coburnw / mcp342x

Python class based access to the MCP3425, MCP3426, MCP3427, and MCP3428 A/D Converters

MCP342x

Simple class based access to the MCP342x series A/D converters in Python

Includes classes for the MCP3425, MCP3426, MCP3427, and MCP3428

quick example:

import time                                                                                           
import mcp342x                                                                           

# get access to a specific device on a bus                                                             
i2c_bus_number = 1
device_address = 0x68
my_adc = mcp342x.Mcp3426(i2c_bus_number, device_address)

# add an input channel to the device                                                                   
channel_number = 0
first_input = mcp342x.Channel(my_adc, channel_number)

#configure channel for 12bit continuous mode and exercise it                                           
print('continuous mode')
first_input.sample_rate = 240
first_input.pga_gain = 1
first_input.continuous = True

first_input.start_conversion() # update device with current channel state and start acquisition        
time.sleep(first_input.conversion_time)
volts = first_input.get_conversion_volts()
print('Chan{}: Volts={}'.format(first_input.number, volts))

Dependencies

• Uses smbus2

Notes

• Tested with both an MCP3426 and MCP3428, primarily in continuous mode, on a raspberry pi zero w.
• Naming conventions follow the Microchip data sheet as best as possible.
• Module does not call time.sleep(). Timing is the responsibility of the application.
• Raises I2CBussError with some help on i2c related OSError.
• Raises ConversionNotReadyError if the not ready flag is found set while reading a conversion.

Todo

• look into passing a smbus2 instance rather than a bus number to Mcp342x.
• identify differences in the MCP3422 group of devices and add overrides for those if possible.

mcp342x's Issues

clunky channel interface

Altho it made sense at the time, the channel interface has always seemed rather clunky to me.
Investigate moving the channel differences of the different chips from the channel class to the adc class.
from:

  adc = mcp342x.Mcp342x(i2c_bus_number, device_address)
  chan = mcp342x.Mcp3427Channel(adc, channel_number)

to:

 adc = mcp342x.Mcp3427(i2c_bus_number, device_address)
 chan = mcp342x.Channel(adc, channel_number)

While we are breaking compatibility, may as well expose the channel_number as 'number' rather than 'channel'.

 print('chan{} = {}volts'.format(chan.number, chan.get_conversion_volts()))

Checkout the rev0 branch if the clunky interface is preferred.