DS28E17IIC(4)

NAME
ds28e17iic - Driver for Maxim DS28E17 1-Wire to I2C bridge

SYNOPSIS
ds28e17iic* at onewire?

DESCRIPTION
The ds28e17iic driver provides a 1-Wire to I2C bridge with a iic(4) bus at the far end using the DS28E17 bridge chip.

The DS28E17 will automatically detect and deal with a device at the other end of the bus that uses I2C clock stretching.

SYSCTL VARIABLES
The following sysctl(3) variables are provided:

hw.ds28e17iic0.readycount

hw.ds28e17iic0.readydelay
    When the driver sends a transaction down the 1-Wire bus, these variables are how long to delay before reading the status on whether or not the conversion is done and the number of times to perform this read back. In general, these values should be as short as possible, but if there are too short, a EAGAIN timeout will occur when the end device is just taking a longer than expect amount of time to respond. This may be particularly noticed if end device is doing clock stretching.

hw.ds28e17iic0.reportreadnostop
    If set to 1, report that an attempt to do a Read without a Stop occurred. The chip does not support that operation. Read without Stop will be treated as a Read with a Stop with the hope that the end device will be able to deal with that.

hw.ds28e17iic0.reportzerolen
    If set to 1, report that an attempt to perform a zero length read or zero length write occurred. The chip does not support zero length reads or writes.

hw.ds28e17iic0.debug
    If the driver is compiled with DS28E17IIC_DEBUG, this node will appear and can be used to set the debugging level.

SEE ALSO
onewire(4), iic(4), sysctl(8)

HISTORY
The ds28e17iic driver first appeared in NetBSD 11.0.

AUTHORS
-nosplit The ds28e17iic driver was written by Brad Spencer <brad@anduin.eldar.org>.

BUGS
While this may not be considered a bug, the DS28E17 chip will detach itself from the onewire(4) bus if there is not a device connected to its SDA and SCL pins.

The i2cscan(8) command will not function entirely correctly when run against a DS28E17 chip. The default mode of doing a I2C Write with Stop that is zero length is not supported by the DS28E17 chip. When the i2cscan(8) command is used with its one byte read mode it will find devices as long as the device does not NACK on a I2C read.