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.. _4.1.11_py_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:: ../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:: ../img/schematic_battery_indicator_mcp3008.png
   :align: center

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

**Step 1:** Build the circuit.

.. image:: ../img/july24_3.1.5_battery_indicator_mcp3008.png

**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

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

.. raw:: html

   <run></run>

.. code-block::

    sudo python3 4.1.11-2_BatteryIndicator.py

After the program runs, give the 3rd pin of ADC0834 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``. 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

    # GPIO pins connected to 10 LEDs, ordered from left to right
    led_pins = [25, 12, 16, 20, 21, 5, 6, 13, 19, 26]  # BCM numbering

    # GPIO setup
    GPIO.setmode(GPIO.BCM)
    for pin in led_pins:
        GPIO.setup(pin, GPIO.OUT)
        GPIO.output(pin, GPIO.LOW)

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

    # Read value from MCP3008 channel 
    def read_adc(channel):
        if channel < 0 or channel > 7:
            return -1
        r = spi.xfer2([1, (8 + channel) << 4, 0])
        value = ((r[1] & 0x03) << 8) | r[2]
        return value

    # Light up LED bar graph according to value 
    def led_bar_graph(level):
        for i, pin in enumerate(led_pins):
            if i < level:
                GPIO.output(pin, GPIO.HIGH)
            else:
                GPIO.output(pin, GPIO.LOW)

    # Main loop
    try:
        while True:
            analog_val = read_adc(0)  # Read from MCP3008 channel 0
            level = int(analog_val * 10 / 1023)  
            led_bar_graph(level)
            print(f"ADC: {analog_val}, Level: {level}")
            time.sleep(0.2)

    except KeyboardInterrupt:
        pass

    finally:
        for pin in led_pins:
            GPIO.output(pin, GPIO.LOW)
        GPIO.cleanup()
        spi.close()


Code Explanation
--------------------
This program reads analog voltage from an MCP3008 ADC and displays the result on a 10-LED bar graph using a Raspberry Pi (BCM pin layout).

1. **Import Modules**

   - ``RPi.GPIO`` controls the GPIO pins on Raspberry Pi.
   - ``spidev`` communicates with MCP3008 via SPI.
   - ``time`` provides delay/sleep functionality.

   .. code-block:: python

       #!/usr/bin/env python3

       import RPi.GPIO as GPIO
       import spidev
       import time

2. **GPIO LED Setup**

   A list of 10 GPIO pins is defined for LED control. These pins are configured as output and initialized to LOW (off).

   .. code-block:: python

       # GPIO pins connected to 10 LEDs, ordered from left to right
       led_pins = [25, 12, 16, 20, 21, 5, 6, 13, 19, 26]  # BCM numbering

       GPIO.setmode(GPIO.BCM)
       for pin in led_pins:
           GPIO.setup(pin, GPIO.OUT)
           GPIO.output(pin, GPIO.LOW)

3. **SPI Initialization**

   Initializes SPI bus 0 and chip enable 0 (CE0) to communicate with MCP3008.
   The communication speed is set to 1 MHz.

   .. code-block:: python

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

4. **ADC Read Function**

   Reads an analog value from a specified MCP3008 channel (0–7). The function sends a 3-byte SPI command and decodes the 10-bit result.

   .. code-block:: python

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

5. **LED Bar Graph Function**

   Lights up LEDs based on the analog level. If the level is 7, the first 7 LEDs will be ON and the rest OFF.

   .. code-block:: python

       def led_bar_graph(level):
           for i, pin in enumerate(led_pins):
               if i < level:
                   GPIO.output(pin, GPIO.HIGH)
               else:
                   GPIO.output(pin, GPIO.LOW)

6. **Main Loop**

   Continuously reads analog input from channel 0, scales the result to a value from 0 to 10, and updates the LED display accordingly. Prints ADC and level values for monitoring.

   .. code-block:: python

       try:
           while True:
               analog_val = read_adc(0)
               level = int(analog_val * 10 / 1023)
               led_bar_graph(level)
               print(f"ADC: {analog_val}, Level: {level}")
               time.sleep(0.2)

7. **Cleanup on Exit**

   When ``Ctrl+C`` is pressed, the program turns off all LEDs, cleans up GPIO state, and closes the SPI interface.

   .. code-block:: python

       except KeyboardInterrupt:
           pass

       finally:
           for pin in led_pins:
               GPIO.output(pin, GPIO.LOW)
           GPIO.cleanup()
           spi.close()