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--- en:xu3_hardware_i2c [2017/06/14 16:04]
ruppi [How to change the I2C clock speed]
+++ en:xu3_hardware_i2c [2017/07/07 11:29] (current)
john1117 [How to change the I2C clock speed]
@@ Line 101: / Line 101: @@
 Make a backup of DTB file.
+  * kernel 4.9.y
 <code>
-cp /media/boot/meson64_odroidc2.dtb /media/boot/exynos5422-odroidxu3.dtb.org
+cp /media/boot/exynos5422-odroidxu4.dtb /media/boot/exynos5422-odroidxu4.dtb.org
+</code>
+  * kernel 3.10.y
+<code>
+cp /media/boot/exynos5422-odroidxu3.dtb /media/boot/exynos5422-odroidxu3.dtb.org
 </code>
-Change the DTB file for i2c-1 (i2c channel #1)
+Using dtc command, you can make "dts" type of device tree from "dtb" type.
+  * kernel 4.9.y
+<code>
+dtc -I dtb -O dts -o exynos5422-odroidxu4.dts exynos5422-odroidxu4.dtb
+</code>
+  * kernel 3.10.y
+<code>
+dtc -I dtb -O dts -o exynos5422-odroidxu3.dts exynos5422-odroidxu3.dtb
+</code>
-Find the i2c@12c70000 section in the dts file
+And, open by an editor you like it and check the i2c path.
 <code>
-fdtput -t i /media/boot/exynos5422-odroidxu3.dtb /i2c@12c70000 samsung,i2c-max-bus-freq "100000"
+vi exynos5422-odroidxu4.dts
+--------------------------------------
+..
+/ {
+..
+    soc {
+..
+    i2c@12C70000 {
+..
+--------------------------------------
+</code>
+Check current maximum bus frequency of i2c@12C70000
+  * kernel 4.9.y
+<code>
+fdtget /media/boot/exynos5422-odroidxu4.dtb /soc/i2c@12C70000 samsung,i2c-max-bus-freq
+</code>
+  * kernel 3.10.y
+<code>
+fdtget /media/boot/exynos5422-odroidxu3.dtb /i2c@12C70000 samsung,i2c-max-bus-freq
+</code>
+Change the DTB file for i2c-1 (i2c channel #1)
+  * kernel 4.9.y
+<code>
+fdtput -t i /media/boot/exynos5422-odroidxu4.dtb /soc/i2c@12C70000 samsung,i2c-max-bus-freq "10000"
+sync
+reboot
+</code>
+  * kernel 3.10.y
+<code>
+fdtput -t i /media/boot/exynos5422-odroidxu3.dtb /i2c@12C70000 samsung,i2c-max-bus-freq "10000"
 sync
 reboot
 </code>
 If you want to go back to original 400Khz mode, change "10000" to "400000".\\
 **Actual I2C clock speed** (Measured with an oscilloscope)\\
-In 400Khz mode : 370Khz \\
+In 400Khz mode : 344.8khz \\
-In 10Khz mode : 10Khz \\
+In 100Khz mode : 63.7khz \\
+In 10Khz mode : 9.3Khz \\
 **Default I2C clock speed** \\