前言 最近入坑了无限垫，玩 ft8 这类数字无线电需要比较精确的时间，就想到搞个 GPS 授时服务器，于是就开始折腾，一开始选择树莓派 zero 2w 作为主机，结果发现开发板只有1个 uart 接口，后来翻找手头的开发板发现辛狐的 pico 系列有多个 uart 接口，并且官方有很好的支持，修改起来比较简单就选用作为主机，最后成本还不超过100元。
硬件及接线方式 这里选用的 Luckfox Pico Plus ，可选用幸狐的其他开发板，设置根据开发板不同设置会有所不同，系统使用的是 buildroot ，GPS模块选用的是 ATGM336H
这里引用官网的引脚图
开发板 GPS模块
PIN36
VCC
PIN8
GND
PIN7
RX
PIN6
TX
PIN9
PPS
搭建编译环境和获取Luckfox SDK 使用系统为 Ubuntu 22.04.5
1 2 3 sudo apt updatesudo apt-get install -y git ssh make gcc gcc-multilib g++-multilib module-assistant expect g++ gawk texinfo libssl-dev bison flex fakeroot cmake unzip gperf autoconf device-tree-compiler libncurses5-dev pkg-config bc python-is-python3 passwd openssl openssh-server openssh-client vim file cpio rsync
1 2 3 4 5 # 国外网络 git clone https://github.com/LuckfoxTECH/luckfox-pico.git # 国内网络 git clone https://gitee.com/LuckfoxTECH/luckfox-pico.git
具体编译方式可以参考官方wiki，本文只介绍需要修改的步骤
修改设备树 虽然官方的luckfox-config工具能打开UART 4接口，但经过测试gpsd启动顺序比开启UART 4要早，导致gpsd无法识别模块，系统启动后需要手动重启服务，所以这里通过修改设备树开启UART 4接口
Luckfox Pico Plus 设备树文件位置sysdrv/source/kernel/arch/arm/boot/dts/rv1103g-luckfox-pico-plus.dts
首先需要再设备树根节点添加
1 2 3 4 5 6 pps { compatible = "pps-gpio"; pinctrl-names = "default"; gpios = <&gpio1 RK_PD2 GPIO_ACTIVE_HIGH>; status = "okay"; };
添加GPIO的部分
1 2 3 4 5 6 7 8 /**********GPIO**********/ &pinctrl { gpio1-pd2 { gpio1_pd2:gpio1-pd2 { rockchip,pins = <2 RK_PD2 RK_FUNC_GPIO &pcfg_pull_none>; }; }; };
这里使用UART 4接口，找到&uart4部分修改成以下
1 2 3 4 5 &uart4 { status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&uart4m1_xfer>; };
完整设备树文件
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 // SPDX-License-Identifier: (GPL-2.0+ OR MIT) /* * Copyright (c) 2022 Rockchip Electronics Co., Ltd. */ /dts-v1/; #include "rv1103.dtsi" #include "rv1106-evb.dtsi" #include "rv1103-luckfox-pico-ipc.dtsi" / { model = "Luckfox Pico Plus"; compatible = "rockchip,rv1103g-38x38-ipc-v10", "rockchip,rv1103"; pps { compatible = "pps-gpio"; pinctrl-names = "default"; gpios = <&gpio1 RK_PD2 GPIO_ACTIVE_HIGH>; status = "okay"; }; }; /**********GPIO**********/ &pinctrl { gpio1-pd2 { gpio1_pd2:gpio1-pd2 { rockchip,pins = <2 RK_PD2 RK_FUNC_GPIO &pcfg_pull_none>; }; }; }; /**********SFC**********/ &sfc { status = "okay"; flash@0 { compatible = "spi-nand"; reg = <0>; spi-max-frequency = <75000000>; spi-rx-bus-width = <4>; spi-tx-bus-width = <1>; }; }; /**********SDMMC**********/ &sdmmc { max-frequency = <50000000>; no-sdio; no-mmc; bus-width = <4>; cap-mmc-highspeed; cap-sd-highspeed; disable-wp; pinctrl-names = "default"; pinctrl-0 = <&sdmmc0_clk &sdmmc0_cmd &sdmmc0_det &sdmmc0_bus4>; status = "okay"; }; /**********ETH**********/ &gmac { status = "okay"; }; /**********USB**********/ &usbdrd_dwc3 { status = "okay"; dr_mode = "peripheral"; }; /**********SPI**********/ /* SPI0_M0 */ &spi0 { status = "disabled"; spidev@0 { spi-max-frequency = <50000000>; }; fbtft@0 { spi-max-frequency = <50000000>; }; }; /**********I2C**********/ /* I2C3_M1 */ &i2c3 { status = "disabled"; clock-frequency = <100000>; }; /* I2C0_M2 */ &i2c0 { status = "disabled"; clock-frequency = <100000>; }; /**********UART**********/ /* UART3_M1 */ &uart3 { status = "disabled"; }; /* UART4_M1 */ &uart4 { status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&uart4m1_xfer>; }; /**********PWM**********/ /* PWM1_M0 */ &pwm1 { status = "disabled"; };
内核设置 开启以下选项
1 2 3 Device Drivers ---> <*> PPS support ---> <*> PPS client using GPIO
Buildroot 设置 开启和关闭以下选项，这里使用chrony代替ntp，就关闭掉ntp，gpsd里选项NMEA2000和Navcom为NMEA协议可选可不选，本文并未使用该协议
1 2 3 4 5 6 7 8 9 10 Target packages ---> Hardware handling ---> [*] gpsd ---> -*- Navcom [*] NMEA2000 [*] minicom [*] pps-tools Networking applications ---> [*] chrony [ ] ntp
编译 根据官方的wiki的编译部分编译就行了
进入系统设置 通过ssh或者adb进入系统
修改gpsd启动脚本/etc/init.d/S50gpsd
DEVICES选项修改为/dev/ttyS4 /dev/pps0，这里设置gps模块连接开发板的uart和pps接口的位置启动命令需添加-n开启 PPS 的支持，若模块的波特率不是9600者需要添加-s <模块的波特率>，最后启动命令为start-stop-daemon -S -q -p $PIDFILE --exec $DAEMON -- -P $PIDFILE $DEVICES -s <模块的波特率> -n && echo "OK" || echo "Failed"
完整启动脚本
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 #!/bin/sh # # Starts the gps daemon. # NAME=gpsd DAEMON=/usr/sbin/$NAME DEVICES="/dev/ttyS4 /dev/pps0" PIDFILE=/var/run/$NAME.pid start() { printf "Starting $NAME: " start-stop-daemon -S -q -p $PIDFILE --exec $DAEMON -- -P $PIDFILE $DEVICES -s 115200 -n && echo "OK" || echo "Failed" } stop() { printf "Stopping $NAME: " start-stop-daemon -K -q -p $PIDFILE && echo "OK" || echo "Failed" rm -f $PIDFILE } restart() { stop start } case "$1" in start) start ;; stop) stop ;; restart|reload) restart ;; *) echo "Usage: $0 {start|stop|restart}" exit 1 esac exit $?
