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

    ```bash
# 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

1. ファイルを4つ編集 / Edit 4 files.

   • rtc0 => rtc1

     /etc/default/hwclock

...
...
HCTOSYS_DEVICE=rtc1

        ```bash:/lib/udev/rules.d/85-hwclock.rules
KERNEL=="rtc1", RUN+="/lib/udev/hwclock-set $root/$name"

    ```bash:/lib/udev/rules.d/50-udev-default.rules

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

    - Comment out

        ```bash:/lib/udev/hwclock-set
# if [ -e /run/systemd/system ] ; then
#    exit 0
# fi

1. 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](http://qiita.com/mt08/items/e8afe6de9e8a0bf1e89f) / [self](http://qiita.com/mt08/items/890a71d0b399ac1a9b49) ...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`

    ```bash: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

1. 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