aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorMadhusudhan Chikkature <madhu.cr@ti.com>2008-11-12 16:27:12 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-12 20:17:18 -0500
commite0a29382c6f51c278a7e9a788917ff9182f3dba6 (patch)
tree9e342053be04badb7e404a7c8666d5255e7cb2ef
parentcfbc619033d3a2eee8f7aa9314e21b96cf34d399 (diff)
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>
-rw-r--r--Documentation/w1/masters/omap-hdq46
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 000000000000..ca722e09b6a1
--- /dev/null
+++ b/Documentation/w1/masters/omap-hdq
@@ -0,0 +1,46 @@
1Kernel driver for omap HDQ/1-wire module.
2========================================
3
4Supported chips:
5================
6 HDQ/1-wire controller on the TI OMAP 2430/3430 platforms.
7
8A useful link about HDQ basics:
9===============================
10http://focus.ti.com/lit/an/slua408/slua408.pdf
11
12Description:
13============
14The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware
15protocol of the master functions of the Benchmark HDQ and the Dallas
16Semiconductor 1-Wire protocols. These protocols use a single wire for
17communication between the master (HDQ/1-Wire controller) and the slave
18(HDQ/1-Wire external compliant device).
19
20A typical application of the HDQ/1-Wire module is the communication with battery
21monitor (gas gauge) integrated circuits.
22
23The controller supports operation in both HDQ and 1-wire mode. The essential
24difference between the HDQ and 1-wire mode is how the slave device responds to
25initialization pulse.In HDQ mode, the firmware does not require the host to
26create an initialization pulse to the slave.However, the slave can be reset by
27using an initialization pulse (also referred to as a break pulse).The slave
28does not respond with a presence pulse as it does in the 1-Wire protocol.
29
30Remarks:
31========
32The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the
33controller. In this mode, as we can not read the ID which obeys the W1
34spec(family:id:crc), a module parameter can be passed to the driver which will
35be used to calculate the CRC and pass back an appropriate slave ID to the W1
36core.
37
38By default the master driver and the BQ slave i/f
39driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1.
40Please note to load both the modules with a different ID if required, but note
41that the ID used should be same for both master and slave driver loading.
42
43e.g:
44insmod omap_hdq.ko W1_ID=2
45inamod w1_bq27000.ko F_ID=2
46