添加Chrony配置文件/etc/chrony.conf 这里的配置文件关闭了网络ntp获取时间，需要则把server前面的#去掉，并改为需要使用的ntp服务器
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 # Use public servers from the pool.ntp.org project. # Please consider joining the pool (http://www.pool.ntp.org/join.html). # NTP服务器地址。server可以配置多个 #server ntp.aliyun.com iburst #server ntp1.aliyun.com iburst #server time1.cloud.tencent.com iburst #server cn.ntp.org.cn iburst #server ntp.ntsc.ac.cn iburst # Record the rate at which the system clock gains/losses time. driftfile /var/lib/chrony/drift # Allow the system clock to be stepped in the first three updates # if its offset is larger than 1 second. makestep 1.0 3 # Enable kernel synchronization of the real-time clock (RTC). rtcsync # Enable hardware timestamping on all interfaces that support it. #hwtimestamp * # Increase the minimum number of selectable sources required to adjust # the system clock. #minsources 2 # Allow NTP client access from local network. # 允许连接到此服务器同步时间的网段；0.0.0.0/0表示允许所有网段；注释该配置此服务就只能作为NTP客户端，不能作为服务器 allow 0.0.0.0/0 # Serve time even if not synchronized to a time source. # 当配置的server不可用时，是否使用本地时间同步到客户端 local stratum 10 # Specify file containing keys for NTP authentication. #keyfile /etc/chrony.keys # Get TAI-UTC offset and leap seconds from the system tz database. #leapsectz right/UTC # Specify directory for log files. logdir /var/log/chrony # Select which information is logged. #log measurements statistics tracking #和服务器相差多少秒内才执行同步。本地时间和服务器时间相差的秒数超过这个时间就不会同步。默认是3秒 maxdistance 94608000.0 # GPS 接口配置 # SHM refclock is shared memory driver, it is populated by GPSd and read by chrony # it is SHM 0 # refid is what we want to call this source = NMEA # offset = 0.000 means we do not yet know the delay # precision is how precise this is. not 1e-3 = 1 millisecond, so not very precision # poll 0 means poll every 2^0 seconds = 1 second poll interval # filter 3 means take the average/median (forget which) of the 3 most recent readings. NMEA can be jumpy so we're averaging here refclock SHM 0 refid NMEA offset 0.000 precision 1e-3 poll 0 filter 3 # PPS 接口配置 # PPS refclock is PPS specific, with /dev/pps0 being the source # refid PPS means call it the PPS source # lock NMEA means this PPS source will also lock to the NMEA source for time of day info # offset = 0.0 means no offset... this should probably always remain 0 # poll 3 = poll every 2^3=8 seconds. polling more frequently isn't necessarily better # trust means we trust this time. the NMEA will be kicked out as false ticker eventually, so we need to trust the combo refclock PPS /dev/pps0 refid PPS lock NMEA offset 0.0 poll 3 trust
以上配置完成后可以重启系统，也可以重启服务/etc/init.d/S50gpsd和/etc/init.d/S49chrony
测试命令 测试 GPS 模块 使用minicom -D /dev/ttyS4检查 GPS 模块是否有输出，没有则检查模块接口是否连接正确
可用gpsmon或者cgps观察 gpsd 是否配置正确
测试 PPS 输出 使用pps /dev/pps0查看 PPS 接口是否有输出，一般在gps模块没有获取到信号或者没正确接线都会输出time_pps_fetch() error -1 (Connection timed out)，正常则输出source 0 - assert 1741791874.907876850, sequence: 6520 - clear 0.000000000, sequence: 0
Chrony 检查 GPS 和 PPS 授时状态 使用chronyc sourcestats检查授时状态
1 2 3 4 Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev ============================================================================== NMEA 15 8 14 -366.405 1426.521 +98ms 5653us PPS 15 8 191 +0.008 0.133 +13ns 3178ns
手动同步时间chronyc -a makestep
其他设置 固定有线网卡 Mac 地址 在网卡配置文件/etc/network/interfaces添加
1 2 3 auto eth0 iface eth0 inet dhcp hwaddress ether 1a:cf:50:33:5f:92
参考链接
