I2C.py

"""
NI ELVIS III Inter-Integrated Circuit (I2C) Example
This example illustrates how to write data to or read data from an I2C slave
device through the I2C channels. The program first defines the configuration
for the I2C channels, and then writes to and reads from the I2C device. Each
time the write function is called, a list of hexadecimal data is written to
the I2C device; each time the read function is called, a list of data is
returned from the I2C device.

The I2C configuration consists of two parameters: bank and speed. There are two
identical banks of I2C port (A and B). There are two speeds of I2C
communication (standard and fast).

To read data from and write data to the I2C slave device, you must specify an
address in 7 bits. The NI ELVIS III helper library (academicIO) will left
shift the address and insert the read/write bit based on the function called
to match the I2C standard. After that, the original address will become an
8-bit address. The first 7 bits represent the device address and the last bit
represents the mode operation (read mode or write mode).

See https://www.nxp.com/docs/en/user-guide/UM10204.pdf for more details about
I2C.

This example sets the power control register (0x2D) of the ADXL345 device to
measure mode.

See http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf
for more details about ADXL345. See page 25 for more details about the power
control register.

This example uses:
    1. Bank A, I2C.SCL.
    2. Bank A, I2C.SDA.

Hardware setup:
    1. Connect an I2C.SCL of a slave device to I2C.SCL (DIO14) on bank A.
    2. Connect an I2C.SDA of a slave device to I2C.SDA (DIO15) on bank A.
    3. Connect Vcc of a slave device to Vcc (+3.3V) of Bank A.
    4. Connect GND of a slave device to DGND of Bank A.

Result:
    The program sets the power control of the I2C device to measure mode and
    reads back the value from the same register of the I2C slave device for
    validation. The returned value should be 8 in decimal.
"""
import time
from nielvis import I2C, Bank, I2CSpeedMode

# specify the bank
bank = Bank.A
# specify the mode of operation that this program uses to communicate with the
# I2C slave device
speed = I2CSpeedMode.STANDARD

# configure an I2C session
with I2C(bank, speed) as i2c:
    # specify the 7-bit address, in hexadecimal
    # we use the ADXL345 chip for this example and its slave device address is
    # 0x53. You might need to change the slave device address depending on the
    # device you have.
    slave_device_address = 0x53

    # specify the bytes to write to the I2C slave device
    # the first parameter of the write function is 0x2D, which represents the
    # power control register of ADXL345, and the second parameter of the write
    # function is the value to write to the register. 0x08 sets the D3 bit of
    # the power control register to high, which sets the device to measure
    # mode.
    data_to_write = [0x2D, 0x08]
    # write data to the I2C slave device
    i2c.write(slave_device_address, data_to_write)

    # specify the number of bytes to read from the I2C slave device
    number_bytes_to_read = 1
    # read data from the I2C slave device
    return_value = i2c.read(slave_device_address, number_bytes_to_read)
    # print the data
    print(return_value)