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authorHeiko Schocher <hs@denx.de>2008-10-15 09:39:47 +0200
committerWolfgang Denk <wd@denx.de>2008-10-18 21:54:02 +0200
commit67b23a322848d828a5e45c0567b72762bfde7abf (patch)
tree8dc26375504482eaa0e9600a6a52a6bb047dccf3 /README
parentc24853644ddd2dd2e4246b5854a93e6254a14092 (diff)
I2C: adding new "i2c bus" Command to the I2C Subsystem.
With this Command it is possible to add new I2C Busses, which are behind 1 .. n I2C Muxes. Details see README. Signed-off-by: Heiko Schocher <hs@denx.de>
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@@ -1429,6 +1429,53 @@ The following options need to be configured:
Define this option if you want to use Freescale's I2C driver in
drivers/i2c/fsl_i2c.c.
+ CONFIG_I2C_MUX
+
+ Define this option if you have I2C devices reached over 1 .. n
+ I2C Muxes like the pca9544a. This option addes a new I2C
+ Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
+ new I2C Bus to the existing I2C Busses. If you select the
+ new Bus with "i2c dev", u-bbot sends first the commandos for
+ the muxes to activate this new "bus".
+
+ CONFIG_I2C_MULTI_BUS must be also defined, to use this
+ feature!
+
+ Example:
+ Adding a new I2C Bus reached over 2 pca9544a muxes
+ The First mux with address 70 and channel 6
+ The Second mux with address 71 and channel 4
+
+ => i2c bus pca9544a:70:6:pca9544a:71:4
+
+ Use the "i2c bus" command without parameter, to get a list
+ of I2C Busses with muxes:
+
+ => i2c bus
+ Busses reached over muxes:
+ Bus ID: 2
+ reached over Mux(es):
+ pca9544a@70 ch: 4
+ Bus ID: 3
+ reached over Mux(es):
+ pca9544a@70 ch: 6
+ pca9544a@71 ch: 4
+ =>
+
+ If you now switch to the new I2C Bus 3 with "i2c dev 3"
+ u-boot sends First the Commando to the mux@70 to enable
+ channel 6, and then the Commando to the mux@71 to enable
+ the channel 4.
+
+ After that, you can use the "normal" i2c commands as
+ usual, to communicate with your I2C devices behind
+ the 2 muxes.
+
+ This option is actually implemented for the bitbanging
+ algorithm in common/soft_i2c.c and for the Hardware I2C
+ Bus on the MPC8260. But it should be not so difficult
+ to add this option to other architectures.
+
- SPI Support: CONFIG_SPI