ASUS Tinker Board: リアルタイムクロックモジュール(RTC DS3231)を使う

概要

ラズパイで使ったことのある、RTCモジュール DS3231 を、ASUS TinkerBoardで使ってみる。

環境

• TinkerOS debian 2.0.1 beta

  linaro@linaro-alip:~$ uname -a
  Linux linaro-alip 4.4.71+ #1 SMP Thu Aug 17 00:28:01 CST 2017 armv7l GNU/Linux
  

• DS3231 module (I2C)

tl;dr

1. Kernel setting & Sync RTC

   # Switch to 'root'
   sudo -s
   # Get files
   wget https://raw.githubusercontent.com/mt08xx/files/master/TinkerBoard/kernel_module/lib/modules/4.4.71/kernel/drivers/rtc/rk3288-miniarm.dtb
   wget https://raw.githubusercontent.com/mt08xx/files/master/TinkerBoard/kernel_module/lib/modules/4.4.71/kernel/drivers/rtc/rtc-ds1307.ko
   # rk3288-miniarm.dtb : backup & copy
   [ ! -e /boot/rk3288-miniarm.dtb.org ] && mv -v /boot/rk3288-miniarm.dtb  /boot/rk3288-miniarm.dtb.org
   mv -v ./rk3288-miniarm.dtb  /boot/rk3288-miniarm.dtb 
   # rtc-ds1307.ko
   mkdir -p /lib/modules/4.4.71+/kernel/drivers/rtc/
   mv -v ./rtc-ds1307.ko /lib/modules/4.4.71+/kernel/drivers/rtc/
   #
   depmod -a
   # Reboot
   sync && sleep 5 && reboot
   # After reboot, you can see /dev/rtc1 .
   

   => /dev/rtc1 が現れる

2. ファイルを4つ編集 / Edit 4 files.

   • rtc0 => rtc1

     /etc/default/hwclock

     ...
     ...
     HCTOSYS_DEVICE=rtc1
     

     /lib/udev/rules.d/85-hwclock.rules

     KERNEL=="rtc1", RUN+="/lib/udev/hwclock-set $root/$name"
     

     /lib/udev/rules.d/50-udev-default.rules

     SUBSYSTEM=="rtc", KERNEL=="rtc1", SYMLINK+="rtc", OPTIONS+="link_priority=-100"
     

   • Comment out

     /lib/udev/hwclock-set

     #if [ -e /run/systemd/system ] ; then
     #    exit 0
     #fi
     

3. RTCモジュールの時刻同期 / Sync time for RTC module

   # Switch to 'root'
   sudo -s
   # Check Current RTC time.
   hwclock --rtc=/dev/rtc1 --get
   # Stop ntp service
   systemctl stop ntp
   # 
   ntpdate -v time.nist.gov 
   # Update RTC time : --systohc
   hwclock --rtc=/dev/rtc1 -w
   # Check Current RTC time again.
   hwclock --rtc=/dev/rtc1 --get
   #
   # Reboot
   reboot
   

ビルド / build

1. Prepare Build Environment ( cross / self ...they may need to be updated...)
2. git clone --depth 1 -b linux4.4-rk3288 https://github.com/TinkerBoard/debian_kernel.git

3. drivers/rtc/rtc-ds1307.ko

   drivers/rtc/rtc-ds1307.ko

   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- miniarm-rk3288_defconfig
   echo "CONFIG_RTC_DRV_DS1307=m" >> .config
   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- modules
   

4. arch/arm/boot/dts/rk3288-miniarm.dtb

   arch/arm/boot/dts/rk3288-miniarm.dts

   diff --git a/arch/arm/boot/dts/rk3288-miniarm.dts b/arch/arm/boot/dts/rk3288-miniarm.dts
   index cf11a15..85e80c4 100755
   --- a/arch/arm/boot/dts/rk3288-miniarm.dts
   +++ b/arch/arm/boot/dts/rk3288-miniarm.dts
   @@ -589,6 +589,10 @@
                   reg = <0x4c>;
                   status = "disabled";
           };
   +        rtc: ds1307@68 {
   +                compatible = "dallas,ds1307";
   +                reg = <0x68>;
   +        };
    };
    &i2c3 {
   

   arch/arm/boot/dts/rk3288-miniarm.dtb

   make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- dtbs