2008-11-13 04:27:12 +07:00
|
|
|
Kernel driver for omap HDQ/1-wire module.
|
|
|
|
|
========================================
|
|
|
|
|
|
|
|
|
|
Supported chips:
|
|
|
|
|
================
|
|
|
|
|
HDQ/1-wire controller on the TI OMAP 2430/3430 platforms.
|
|
|
|
|
|
|
|
|
|
A useful link about HDQ basics:
|
|
|
|
|
===============================
|
2010-07-24 10:51:24 +07:00
|
|
|
http://focus.ti.com/lit/an/slua408a/slua408a.pdf
|
2008-11-13 04:27:12 +07:00
|
|
|
|
|
|
|
|
Description:
|
|
|
|
|
============
|
|
|
|
|
The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware
|
|
|
|
|
protocol of the master functions of the Benchmark HDQ and the Dallas
|
|
|
|
|
Semiconductor 1-Wire protocols. These protocols use a single wire for
|
|
|
|
|
communication between the master (HDQ/1-Wire controller) and the slave
|
|
|
|
|
(HDQ/1-Wire external compliant device).
|
|
|
|
|
|
|
|
|
|
A typical application of the HDQ/1-Wire module is the communication with battery
|
|
|
|
|
monitor (gas gauge) integrated circuits.
|
|
|
|
|
|
|
|
|
|
The controller supports operation in both HDQ and 1-wire mode. The essential
|
|
|
|
|
difference between the HDQ and 1-wire mode is how the slave device responds to
|
|
|
|
|
initialization pulse.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 as it does in the 1-Wire protocol.
|
|
|
|
|
|
|
|
|
|
Remarks:
|
|
|
|
|
========
|
|
|
|
|
The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the
|
|
|
|
|
controller. In this mode, as we can not read the ID which obeys the W1
|
|
|
|
|
spec(family:id:crc), a module parameter can be passed to the driver which will
|
|
|
|
|
be used to calculate the CRC and pass back an appropriate slave ID to the W1
|
|
|
|
|
core.
|
|
|
|
|
|
|
|
|
|
By default the master driver and the BQ slave i/f
|
|
|
|
|
driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1.
|
|
|
|
|
Please note to load both the modules with a different ID if required, but note
|
|
|
|
|
that the ID used should be same for both master and slave driver loading.
|
|
|
|
|
|
|
|
|
|
e.g:
|
|
|
|
|
insmod omap_hdq.ko W1_ID=2
|
|
|
|
|
inamod w1_bq27000.ko F_ID=2
|
|
|
|
|
|
2015-09-15 00:54:33 +07:00
|
|
|
The driver also supports 1-wire mode. In this mode, there is no need to
|
|
|
|
|
pass slave ID as parameter. The driver will auto-detect slaves connected
|
|
|
|
|
to the bus using SEARCH_ROM procedure. 1-wire mode can be selected by
|
|
|
|
|
setting "ti,mode" property to "1w" in DT (see
|
|
|
|
|
Documentation/devicetree/bindings/w1/omap-hdq.txt for more details).
|
|
|
|
|
By default driver is in HDQ mode.
|
