I've created this extension to get access to the i2c bus on my raspberry pi.
- The development module for your version of PHP, i.e, php7.4-dev, php8.2-dev.
Change the configure file on line 5 (php-config7.4), to match your installed version of PHP. Then, run the following commands to install the extension.
$ cd ~
$ git clone https://github.com/tasoftch/php-i2c-extension.git
$ cd php-i2c-extension
$ phpize
$ ./configure --with-php-config=/usr/bin/php-config7.4 --enable-php-i2c
$ make
$ sudo make install
Next, find the location of PHP's INI files on your computer by running the following command.
$ php --ini | grep -i "Configuration File.*Path"
Note: If you're using Microsoft Windows, then run php --ini and look for the value of "Configuration File (php.ini) Path:".
You should see a directory path such as /etc/php/7.4/cli. In that directory, create a new INI file named 20-i2c.ini with the following contents
; configuration for php i2c module
extension=php_i2cThen, with the file created, test that the I2C extension is loaded by running the following command:
php --ri php_i2cYou should see the following output:
php_i2c
Version => 0.8.0The 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_readi2c_read_bytei2c_read_2_bytesi2c_read_3_bytesi2c_read_4_bytes
Reads data from the i2c bus.i2c_writei2c_write_bytei2c_write_2_bytesi2c_write_3_bytesi2c_write_4_bytes
Writes data to the i2c busi2c_close
Closes the bus.
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]);
// or
// i2c_write_2_bytes( 0x01c385 );
// 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);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);
$value = $i2c->readRegister16(1);
printf("Hex: 0x%04x - Int: %d - Float, converted: %f V\n",
$value, $value, (float)$value*4.096/32768.0);
usleep(500000);
}
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