GPS Module: Difference between revisions

Latest revision as of 19:47, 5 June 2024

HW-595 Board

Based on uBlox NEO-6M-0-001
Receiver Description
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
PPS LED: Invertion of PPS pin
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 (by default)
2	RXD	UART input
3	TXD	UART output
4	GND	Ground
5	VCC	3.3 - 5 V

PPS:

Send PPS to UART via CTS to allow GPSD to acurately sync
Can be configured as a frequency reference: 0.25 Hz - 10 MHz
- Output has high frequency accuracy
- Suffers from jitter except at a few specific frequencies
Configure in u-Center here
Different frquencies/duty cycles can be configure for GPS synced/not synced

Software

U-Center

U-Center
Select COM port and Baud rate
Communicates with uBlox with binary UBX Protocol

View -> Configuration View; to activate change: Send

CFG (Configuration)
- Select: Save current configuration
- Select in Devices: 2-I2C-EEPROM
PRT (Ports)
- Baud Rate : 9600 -> 115200
TP5 (Timepulse 5)
- PPS Settings for no GPS lock (eg use as an "alert" signal:
  - Frequency : 1 Hz -> 10 Hz
  - Duty Cycle : 100% -> 25% (alternatively set to 0% for permanent low output)
- PPS Settings for GPS Locked:
  - Frequency Locked : 1 Hz
  - Duty Locked : 50%
- Rising Edge on TOS
- Cable Delay : 50 ns -> 10 ns (This compensates for cable delay between antenna and receiver)

View -> Message View:

Firmware version: UBX -> MON (Monitor) -> VER (Version)
- Currently: 7.03 (45969)

GPSD

gpsd
Packages: gpsd, gpsd-clients

Use of a serial device (eg ttyS0) is prefered over a USB/serial interface (eg ttyUSB0) due to lower latency and PPS availability.

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, which by default enables detection of USB devices via udev events including creation of a PPS device (/dev/pps0):

USBAUTO="true"

Options can be forced, eg:

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

Check data stream with gpsmon:

gpsmon /dev/ttyS0

when gpsd is not started, or connected to gpsd:

gpsmon

Can show raw data:

gpscat /dev/ttyS0

Enable and start gpsd:

systemctl enable gpsd
systemctl start gpsd

Monitor with:

cgps -s
gpsmon
gpscsv
gpsplot --image gps.png
xgps

Pulse Per Second (PPS)

With PPS output connected to a serial port pin, GPSD should detect it. If it is on GPIO or other serial port, this can be used to create a PPS device:

dnf install pps-tools
modprobe pps_ldisc
setserial -v /dev/ttyS0 low_latency
ldattach PPS /dev/ttyS0

Check PPS signal:

ppstest /dev/pps0
ppscheck /dev/ttyS0

Can set at boot with udev rule (/etc/udev/rules.d/gps.rules):

KERNEL=="ttyS0", SYMLINK+="gps0"
KERNEL=="ttyS0", RUN+="/usr/bin/setserial -v /dev/%k low_latency"
KERNEL=="ttyS0", RUN+="/usr/sbin/ldattach PPS /dev/%k"

@@ Line 1: / Line 1: @@
 == HW-595 Board  ==
 [[Image:UBlox_GPS_Module.jpg|top|thumbnail|uBlox GPS Board]]
 * Based on [https://www.u-blox.com/en/product/neo-6-series uBlox NEO-6M-0-001]
+* [https://content.u-blox.com/sites/default/files/products/documents/u-blox6_ReceiverDescrProtSpec_%28GPS.G6-SW-10018%29_Public.pdf Receiver Description]
 * 5V operation (3.3 V regulator onboard)
 * UART: 4800 - 230400 bps (9600 bps 8N1 default), TTL levels buffered by 220R resistors
 * [https://en.wikipedia.org/wiki/Hirose_U.FL U.FL] connector supplies 3.3 V to active antenna
 * Crystal Osc, not TCXO
-* LED:
+* PPS LED: Invertion of PPS pin
-** Constant: Searching
-** Blink 1s: Position fix
 * Battery-backed RAM contains config data and clock and speeds first-time-to-fix
 * Data in [http://www.gpsinformation.org/dale/nmea.htm NMEA] 0183 format
@@ Line 24: / Line 23: @@
 |1
 |PPS
-|1 pulse/s, synchronised at rising edge, length 100 ms
+|1 pulse/s, synchronised at rising edge, length 100 ms (by default)
 |-
 |2
@@ Line 43: / Line 42: @@
 |}
-PPS can be reconfigured as a frequency reference:
+PPS:
-* Send PPS to UART via CTS
+* Send PPS to UART via CTS to allow GPSD to acurately sync
-* 0.25 Hz - 10 MHz
+* Can be configured as a frequency reference: 0.25 Hz - 10 MHz
+** Output has high frequency accuracy
+** Suffers from jitter except at a few specific frequencies
 * Configure in u-Center [[Media:u-Center Configuration.png|here]]
-* Output has high frequency accuracy, but suffers from jitter except at a few specific frequencies
+* Different frquencies/duty cycles can be configure for GPS synced/not synced
 == Software ==
@@ Line 54: / Line 55: @@
 * [https://www.u-blox.com/en/product/u-center U-Center]
+* Select COM port and Baud rate
+* Communicates with uBlox with binary UBX Protocol
+View -> Configuration View; to activate change: Send
+* CFG (Configuration)
+** Select: Save current configuration
+** Select in Devices: 2-I2C-EEPROM
+* PRT (Ports)
+** Baud Rate : 9600 -> 115200
+* TP5 (Timepulse 5)
+** PPS Settings for no GPS lock (eg use as an "alert" signal:
+*** Frequency : 1 Hz -> 10 Hz
+*** Duty Cycle : 100% -> 25% (alternatively set to 0% for permanent low output)
+** PPS Settings for GPS Locked:
+*** Frequency Locked : 1 Hz
+*** Duty Locked : 50%
+** Rising Edge on TOS
+** Cable Delay : 50 ns -> 10 ns (This compensates for cable delay between antenna and receiver)
+View -> Message View:
+* Firmware version: UBX -> MON (Monitor) -> VER (Version)
+** Currently: 7.03 (45969)
 === GPSD ===
@@ Line 60: / Line 83: @@
 * Packages: gpsd, gpsd-clients
-Check data stream with [https://gpsd.gitlab.io/gpsd/gpsmon.html gpsmon]:
+Use of a serial device (eg ttyS0) is prefered over a USB/serial interface (eg ttyUSB0) due to lower latency and [https://docs.kernel.org/driver-api/pps.html PPS] availability.
- 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
+Configuration in /etc/sysconfig/gpsd, which by default enables detection of USB devices via udev events including creation of a PPS device (/dev/pps0):
+ USBAUTO="true"
+Options can be forced, eg:
   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:
+Check data stream with [https://gpsd.gitlab.io/gpsd/gpsmon.html gpsmon]:
-  USBAUTO="true"
+ gpsmon /dev/ttyS0
+when gpsd is not started, or connected to gpsd:
+  gpsmon
 Can show raw data:
@@ Line 79: / Line 107: @@
   systemctl enable gpsd
   systemctl start gpsd
-With gpsd running and without arguments, gpsmon will connect to gpsd port:
- gpsd
 Monitor with:
   cgps -s
-Or
   gpsmon
   gpscsv
+ gpsplot --image gps.png
   xgps
 === Pulse Per Second (PPS) ===
+With PPS output connected to a serial port pin, GPSD should detect it. If it is on GPIO or other serial port, this can be used to create a PPS device:
   dnf install pps-tools