GPS Module

HW-595 Board

Based on uBlox NEO-6M-0-001
5V operation (3.3 V regulator onboard)
UART: 4800 - 230400 bps (9600 bps 8N1 default), TTL levels buffered by 220R resistors
U.FL connector supplies 3.3 V to active antenna
Crystal Osc, not TCXO
LED:
- Constant: Searching
- Blink 1s: Position fix
Battery-backed RAM contains config data and clock and speeds first-time-to-fix
Data in NMEA 0183 format
More background here

Board pinouts:

Pin	Function	Description
1	PPS	1 pulse/s, synchronised at rising edge, length 100 ms
2	RXD	UART input
3	TXD	UART output
4	GND	Ground
5	VCC	3.3 - 5 V

PPS can be reconfigured as a frequency reference:

Send PPS to UART via CTS
0.25 Hz - 10 MHz
Configure in u-Center here
Output has high frequency accuracy, but suffers from jitter except at a few specific frequencies

Can be tested with something like (Debug level 4) :

gpsd -N -n -s 9600 -D 4 /dev/ttyS0 /dev/pps0

Configuration in /etc/sysconfig/gpsd

OPTIONS="-n -s 9600"
DEVICES="/dev/ttyS0 /dev/pps0"

Should auto-detect which UART is GPS connected to (baud rate, etc, with no configuration) with:

USBAUTO="true"

Enable and start gpsd:

systemctl enable gpsd
systemctl start gpsd

Use gpsmon to monitor GPS data, or xgps.

dnf install pps-tools
modprobe pps_ldisc
ldattach 18 /dev/ttyS0

Check PPS signal:

ppstest /dev/pps0
ppscheck /dev/ttyS0