path: root/Documentation/w1
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authorMadhusudhan Chikkature <>2008-11-12 13:27:12 -0800
committerLinus Torvalds <>2008-11-12 17:17:18 -0800
commite0a29382c6f51c278a7e9a788917ff9182f3dba6 (patch)
tree9e342053be04badb7e404a7c8666d5255e7cb2ef /Documentation/w1
parentcfbc619033d3a2eee8f7aa9314e21b96cf34d399 (diff)
hdq: documentation for OMAP HDQ
Add a brief document about omap2430/3430 HDQ/1-wire driver. Signed-off-by: Madhusudhan Chikkature<> Acked-by: Evgeniy Polyakov <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
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+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:
+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.
+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
+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.
+insmod omap_hdq.ko W1_ID=2
+inamod w1_bq27000.ko F_ID=2