Overview

"The Microchip MCP3008 ADC is a 10-bit Analog to Digital (A/D) converter with on-board sample and hold circuitry.

Communication with the device is accomplished using a simple serial interface compatible with the SPI protocol. The MCP3008 operates over a broad voltage range (2.7V – 5.5V), and low-current design permits operation with typical standby currents of only 5 nA and typical active currents of 320 µA."

Features

10bit ADC
8 channels
SPI Interface
Sampling Rate: 200kSPS
Supply Voltage 2.7V to 5.5V
Supply Current: 425µA
16 pin DIP
Conversion Time: 10µs

Pinout

Schematics

Pin 9 and 14 linked should be be connected to ground.  VREF (15) and VDD should be connected to your VCC(3.3v)

Sample Code

#include <MCP3008.h>

// define pin connections
#define CS_PIN 12
#define CLOCK_PIN 9
#define MOSI_PIN 11
#define MISO_PIN 10


MCP3008 adc(CLOCK_PIN, MOSI_PIN, MISO_PIN, CS_PIN);

void setup() {
 Serial.begin(9600);
}


void loop() {
  int val = adc.readADC(0); // read Chanel 0 from MCP3008 ADC
  Serial.println(val);
}

Reference