NAME

RPi::Device::SMBus - SMBus/i²c interface for Raspberry Pi

SYNOPSIS

    use RPi::Device::SMBus;

    # Obviously you will need to actually read the data sheet of your device.
    my RPi::Device::SMBus $smbus = RPi::Device::SMBus.new(device => '/dev/i2c-1', address => 0x54);

    $smbus.write-byte(0x10);

    ....

DESCRIPTION

This is an SMBus/i²c interface that has been written and tested for the Raspberry Pi, however it uses a fairly generic POSIX interface so if your platform exposes the i²c interface as a character special device it may work.

In order to use this you will need to install and configure the i2c-dev kernel module and tools. On a default Debian image you should be able to just do:

sudo apt-get install libi2c-dev i2c-tools

And then edit the /etc/modules to add the modules by adding:

i2c-dev
       i2c-bcm2708

And then rebooting.

Typicaly the i2c device will be /dev/i2c-1 on a Raspberry Pi rev B. or v2 or /dev/i2c-0 on older versions.

You can determine the bus address of your device by doing:

sudo i2cdetect -y 1  # replace the 1 with a 0 for older versions

(Obviously the device should be connected, consult the manual for your device about this.)

Which should give you the hexadecimal address of your device. Some devices may not respond, so you may want to either check the data sheet of your device or read the i2cdetect manual page to get other options.

METHODS

Not all devices will necessarily support all of the methods, here. You should consult the data sheet for your device to determine which commands (passed as the Command $command - an unsigned 8 bit integer) should be used as they will differ for all devices.

method new

method new(:$device!, :$address!) returns RPi::Device::SMBus

This is the constructor of the class. The named parameters are both required: device is an the full path (e.g /dev/i2c-1) of the character special device that represents your i2c bus, and address should be the 7 bit numeric address (i.e. an integer less that 128) of the device on the bus.

An exception may be thrown if the device cannot be opened, or it does not support the required ioctls that an i2c device should.

method write-quick

method write-quick(Byte $value) returns Int

This sends a single bit to the device, at the place of the Read/Write bit returning an integer to indicate the result

method read-byte

method read-byte() returns Int

This reads a single byte from the device, without the need to specify a register Command. This may only be implemented by the simplest devices, but it can be used as a short hand for read-byte-data but re-using the previous Command.

method write-byte

method write-byte(Byte $value) returns Int

This is the reverse of read-byte, it will send the single byte to the device.

method read-byte-data

method read-byte-data(Command $command) returns Int

This reads a single byte from the device register specified by $command.

method write-byte-data

method write-byte-data(Command $command, Byte $value) returns Int

This writes the single byte $value to the device register $command, returning an int which will be -1 on failure.

read-word-data

method read-word-data(Command $command) returns Int

This reads the 16 bit word from the register specified by<$command>.

method write-word-data

method write-word-data(Command $command, Word $value) returns Int

This writes the 16 bit word $value to the register specified by $command returning an int (which will be -1 on failure.)

method process-call

method process-call(Command $command, Word $value) returns Int

This writes the 16 bit word $value to the command register $command and then reads it back (presumably the device will have changed it.)

method read-block-data

method read-block-data(Command $command) returns Block

This reads the command register $value and returns the Block (an array containing up to 32 unsigned 8 bit integers.)

method write-block-data

method write-block-data(Command $command, Block $block) returns Int

This writes the Block $block (An array of unsigned bytes,) the the command register $command and returns an integer to indicate the success of the call.

method read-i2c-block-data

method read-i2c-block-data(Command $command, Int $length) returns Block

This is similar to read-block-data but the $length of the number of bytes to be read can be provided, some systems may not support anything other than 32.

method write-i2c-block-data

method write-i2c-block-data(Command $command, Block $block ) returns Int

This is similiar to write-block-data to the extent that the Raku interface is identical.

method block-process-call

method block-process-call(Command $command, Block $block) returns Block

This sends the specified Block (Array of unsigned bytes) to the Command register $command and reads up to 32 bytes back which are returned as a Block