.. _beagley-ai-using-i2c-adc:

Using I2C ADC
##############

Using I2C device on BeagleY-AI is similar to using it on any Raspberry Pi compatible board. 
The image below shows the BeagleY-AI I2C pinout when using 5V for device VCC. 
For more information check `pinout.beagley.ai/pinout/i2c <https://pinout.beagley.ai/pinout/i2c>`_.

.. figure:: ../images/i2c/i2c-pinout-5v.*
    :align: center
    :alt: BeagleY-AI I2C pinout (5V)

    BeagleY-AI I2C pinout (5V)

ADS1115 16-bit ADC
********************

Wiring/connection
==================

Following the I2C pinout shown above let's make the connection of our ADS1115 ADC. 

.. figure:: ../images/i2c/ads1115-connection.*
    :align: center
    :alt: ADS1115 connection

    ADS1115 connection

.. tip:: The ADC can work on ``2.0V - 5.5V`` voltage range, here we have selected to run it on ``5V`` from ``HAT PIN2``. For more information checkout `ADS1115 datasheet <https://www.ti.com/lit/ds/symlink/ads1115.pdf>`_.

To check if your ADS1115 ADC is correctly connected to your BeagleY-AI you can use ``i2cdetect`` command as shown below.

.. code:: console

    i2cdetect -y -r 1

The above command should show ``48`` address occupied in the output, which is the default I2C address of our ADS1115 ADC.

.. code:: console

    debian@BeagleBone:~$ i2cdetect -y -r 1
        0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
    00:                         -- -- -- -- -- -- -- -- 
    10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
    20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
    30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
    40: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- -- 
    50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
    60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
    70: -- -- -- -- -- -- -- --

ADC Parameters
===============

PGA
----

The pga is the programmable gain amplifier (values are full scale), in the device tree overlay we have ``ti,gain = <#>;`` where ``#`` can be following,

- ``0``: +/- 6.144 V
- ``1``: +/- 4.096 V (default)
- ``2``: +/- 2.048 V
- ``3``: +/- 1.024 V
- ``4``: +/- 0.512 V
- ``5``: +/- 0.256 V

Data rate
----------

The data_rate in samples per second, in the device tree overlay we have ``ti,datarate = <#>;`` where ``#`` can be following,

- ``0``: 8
- ``1``: 16
- ``2``: 32
- ``3``: 64
- ``4``: 128
- ``5``: 250
- ``6``: 475
- ``7``: 860 (default)

.. _beagley-ai-adc-ads1115-inputs:

ADC Inputs
-----------

The inputs can be made available by 8 sysfs input files in0_input - in7_input,

- ``in0``: Voltage over AIN0 and AIN1.
- ``in1``: Voltage over AIN0 and AIN3.
- ``in2``: Voltage over AIN1 and AIN3.
- ``in3``: Voltage over AIN2 and AIN3.
- ``in4``: Voltage over AIN0 and GND.
- ``in5``: Voltage over AIN1 and GND.
- ``in6``: Voltage over AIN2 and GND.
- ``in7``: Voltage over AIN3 and GND.

.. note:: In the device tree overlay we have ``channel@4 - channel@7`` device tree nodes representing ``in4 - in7`` from the list above.

.. _beagley-ai-ads1115-using-kernel-driver:

Using kernel driver
===================

To use the kernel driver to drive the ADS1115 ADC, we have created an overlay ``/boot/firmware/overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo``. 
To load the overlay you have to add ``fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo`` to ``/boot/firmware/extlinux/extlinux.conf`` as shown below.

.. code:: text

    ...
    ...
    ...

    label microSD (default)
    kernel /Image
    append console=ttyS2,115200n8 root=/dev/mmcblk1p3 ro rootfstype=ext4 resume=/dev/mmcblk1p2 rootwait net.ifnames=0 quiet
    fdtdir /
    fdt /ti/k3-am67a-beagley-ai.dtb
    fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo

After rebooting the board you should see ``/sys/bus/iio/devices/iio:device0`` available.

.. code:: shell

    debian@BeagleBone:~$ ls /sys/bus/iio/devices/ | grep iio
    iio:device0

To show all the :ref:`beagley-ai-adc-ads1115-inputs` you can create a script called ``adcreader.sh``.

- Create the file,

.. code:: shell

    nano adcreader.sh

- Copy and paste the content below,

.. code:: bash

    in0=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0-voltage1_raw)
    in1=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0-voltage3_raw)
    in2=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage1-voltage3_raw)
    in3=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage2-voltage3_raw)
    in4=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw)
    in5=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage1_raw)
    in6=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage2_raw)
    in7=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage3_raw)

    echo "in0=${in0}\nin1=${in1}\nin2=${in2}\nin3=${in3}\nin4=${in4}\nin5=${in5}\nin6=${in6}\nin7=${in7}"

- To allow the execution of the script as normal user use the command below,

.. code:: shell

    chmod +x adcreader.sh

- To view the ADC updates every 100ms use the ``watch`` command as shown below,

.. code:: shell

    watch -n 0.1 adcreader.sh

The above command should show the values as shown below and it will update them every ``0.1s``,

.. code:: shell

    Every 0.1s: adcreader1.sh

    in0=0
    in1=-2
    in2=2 
    in3=0 
    in4=4447
    in5=4762
    in6=4470
    in7=4696