MCP3008-I/P 8-Channel 10-Bit A/D Converter

Provides up to 8 channels of 10-bit Analog-to-Digital conversion with SPI interface.

DESCRIPTION

The Microchip MCP3008-I/P provides up to 8 channels of 10-bit Analog-to-Digital conversion with an easy to use SPI interface.

PACKAGE INCLUDES:

• MCP3008-I/P 8-Channel 10-Bit A/D Converter IC

KEY FEATURES OF MCP3008-I/P 8-CHANNEL 10-BIT A/D CONVERTER:

• 10-bit successive approximation A/D converters
• 8 single-ended or 4 differential inputs
• On-chip sample & hold
• Up to 200ksps maximum sampling rate
• Low power
• 2.7-5.5V operation
• Breadboard friendly DIP package

The MCP3008 is an easy way to add A/D capability to an MCU like Raspberry Pi that doesn’t have one or to expand the number of A/D inputs on an MCU like Arduino Uno.

The device uses the SPI interface which allows multiple chips to be put on the same bus with separate Chip Select line enabling the chip being accessed.

The 10-bit matches the bit-depth of built-in A/D converters found on most Arduino and similar MCUs.  For higher bit depth capability, check out the ADS1115 module at the bottom of this page which provides 4 channels of 16-bit using I2C interface.

The part can operate from 2.7- 5.5V and are the DIP version so they are breadboard friendly.

OUR EVALUATION RESULTS:

These parts are very easy to use and have good library support.

The example shown here uses hardware SPI to talk to the MCP3008, but this can be changed to software SPI by uncommenting the line shown in the program.

Since we are using an Uno in our example, the SPI connects to the following pins between the Uno and the IC.  Coincidentally the same pin numbers are used on both.

SPI CLK          Uno pin-13 to IC pin-13
SPI MISO       Uno pin-12 to IC pin-12
SPI MOSI       Uno pin-11 to IC pin-11
SP CS              Uno pin-10 to IC pin-10

Also be sure to wire IC pins 9 & 14 to ground and IC pins 15 & 16 to VCC on the MCU which can either be 3.3V or 5V.

In addition you will need a variable voltage to measure.  We are simply hooking a potentiometer up to the IC pin 1 (A/D CH0) to keep things simple.  You could also just hook it up to the 3.3V output of the MCU.

To use the program you will need to download the MCPXXX.h library using the Arduino IDE.  If you are using a VREF of 3.3V, be sure to change the constant ADC_REF to 3.3 in the program.

Once the program is downloaded and running, open the Serial Monitor window to observe the output which is printed in both the raw ADC reading (0-1024) as well as the calculated voltage.

If you want to optimize the accuracy of the reading, measure the actual voltage at the VREF pin and enter that into the ADC_REF value in place of 5.0.

MCP3008 8-Channel 10-Bit A/D Converter Example Program

/***************************************************
  Example program for MCP3008 A/D converter

  Uses library MCP3XXX.h by Christopher Baker

  Example uses hardware SPI.  For Uno connect the following
  SPI Clock - Pin 13 Uno to Pin 13 IC
  SPI MISO - Pin 12 Uno to Pin 12 IC
  SPI MOSI = Pin 11 Uno to Pin 11 IC
  SPI CS = Pin 10 Uno to Pin 10 IC
  Power to IC pins 15 & 16
  Ground to IC pins 9 & 14
  Pot connected to IC pin 1
 ****************************************************/

#include <MCP3XXX.h>
long const ADC_REF = 5.0;  // Set voltage used for VREF
MCP3008 adc;
//===============================================================================
//  Initialization
//===============================================================================
void setup()
{
  Serial.begin(9600);

  // Use the default SPI hardware interface.
  adc.begin();

  // Or use custom pins to use a software SPI interface.
  // adc.begin(SS, MOSI, MISO, SCK);
}
//===============================================================================
//  Main
//===============================================================================
void loop()
{
  int adc_Reading = adc.analogRead(0);
  Serial.print(adc_Reading);
  Serial.print(" = ");
  Serial.print((adc_Reading * ADC_REF)/1024.0);
  Serial.println("V");
  delay(1000);
}

Notes: 

1. None

TECHNICAL SPECIFICATIONS