GPS data is collected well, but pps data is not collected

Question

I have a Raspberry Pi 3 B+ with Raspberrypi add-on GPS module based NEO-6. I configured the device to act as NTP server but the NTP server won't work. When I use ppstest command, I get the following error:

trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)
time_pps_fetch() error -1 (Connection timed out)

GPS data is well received. Below are the things I set up. Should I add something else? did i do something wrong?

/boot/cmdline.txt is as follow:

dwc_otg.lpm_enable=0 console=ttyUSB0 root=PARTUUID=3d93e7aa-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles consoleblank=0

/boot/config.txt I added the following lines:

core_freq=250
enable_uart=1
dtoverlay=pi3-mini uart-bt
force_turbo=1
dtparam=spi=on
dtoverlay=pps-gpio,gpiopin=24

/etc/default/gpsd is as follow:

    # Default settings for the gpsd init script and the hotplug wrapper.

# Start the gpsd daemon automatically at boot time
START_DAEMON="true"

# Use USB hotplugging to add new USB devices automatically to the daemon
USBAUTO="true"

# Devices gpsd should collect to at boot time.
# They need to be read/writeable, either by user gpsd or the group dialout.
DEVICES="/dev/ttyUSB0 /dev/pps0"

# Other options you want to pass to gpsd
GPSD_OPTIONS="-n"

/etc/modules is as follow:

# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

i2c-dev
pps-gpio

dmesg | grep pps show as follow:

[    6.084130] pps_core: LinuxPPS API ver. 1 registered
[    6.084151] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <[email protected]>
[    6.102845] pps pps0: new PPS source [email protected]
[    6.102981] pps pps0: Registered IRQ 200 as PPS source
[   16.096467] pps_ldisc: PPS line discipline registered
[   16.100201] pps pps1: new PPS source usbserial0
[   16.100267] pps pps1: source "/dev/ttyUSB0" added

Thanks.

Answer 1

PPS devices provide accurate second alignmemt, but the second naming has to come from another source, normally NEMA or binary data from the receiver.

So the first thing to check is whether NTP is accepting the GPS source over the serial port.

Assuming it is, then the PPS diags suggest either the PPS signal isn't getting to the board, or it is coming in on the wrong pin.

Most of the neo6 boards I see online don't have a PPS line at all. Have you checked it does actually have PPS in addition to the serial Tx and Rx? If so, is it definitely going to gpio24?