John Kemp / mcp3208

A library to interface to the MCP3208 SPI-based ADC from Microchip. This chip provides eight analogue inputs, providing converted 12-bit values via SPI.

Dependents:   Nucleo_MCP3208_Test Nucleo_MCP3208_Ticker_Test BBMv2_eps ref_BBMv2_eps ... more

mcp3208.cpp

Committer:
Kemp
Date:
2011-06-11
Revision:
3:e7de500b1f2d
Parent:
2:93009a423b45

File content as of revision 3:e7de500b1f2d:

#include "mcp3208.h"


#define START_BIT   0x04
#define MODE_SINGLE 0x02    // Single-ended mode
#define MODE_DIFF   0x00    // Differential mode


MCP3208::MCP3208(SPI bus, PinName cs)
    : m_cs(cs), m_bus(bus)
{
    deselect();
}

MCP3208::~MCP3208() {}


void MCP3208::select() {m_cs = 0;}
void MCP3208::deselect() {m_cs = 1; wait_us(1);}


float MCP3208::read_input(int channel)
{
    int command_high = START_BIT | MODE_SINGLE | ((channel & 0x04) >> 2);
    int command_low = (channel & 0x03) << 6;
    
    select();
    
    // Odd writing requirements, see the datasheet for details
    m_bus.write(command_high);
    int high_byte = m_bus.write(command_low) & 0x0F;
    int low_byte = m_bus.write(0);
    
    deselect();
    
    int conv_result = (high_byte << 8) | low_byte;
    
    return ((float)conv_result) / 4096;
}


float MCP3208::read_diff_input(int channel, Polarity polarity)
{
    int command_high = START_BIT | MODE_DIFF | ((channel & 0x02) >> 1);
    int command_low = ((channel & 0x01) << 7) | (polarity << 6);

    select();
    
    // Odd writing and reading requirements, see the datasheet for details.
    m_bus.write(command_high);
    int high_byte = m_bus.write(command_low) & 0x0F;
    int low_byte = m_bus.write(0);
    
    deselect();
    
    int conv_result = (high_byte << 8) | low_byte;
    
    return float(conv_result) / 4096;
}