The twowire command

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Synopsis

twowire subcommand ?arg ...?

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Description

The twowire command provides access to the i2c busses of the Raspberry Pi. The legal values of subcommand are listed below. Note that you can abbreviate the subcommands.

twowire twowire bus address

Create a handle for the i2c device with the specified address on the specified i2c bus. This handle can be used with the other subcommands to exchange data with the device. The regular Tcl close or chan close commands can be used to release the handle.

twowire functionality handle

Check which functionality is supported by the driver. The return value is a list of all supported functions. See the Functionality section below for the possible values.

twowire readbyte handle

Read a single byte from the device addressed by the handle.

twowire readregbyte handle register

Read a byte from the specified register of the device addressed by the handle.

twowire readregword handle register

Read a 2-byte word (LSB, MSB) from the specified register of the device addressed by the handle.

twowire readregblock handle register

Read multiple bytes from the specified register of the device addressed by the handle. The first received data byte is interpreted as the number of data bytes to follow. The data is returned as a binary string.

twowire readregdata handle register length

Read a block of length bytes from the specified register of the device addressed by the handle. The data is returned as a binary string.

twowire writebyte handle data

Write a single byte to the device addressed by the handle.

twowire writeregbyte handle register data

Write a byte to the specified register of the device addressed by the handle.

twowire writeregword handle register data

Write a 2-byte word (LSB, MSB) to the specified register of the device addressed by the handle.

twowire writeregblock handle register bytes

Write a block of data bytes, preceded by the size of the block, to the specified register of the device addressed by the handle. The bytes argument must be a binary string. A maximum of 32 bytes will be written.

twowire writeregdata handle register bytes

Write a block of data bytes to the specified register of the device addressed by the handle. The bytes argument must be a binary string. A maximum of 32 bytes will be written.

Functionality

These are the possible functionality flags that can be reported by the twowire functionality command, along with their meaning. Not all functionalities may be accessible using the twowire command.

readbyte

Handles the readbyte command

writebyte

Handles the writebyte command

readregbyte

Handles the readregbyte command

writeregbyte

Handles the writeregbyte command

readregword

Handles the readregword command

writeregword

Handles the writeregword command

readblock

Handles the readblock command

writeblock

Handles the writeblock command

readdata

Handles the readdata command

writedata

Handles the writedata command

quick

Handles the SMBus write_quick command

notify

Can send the SMBus Host Notify command

proc

Handles the SMBus Process Call command (send 16 bits of data then receive 16 bits of data)

blockproc

Handles the SMBus Block Write - Block Read Process Call (send a block of data, then receive a block of data).

i2c

Plain i2c-level commands (Pure SMBus adapters typically can not do these)

10bitaddr

Handles the 10-bit address extensions

mangling

Knows about the I2C_M_IGNORE_NAK, I2C_M_REV_DIR_ADDR and I2C_M_NO_RD_ACK flags (which modify the I2C protocol!)

pec

Supports Packet Error Checking

nostart

Can skip repeated start sequence

slave

The device operates solely as a slave interface.