Trimble Palisade Receiver

Synopsis

Description

This documentation describes version V2.43 (May 11, 1999) of the source.

Driver code for the Palisade receiver is being maintained by:
Sven Dietrich
Trimble Navigation Ltd.
645 North Mary Ave.
Sunnyvale, CA 94088-3642
 

Introduction

The following information should answer most questions regarding driver installation, deployment and debugging.

Receiver

Palisade generates a PPS synchronized to UTC within +/- 100 ns.  This level of precision is achieved using an over-determined time solution, a 40 ns pulse steering resolution and a T-RAIM (Time-Receiver Autonomous Integrity Monitor) algorithm. An external event input with 40 nanosecond resolution, is available for asynchronous time transfer applications.

Palisade self-surveys at power-up using TRAIM. No initialization of the receiver is required by the driver. It is recommended that Palisade be allowed to complete self-survey before starting NTP.
 

Compatibility

If you are compiling NTP from a software distribution, you can obtain latest software source, documentation, and compatibility information from:

    ftp://ftp.trimble.com/pub/ntp

A proprietary port of NTP for Windows NT is also posted on the above ftp site.
Windows NT support is available from Trimble on a no-support, beta-evaluation basis only.

This driver is compatible with the following versions of Palisade:
 

Version	External Event	Trimble Part Number
7.02	No	26664-00
7.02E	Yes	26664-10
7.12	Yes	38158-00

Note: If you are using Palisade 26664-00, you must set fudge flag2 to 1 in your ntp.conf file. See the configuration section below.
 

Installation

A location with unobstructed view of the horizon is recommended. Palisade is designed to be securely mounted atop standard 3/4 inch threaded pipe.

The 12 conductor (dia. 10 mm)  power and I/O cable must be routed from the rooftop site to the NTP server.

Connection

The following connections are required when connecting Palisade with a host:
 

Description	Host				Palisade
Port A	DB-9	DB-25		RS-232	RS-422	Palisade Pinout
Receive Data	2	3	<--	Green	Green / Blue	8 (T-) & 10 (T+)
Transmit Data	3	2	<--	N/C	N/C
Request to Send	7	4	<--	Gray	Gray / White	6 (R-) & 7 (R+)
Signal Ground	5	7	<--	Black	Black	9 (GND)
Port B
Receive Data	2	3	<--	Brown	Brown / Yellow	4 (T-) & 5 (T+)
Transmit Data	3	2	<--	Violet	Orange/ Violet	2 (R-) & 3 (R+)
Request to Send	7	4	<--	N/C	N/C
Signal Ground	5	7	<--	Black	Black	9 (GND)

Note: Driving the RS-422 inputs on the Palisade single ended, i.e. using the Green and Gray connections,
does not work on all serial ports, and is deprecated. Use of the Palisade NTP host adapter is recommended.

Pinouts for the Palisade NTP host adapter (Trimble PN 37070) DB-25 M connector are as follows:
 
 

DB-25M	Conductor	Palisade	Description
1	Red	1	Power
7	Black	9	Ground
9	Black/White	12	PPS -
10	Green	8	Transmit Port A (T-)
11	Brown	4	Transmit Port B (T-)
12	Gray	7	Receive Port A (R+)
13	Orange	3	Receive Port B (R+)
21	Orange/White	11	PPS +
22	Blue	10	Transmit Port A (T+)
23	Yellow	5	Transmit Port B (T+)
24	White	6	Receive Port A (R-)
25	Violet	2	Receive Port B (R-)

The Palisade's secondary port, Port B, provides a TSIP (Trimble Standard Interface Protocol), control and command interface for diagnostics, configuration, and monitoring.
Port B and the PPS output are not currently used by the Palisade NTP reference clock driver.
 

O/S Serial Port Configuration

The user is expected to provide a symbolic link to an available serial port device.  This is typically performed by a command such as:

ln -s /dev/ttyS0 /dev/palisade0

Time Transfer and Polling

The driver requests an event time stamp at the end of each polling interval, by pulsing the RTS (request to send) line on the serial port. The Palisade receiver responds with a time stamped event packet.

Time stamps are reported by the Palisade with respect to UTC time.

Data Format

Palisade port A can output two synchronous time packets. The NTP driver can use either packet for synchronization. Packets are formatted as follows:
 

Packet 8F-AD (Primary NTP Packet)
 

Byte	Item	Type	Meaning
0	Sub-Packet ID	BYTE	Subcode 0xAD
1 - 2	Event Count	INTEGER	External event count recorded (0 = PPS)
3 - 10	Fractional Second	DOUBLE	Time elapsed in current second
11	Hour	BYTE	Hour
12	Minute	BYTE	Minute
13	Second	BYTE	Second (0 - 59; 60 = leap)
14	Day	BYTE	Date (1 - 31)
15	Month	BYTE	Month (1 - 12)
15 - 17	Year	INTEGER	Year (4 digit)
18	Receiver Status	BYTE	Tracking Status
19	UTC Flags	BYTE	Leap Second Flags
20	Reserved	BYTE	Contains 0xFF
21	Reserved	BYTE	Contains 0xFF

 

Leap Second Flag Definition:
Bit 0:  (1) UTC Time is available
Bits 1 - 3: Undefined
Bit 4:  (1) Leap Scheduled: Leap second pending asserted by GPS control segment.
Bit 5:  (1) Leap Pending: set 24 hours before, until beginning of leap second.
Bit 6:  (1) GPS Leap Warning: 6 hours before until 6 hours after leap event
Bit 7: (1) Leap In Progress. Only set during the leap second.
 

