I2C

A class that supports I2C bus.
This specification supports only master devices with 7-bit addresses.
Define two types of methods: convenience methods, which are easy to use, and low-level methods, which provide detailed control.
The low-level methods should be implemented on an as-needed basis, since it is unlikely that they will be needed in most cases.

Constructor

I2C.new( id=nil, *params )

Generates an I2C object by specifying the physical unit indicated by "id."
"id" can be omitted when there is only one physical unit.

Optional Parameters

param	type	description
frequency	Integer	Frequency (default 100kHz)
freq	(Same as above)
scl_pin	---	SCL pin specification
sda_pin	---	SDA pin specification

Example of use:

# Generate an I2C object with the default settings.
i2c = I2C.new()

# Use an I2C device of unit 1 with a frequency of 400kHz.
i2c = I2C.new(1, frequency:400_000 )   # 400kHz

Device-specific

Not all parameters may be supported.

Instance Methods

read( i2c_adrs_7, read_bytes, *param ) -> String

Reads data of read_bytes bytes from the device with the address i2c_adrs_7.
If the device returns NAK in the middle, a String of shorter length than read_bytes may be returned.
If data is specified in the param, it will be output before the repeated start, and then reading will start.
Output specifications are the same as for write().

Example of use:

s = i2c.read( 0x45, 3 )                 # case 1
s = i2c.read( 0x45, 3, 0xf3, 0x2d )     # case 2

I2C bus sequence

(case 1) S -- adrs(45) R A -- data1 A -- data2 A -- data3 A|N -- P
(case 2) S -- adrs(45) W A -- out1(f3) A -- out2(2d) A -- Sr -- adrs(45) R A -- data1 A -- data2 A -- data3 N -- P
    S : Start condition
    P : Stop condition
    Sr: Repeated start condition
    A : Ack
    N : Nack
    R : Read bit
    W : Write bit

write( i2c_adrs_7 , *outputs ) -> Integer

Writes data specified in outputs to the device with the address i2c_adrs_7.
The number of bytes successfully written is returned as the return value.
outputs can be specified as an Integer, Array, or String.

Example of use:

i2c.write( 0x45, 0x30, 0xa2 )
i2c.write( 0x50, 0x00, 0x80, data_string )  # useful for EEPROM
i2c.write( 0x11, [0x30, 0xa2] )

I2C Sequence

S -- adrs W A -- data_1 A -- ... -- data_n N -- P
    S : Start condition
    P : Stop condition
    A : Ack
    N : Nack
    W : Write bit

send_start()

Low level method.
Outputs a StartCondition to the I2C bus.

Example of use:

i2c.send_start

send_restart()

Low level method.
Outputs a Restart (RepeatedStart) Condition to the I2C bus.

Example of use:

i2c.send_restart

send_stop()

Low level method.
Outputs a StopCondition to the I2C bus.

Example of use:

i2c.send_stop

raw_read( read_bytes, ack_nack = false ) -> String

Low level method.
Reads read_bytes bytes from the I2C bus and returns them.
ack_nack = true outputs ACK at the last byte reading, and false outputs NACK.

Example of use:

str = i2c.raw_read( 20 )

raw_write( *outputs ) -> Integer

Low level method.
Writes data specified in outputs to the I2C bus.
The number of bytes successfully written is returned as the return value.
outputs can be specified as an Integer, Array, or String.

Example of use:

i2c.raw_write( 0x45, 0x30, 0xa2 )

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