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author | Madhusudhan Chikkature <madhu.cr@ti.com> | 2008-11-12 13:27:12 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-11-12 17:17:18 -0800 |
commit | e0a29382c6f51c278a7e9a788917ff9182f3dba6 (patch) | |
tree | 9e342053be04badb7e404a7c8666d5255e7cb2ef /Documentation/w1 | |
parent | cfbc619033d3a2eee8f7aa9314e21b96cf34d399 (diff) | |
download | op-kernel-dev-e0a29382c6f51c278a7e9a788917ff9182f3dba6.zip op-kernel-dev-e0a29382c6f51c278a7e9a788917ff9182f3dba6.tar.gz |
hdq: documentation for OMAP HDQ
Add a brief document about omap2430/3430 HDQ/1-wire driver.
Signed-off-by: Madhusudhan Chikkature<madhu.cr@ti.com>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/w1')
-rw-r--r-- | Documentation/w1/masters/omap-hdq | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/w1/masters/omap-hdq b/Documentation/w1/masters/omap-hdq new file mode 100644 index 0000000..ca722e0 --- /dev/null +++ b/Documentation/w1/masters/omap-hdq @@ -0,0 +1,46 @@ +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: +=============================== +http://focus.ti.com/lit/an/slua408/slua408.pdf + +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 + |