GPS Module

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HW-595 Board

uBlox GPS 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

Software

U-Center

GPSD

Check data stream with gpsmon:

gpsmon /dev/ttyS0

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.

Pulse Per Second (PPS)

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

Check PPS signal:

ppstest /dev/pps0
ppscheck /dev/ttyS0