Show pageOld revisionsBacklinksBack to top This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong. ====== Enable PPS support in Raspian ====== DUNE has a task called ''%%Supervisors.ClockPPS%%'' that is used to dicipline the clock from both ''%%IMC::GpsFix%%'' messages and a PPS source. To get this to work, the kernel has to be compiled with two options not currently enabled by default: * CONFIG_PPS ("PPS support" in "make menuconfig") * CONFIG_NTP_PPS ("PPS kernel consumer support" in "make menuconfig") ==== Install dependencies ==== ''%%sudo apt install git bc bison flex libssl-dev%%'' ==== Download kernel ==== mkdir ppskernel cd ppskernel git clone https://github.com/raspberrypi/linux.git cd linux make mrproper zcat /proc/config.gz > .config make oldconfig ==== Configure kernel build options ==== Then comes the hard part, setting the options. Normally this is straight forward, but due to some options only showing when others are disabled, it may be a little tricky. * Run ''%%make menuconfig%%'' * Go to ''%%General setup ---> Timers subsystem --->%%'' and disable ''%%Old Idle dynticks config%%'', then enter ''%%Timer tick handling%%'' and change it to ''%%Periodic timer ticks (constant rate, no dynticks)%%'' * Turn on PPS support: ''%%PPS kernel consumer support %%'' is the option that should have become visible after changing the timer settings. If not, save and reload ''%%make menuconfig%%''. * Enter Device Drivers ---> PPS support ---> \\ <M> PPS support [ ] PPS debugging messages [*] PPS kernel consumer support *** PPS clients support *** < > Kernel timer client (Testing client, use for debug) <M> PPS line discipline <M> PPS client using GPIO *** PPS generators support *** \\ * Save and exit. To verify, check the ''%%.config%%'' file that has been created in the same folder (nano .config). These options should be present somewhere in the file: \\ CONFIG_PPS=y CONFIG_NTP_PPS=y # # Timers subsystem # CONFIG_TICK_ONESHOT=y CONFIG_HZ_PERIODIC=y # CONFIG_NO_HZ_IDLE is not set # CONFIG_NO_HZ_FULL is not set # CONFIG_NO_HZ is not set CONFIG_HIGH_RES_TIMERS=y # CONFIG_PREEMPT_NONE is not set CONFIG_PREEMPT_VOLUNTARY=y # CONFIG_PREEMPT is not set ==== Compile the kernel ==== make -j4 make modules \\ * Gain superuser privileges and transfer a copy of the new kernel to the boot partition: \\ sudo -i cd ~pi/ppskernel/linux-rpi-[kernel version number].y make modules_install cp ./arch/arm/boot/zImage /boot/kernel_new.img \\ * Tell the system to use this new kernel by adding ''%%kernel=kernel_new.img%%'' to ''%%/boot/config.txt %%''. * Reboot ==== Add PPS source and load kernel module ==== * Open ''%%/boot/config.txt %%'' again, and ''%%dtoverlay=pps-gpio,gpiopin=[GPIOPIN]%%'' where GPIOPIN is the PPS signal. * Load kernel module: ''%%sudo modprobe pps-gpio%%'' ==== Test and make permanent==== * Test \\ apt-get install pps-tools sudo ppstest /dev/pps0 \\ * Expected result is something like: \\ trying PPS source "/dev/pps0" found PPS source "/dev/pps0" ok, found 1 source(s), now start fetching data... source 0 - assert 1572772437.999997402, sequence: 6168 - clear 0.000000000, sequence: 0 source 0 - assert 1572772438.999997803, sequence: 6169 - clear 0.000000000, sequence: 0 source 0 - assert 1572772440.000000924, sequence: 6170 - clear 0.000000000, sequence: 0 source 0 - assert 1572772440.999998834, sequence: 6171 - clear 0.000000000, sequence: 0 source 0 - assert 1572772442.000001424, sequence: 6172 - clear 0.000000000, sequence: 0 source 0 - assert 1572772442.999999478, sequence: 6173 - clear 0.000000000, sequence: 0 source 0 - assert 1572772444.000000128, sequence: 6174 - clear 0.000000000, sequence: 0 source 0 - assert 1572772444.999999537, sequence: 6175 - clear 0.000000000, sequence: 0 source 0 - assert 1572772446.000000578, sequence: 6176 - clear 0.000000000, sequence: 0 \\ * If successful, make permanent by opening ''%%/etc/modules%%'' and adding ''%%pps-gpio%%'' to the end. * Running a DUNE configuration with ''%%Supervisors.ClockPPS%%'' should now work ===== Links ===== * [[https://support.ntp.org/bin/view/Sandbox/HowtoPpsOnRaspberryPi|How to PPS on Raspberry Pi]] * [[https://ava.upuaut.net/?p=951|5 minute guide to making a GPS Locked Stratum 1 NTP Server with a Raspberry Pi]] * [[http://brandon.penglase.net/index.php?title=NavSpark_GPS%2BGLONASS_Stratum-1_NTP_Time_Source_with_a_Raspberry_Pi#Configure_the_kernel|NavSpark GPS+GLONASS Stratum-1 NTP Time Source with a Raspberry Pi]] * [[https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html|The Raspberry Pi as a Stratum-1 NTP Server]] enable_pps_support_raspian.txt Last modified: 2019/11/03 09:25by nikolal