README

PHP library for reading values from the A/D converter MCP3008

Dependencies

The library requires one of the following dependencies to be installed:

berry-spi extension: Native direct communication
volantus/php-pigpio composer library: For using Pigpio daemon socket

Installation

The library may be installed using Composer:

composer require volantus/mcp3008

Usage

All measurements are done through the Reader class.

The constructor requires an SpiInterface object and the ADC reference voltage, which is 3.3 per default on Raspberry.

Using Pigpio daemon (socket)

If you want to use the native SPI channels (recommended), you may use the RegularSpiDevice:

use Volantus\MCP3008\Reader;
use Volantus\Pigpio\Client;
use Volantus\Pigpio\SPI\RegularSpiDevice;

$spiInterface = new RegularSpiDevice(new Client(), 1, 32000, 0);
$reader = new Reader($spiInterface, 3.3);

If you want to use any other GPIO Pins instead, please use the BitBaningSpiDevice:

use Volantus\MCP3008\Reader;
use Volantus\Pigpio\Client;
use Volantus\Pigpio\SPI\BitBangingSpiDevice;

$spiInterface = new BitBangingSpiDevice(new Client(), 12, 16, 20, 21, 32000);
$reader = new Reader($spiInterface, 3.3);

Using direct communication via berry-spi extension:

If you want to use the native SPI channels (recommended), you may use the RegularInterface:

use Volantus\BerrySpi\RegularInterface;
use Volantus\MCP3008\Reader;

$spiInterface = new RegularInterface(1, 32000, 0);
$reader = new Reader($spiInterface, 3.3);

If you want to use any other GPIO Pins instead, please use the BitBangingInterface:

use Volantus\BerrySpi\BitBangingInterface;
use Volantus\MCP3008\Reader;

$spiInterface = new BitBangingInterface(12, 16, 20, 21, 32000, 0);
$reader = new Reader($spiInterface, 3.3);

Reading values

Reading values is done by channel and value is returned as Measurement object:

// Reading value of ADC channel 4
$value = $reader->read(4);

// Getting the raw value, e.g. 789
$value->getRawValue();

// Getting the calculated voltage depending on reference voltage
// e.g. 2.54V in case of 3.3V ref. voltage 
$value->calculateVoltage();

SPI Opening/Closing behaviour

Per default the reader opens the SPI interface in the constructor and closes it in the destructor. But only if needed, so you are free to control it by yourself:

$spiInterface = new RegularInterface(1, 32000, 0);
$spiInterface->open();

$reader = new Reader($spiInterface, 3.3);

$spiInterface->close();
unset($reader);

Contribution

Contribution in form of bug reports, suggestions or pull requests is highly welcome!

volantus / mcp3008

Maintainers

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