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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 [2017/06/20 16:05] neal [How to change the I2C clock speed] |
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Make a backup of DTB file. | Make a backup of DTB file. | ||
+ | * kernel 4.9.y | ||
<code> | <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> | </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> | <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 | sync | ||
reboot | reboot | ||
</code> | </code> | ||
- | |||
If you want to go back to original 400Khz mode, change "10000" to "400000".\\ | If you want to go back to original 400Khz mode, change "10000" to "400000".\\ | ||
**Actual I2C clock speed** (Measured with an oscilloscope)\\ | **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** \\ | **Default I2C clock speed** \\ |