator_mcp3008.png
   :width: 800

**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 ~/raphael-kit/python-pi5

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

.. raw:: html

    <run></run>

.. code-block::

    sudo python3 4.1.11-2_Battery_indicator_zero.py

After the program runs, give the 3rd pin of MCP3008 and the GND a
lead-out wire separately and then lead them to the two poles of a
battery separately. You can see the corresponding LED on the LED
Bargraph is lit up to display the power level (measuring range: 0-5V).

.. 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 ``raphael-kit/python-pi5``. 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 LCD1602
    from gpiozero import LED, Buzzer, Button
    import spidev
    import time
    import math

    # Initialize joystick button, buzzer, and LED
    Joy_BtnPin = Button(22)  # GPIO22, Pin15
    buzzPin = Buzzer(23)     # GPIO23, Pin16
    ledPin = LED(24)         # GPIO24, Pin18

    # Set initial upper temperature threshold
    upperTem = 40

    # Initialize SPI for MCP3008 (Bus 0, CE0 -> GPIO8 / Pin24)
    spi = spidev.SpiDev()
    spi.open(0, 0)
    spi.max_speed_hz = 1000000  # 1 MHz

    # Initialize LCD (I2C address 0x27, backlight on)
    LCD1602.init(0x27, 1)

    def read_adc(channel):
        """
        Read analog value from MCP3008 
        """
        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  # Voltage across the fixed resistor
        if Vr == 0:
            return 0  # Prevent division by zero
        Rt = 10000.0 * (3.3 - Vr) / Vr  # Adjusted formula: thermistor voltage is (3.3 - Vr)
        temp = 1 / (((math.log(Rt / 10000.0)) / 3950.0) + (1 / (273.15 + 25.0)))
        Cel = temp - 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:
            buzzPin.on()
            ledPin.on()
        else:
            buzzPin.off()
            ledPin.off()

    # Main execution loop
    try:
        lastState = 1
        stage = 0
        while True:
            currentState = Joy_BtnPin.value
            if currentState == 1 and lastState == 0:
                stage = (stage + 1) % 2
                time.sleep(0.1)
                LCD1602.clear()
            lastState = currentState
            if stage == 1:
                upper_tem_setting()
            else:
                monitoring_temp()
    except KeyboardInterrupt:
        LCD1602.clear()
        spi.close()


**Code Explanation**

This Python program runs on a Raspberry Pi. It uses an MCP3008 analog-to-digital converter to read temperature data from an analog sensor. A joystick is used to adjust the temperature threshold, and an LCD1602 display shows the current temperature and threshold. A buzzer and LED are triggered when the temperature exceeds the threshold.

1. **Import Required Libraries**

   .. code-block:: python

       #!/usr/bin/env python3

       import RPi.GPIO as GPIO
       import spidev
       import time
       import math
       import LCD1602

   * ``RPi.GPIO`` is used for controlling GPIO pins.
   * ``spidev`` communicates with MCP3008 using SPI.
   * ``math`` is needed for temperature conversion calculations.
   * ``LCD1602`` controls the LCD display.

2. **GPIO Setup**

   .. code-block:: python

       JOY_BTN_PIN = 22
       BUZZER_PIN = 23
       LED_PIN = 24

       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)

   * Assigns pins for joystick button, buzzer, and LED using BCM numbering.
   * Configures the joystick button with a pull-up resistor and sets output pins LOW initially.

3. **SPI and LCD Initialization**

   .. code-block:: python

       upperTem = 40  # Default temperature threshold

       spi = spidev.SpiDev()
       spi.open(0, 0)
       spi.max_speed_hz = 1000000  # 1 MHz

       LCD1602.init(0x27, 1)

   * Initializes SPI communication for the MCP3008.
   * Sets up the I2C LCD1602 at address ``0x27``.

4. **Read ADC Channel**

   .. 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

   * Sends SPI commands to MCP3008 to read analog voltage from the selected channel (0–7).
   * Returns a 10-bit result between 0 and 1023.

5. **Joystick Direction Input**

   .. 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

   * Reads horizontal (X) and vertical (Y) joystick movement and translates that into a change in threshold:

     * Up/Down adjusts by 10.
     * Left/Right adjusts by 1.

6. **Adjust Temperature Threshold**

   .. 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)

   * Allows the user to change the ``upperTem`` threshold via joystick.
   * Updates LCD to display the current threshold value.

7. **Calculate Temperature from Analog Sensor**

   .. 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)

   * Converts voltage reading to resistance, then uses the Steinhart-Hart equation to compute the temperature in Celsius.

8. **Monitoring Mode**

   .. 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)

   * Displays the current temperature and threshold.
   * Activates buzzer and LED if the current temperature exceeds the threshold.

9. **Main Loop**

   .. 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()

   * Uses joystick button press to toggle between:

     * ``stage 0``: temperature monitoring
     * ``stage 1``: threshold adjustment

10. **Cleanup on Exit**

   .. code-block:: python

       except KeyboardInterrupt:
           pass

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

   * Ensures GPIO and LCD are reset on program termination (e.g., Ctrl+C).