tasoft / php-i2c-extension
A simple I2C extension for PHP to read from and write to i2c bus.
v1.0.0
2022-06-30 14:45 UTC
Requires
- php: ^7.2
README
I've created this extension to get access to the i2c bus on my raspberry pi.
Installation
$ cd ~
$ git clone https://github.com/tasoftch/php-i2c-extension.git
$ cd php-i2c-extension
$ phpize
$ ./configure --enable-php-i2c
$ make
$ sudo make install
This compiles the source on your machine.
Next find the php.ini file
$ php --ini
Will list scanned ini files.
Add the following line to that php.ini file:
extension=php_i2c
<?php var_dump( extension_loaded('php_i2c') ); // Should be true
Usage
The extension adds five function to the global scope:
i2c_open
This opens the device bus.i2c_select
This selects an address of a connected chip.i2c_read
Reads data from the i2c bus.i2c_write
Writes data to the i2c busi2c_close
Closes the bus.
Example
I've tested with a Raspberry Pi Model B 3+ and the Adafruit ADS1115 analog to digital converter. It's default i2c address is 0x48.
<?php $fd = i2c_open("/dev/i2c-1"); i2c_select($fd, 0x48); for($e=0;$e<30;$e++) { // Read for 30 times the value between channel AIN_0 and GND, 4.096 V, 128 samples/s i2c_write($fd, 1, [0xc3, 0x85]); // Wait for conversion completed usleep(9000); i2c_write($fd, 0); $data = i2c_read($fd, 2); $value = $data[0]*256 + $data[1]; printf("Hex: 0x%02x%02x - Int: %d - Float, converted: %f V\n", $data[0], $data[1], $value, (float)$value*4.096/32768.0); usleep(500000); } i2c_close($fd);
Usage PHP
The package also contains a php wrapper class for i2c.
$ composer require tasoft/php-i2c-extension
Please note that the composer installation does not compile the extension!
For compilation use the installation guide described before.
Now the same example can be rewritten as:
<?php use TASoft\Bus\I2C; $i2c = new I2C(0x48, 1); for($e=0;$e<30;$e++) { // Read for 30 times the value between channel AIN_0 and GND, 4.096 V, 128 samples/s $i2c->write16(1, 0xC385); // Wait for conversion completed usleep(9000); $i2c->writeRegister(0); $value = $i2c->read2Bytes(); printf("Hex: 0x%04x - Int: %d - Float, converted: %f V\n", $value, $value, (float)$value*4.096/32768.0); usleep(500000); }