Tracking Status Flag Definitions:
 

0	Receiver is Navigating
1	1 Sat. Timing Mode
2	Approximate Time (20 - 50 ms)
3	Startup
4	Startup (N/A)
5	Dilution of Position too High (only applies during survey)
6	1 Sat. Timing Mode: SV is not usable
7	No Satellites Usable
8	Only 1 Satellite Usable
9	Only 2 Satellite Usable
10	Only 3 Satellites Usable
11	Invalid Solution (Serious Error Cond.)
12	Differential Corrections (N/A)
13	Overdetermined Fixes

 

Packet 8F-0B (Comprehensive Timing Packet)
 

Byte	Item	Type	Meaning
0	Sub-Packet ID	BYTE	Subcode 0x0B
1 - 2	Event Count	INTEGER	External event count recorded (0 = PPS)
3 - 10	UTC / GPS TOW	DOUBLE	UTC / GPS time of week (seconds)
11	Date	BYTE	Day of Month
12	Month	BYTE	Month of Event
13 - 14	Year	INT	Year of event
15	Receiver Mode	BYTE	Receiver operating dimensions:  0: Horizontal (2D)  1: Full Position (3D)  2: Single Satellite (0D)  3: Automatic (2D / 3D)  4: DGPS reference  5: Clock hold (2D)  6: Over determined Clock
15 - 17	UTC Offset	INTEGER	UTC Offset value (seconds)
18 - 25	Oscillator Bias	DOUBLE	Oscillator BIAS (meters)
26 - 33	Oscillator Drift Rate	DOUBLE	Oscillator Drift (meters / second)
34 - 37	Bias Uncertainty	SINGLE	Oscillator bias uncertainty (meters)
38 - 41	Drift Uncertainty	SINGLE	Oscillator bias rate uncertainty (m / sec)
42 - 49	Latitude	DOUBLE	Latitude in radians
50 - 57	Longitude	DOUBLE	Longitude in radians
58 - 65	Altitude	DOUBLE	Altitude above mean sea level, in meters
66 - 73	Satellite ID	BYTE	SV Id No. of tracked satellites

Configuration

peer terrapin.csc.ncsu.edu # internet server

# Drift file for expedient re-synchronization after downtime or reboot.
driftfile /etc/ntp.drift
#------------------------------------------------------------------------------

A typical ntp.conf configuration file for this driver and a Palisade without event polling:

#------------------------------------------------------------------------------
# The Primary reference
server 127.127.29.0 # Trimble Palisade GPS (Stratum 1).

# Set packet delay
fudge 127.127.29.0 time1 0.020

# and set flag2 to turn off event polling.
fudge 127.127.29.0 flag2 1

# Drift file for expedient re-synchronization after downtime or reboot.
driftfile /etc/ntp.drift
#------------------------------------------------------------------------------

Logging

Nov 14 16:16:21 terrapin ntpd[1127]: Palisade #0: message

Debugging

1. Place the Palisade GPS receiver outdoors; with clear view of the sky.
2. Allow the receiver 5 minutes to acquire satellite lock and position.
3. Verify presence of timing packets by observing the 1 Hz (PPS) led on the NTP interface. It should flash once per second.
4. Connect Palisade port A to the NTP host.
5. Configure NTP and the serial I/O port on the host system.
6. Initially use fudge flag2 in ntp.conf, to disable event polling (see configuration).
7. Run NTP in debug mode (-d -d), to observe Palisade_receive events.
8. The driver reports the tracking status of the receiver. A minumum of 4 sats. are required for self-survey to complete.
9. Remove fudge flag2 and restart ntpd in debug mode to observe event polling receive events.

 #DEFINEs

Fudge Factors

time1 time

Specifies the time offset calibration factor, in seconds and fraction, with default 0.0.

 time2 time

Not currently used by this driver.

stratum number

Specifies the driver stratum, in decimal from 0 to 15, with default 0.

refid string

Specifies the driver reference identifier, GPS.

flag1 0 | 1

Not currently used by this driver.

flag2 0 | 1

When set to 1, driver does not use hardware event polling. Instead, the synchronous packets output at the start of each second by the Palisade receiver are used. If the ioctl() call triggering the event capture fails, the driver falls back to this mode automatically.

flag3 0 | 1

Not currently used by this driver.

 flag4 0 | 1

Not currently used by this driver.

Additional Information

(last updated May 13, 1999)