RE: HDQ/1-wire module

["Madhusudhan Chikkature Rajashekar" <madhu.cr@ti.com>]

Hi All,

In response to the below mail on supporting the HDQ/1-wire module, I had further discussions with the W1 maintainer Evgeniy Polyakov
on this.
I intend to submit an RFC/PATCH to linux omap list for supporting the HDQ/1-wire controller on OMAP243x/34xx platforms. The
RFC/PATCH will include a master driver for the HDQ/1-wire controller and a slave driver interface to support the BQ27000 hdq
complaint gas guage device. The actual BQ battery driver can then be developed based on this.
 
Thanks,
Madhu
 

-----Original Message-----
From: Madhusudhan Chikkature Rajashekar [mailto:madhu.cr@ti.com] 
Sent: Wednesday, November 07, 2007 2:12 PM
To: 'linux-omap-open-source@linux.omap.com'
Subject: HDQ/1-wire module

Hi All,

This is regarding the HDQ/1-wire support for omap24xx/34xx. 

The controller on the above OMAP platforms supports both HDQ and 1-wire protocol.The difference between HDQ and 1-wire protocol is
very minimal as explained below.

HDQ Mode:
In HDQ mode, the firmware does not require the host to create an initialization pulse to the slave.
However, the slave can be reset by using an initialization pulse (also referred to as a break pulse).
The slave does not respond with a presence pulse.

1-Wire Mode:
In 1-Wire protocol, the host first sends an initialization pulse (by pulling the line to a logic-low state)
and then waits for the slave to respond with a presence pulse before enabling any communication sequence.

A typical application of the HDQ/1-Wire module is the communication with battery monitor (gas gauge)
integrated circuits.

Has anyone in the past worked on the above module or has written a driver for the same? I can not recollect of having read any mails
on the above module
in the list. Please correct me if I am wrong.

There is no support for HDQ devices as of today in Linux. Whereas there is a W1 subsystem for 1-wire devices. Right now, I only have
a device 
that is complaint to HDQ protocol only.I guess we can still write a driver to support this which can be integrated to the 1-wire
subsystem. If anyone has a different opinion, please do share the views.

Regards,
Madhu