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RPi_mcp3008 is a library to listen to the MCP3008 A/D converter chip, as described in the datasheet.

Project Description

RPi_mcp3008 is a library to listen to the MCP3008 A/D converter chip with a RPi. This library implements the example communication protocol described in the datasheet.

Communication is made through RPi SPI port using SpiDev

Wiring

Connect the SPI data cables in the tables bellow. Choose either CE0# or CE1# to connect to CS.

RPi SPI GPIOs

RPi GPIO Mode
GPIO 07 CE1#
GPIO 08 CE0#
GPIO 09 MISO
GPIO 10 MOSI
GPIO 11 SCLK

MCP3008 Pinout

Pin Description Pin Description
01 CH0 09 Vdd - Supply voltage (2.7V - 5.5V)
02 CH1 10 Vref - Reference voltage
03 CH2 11 AGND - Analog ground
04 CH3 12 CLK - SPI Clock (SCLK)
05 CH4 13 Dout - Data out (MISO)
06 CH5 14 Din - Data in (MOSI)
07 CH6 15 CS - Chip select (CE0# or CE1#)
08 CH7 16 DGND - Digital ground

Please check the Adafruit guide on the MCP3008 for more information about wiring

Usage

RPi_mcp3008 uses the with statement to properly handle the SPI bus cleanup.

import mcp3008
with mcp3008.MCP3008() as adc:
    print adc.read([mcp3008.CH0]) # prints raw data [CH0]

It’s possible instantiate the object normally, but it’s necessary to call the close method before terminating the program.

import mcp3008
adc = mcp3008.MCP3008()
print adc.read([mcp3008.CH0]) # prints raw data [CH0]
adc.close()

The initialization arguments are MCP3008(bus=0, device=0) where: MCP3008(X, Y) will open /dev/spidev-X.Y, same as spidev.SpiDev.open(X, Y) Both arguments are optional and have a default value of 0

Methods

Currently there are two implemented methods:

def read(self, modes, norm=False):
    '''
    Returns the raw value (0 ... 1024) of the reading.
    The modes argument is a list with the modes of operation to be read (e.g.
    [mcp3008.CH0,mcp3008.Df0]).
    norm is a normalization factor, usually Vref.
    '''
def read_all(self, norm=False):
    '''
    Returns a list with the readings of all the modes
    Data Order:
    [DF0, DF1, DF2, DF3, DF4, DF5, DF6, DF7,
     CH0, CH1, CH2, CH3, CH4, CH5, CH6, CH7]
    norm is a normalization factor, usually Vref.
    '''
  • The modes argument must be a list with at least one of 16 modes listed bellow
  • The norm argument is a normalization factor that rescales raw data, usually Vref

Fixed mode

You can also declare the class with a fixed mode, which will make the instance callable and always return the value of the listed modes. Again you can normalize the data with the norm argument when calling the instance.

import mcp3008
with mcp3008.MCP3008.fixed([mcp3008.CH0, mcp3008.DF0]) as adc:
    print adc()     # prints raw data [CH0, DF0]
    print adc(5.2)  # prints normalized data [CH0, DF0]

MCP3008 Operation Modes

MCP3008 has 16 different operation modes: It can listen to each of the channels individually Single Ended or in a pseudo-differential mode Differential

Single Ended Differential
CH0 DF0 (CH0 = IN+; CH1 = IN-)
CH1 DF0 (CH0 = IN-; CH1 = IN+)
CH2 DF0 (CH2 = IN+; CH3 = IN-)
CH3 DF0 (CH2 = IN-; CH3 = IN+)
CH4 DF0 (CH4 = IN+; CH5 = IN-)
CH5 DF0 (CH4 = IN-; CH5 = IN+)
CH6 DF0 (CH6 = IN+; CH7 = IN-)
CH7 DF0 (CH6 = IN-; CH7 = IN+)

Use the table above as the operation mode when calling MCP3008.read(modes) or setting the MCP3008.fixed(modes) mode. (e.g. MCP3008.read([mcp3008.CH0, mcp3008.DF1]))

Release History

Release History

This version
History Node

0.1a2

History Node

0.1a1

History Node

0.1.0a0

Download Files

Download Files

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File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
mcp3008-0.1a2.tar.gz (4.8 kB) Copy SHA256 Checksum SHA256 Source Dec 13, 2015

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