The DM24 outputs diagnostic information in a status stream. This is a special GCF stream whose name ends in 00.
Status streams can take two different forms, depending on the current transmission mode:
In FILING mode, a short heartbeat message summarizing the current status is transmitted regularly at a configurable interval of between 10 seconds and a few minutes. The heartbeat message lets clients know that the digitizer is still operational, even though it is not sending data. For example, if you connect a PC running Scream! to an autonomous station over a dial-up link, Scream! can automatically download recorded data: this is made possible by the heartbeat message, which tells Scream! that the data exists.
In all other modes, status messages are output continuously, in GCF blocks. When each block is full, it is transmitted from the DATA OUT port with the rest of the data.
These are output at regular intervals, and always have the same format. Older digitizers may not include all the lines described here.
64MB Flash File buffer : 65,520 Blocks Written 65,520 Unread 16 Free
Latest data [392] PLPGG SBHYX2 2006 1 18 14:55:57
Oldest data [400] PLPGG SBHYN4 2005 11 30 06:47:38
# 22 2006 1 18 14:48:36 No File Last Event
2006 1 18 14:56:15 1 MicroSeconds Fast Freq error 0 e-9 Auto 3D [-4]
PLPGG SBHY00 CMG-3T
Boot Log : 143 Power cycles 294 Watchdog resets
Last boot 2006 1 12 16:18:57 2006 1 17 17:15:14
2006 1 18 14:56:15 External supply : 13.0V Temperature 24.68'C
2006 1 18 14:56:15 Mass positions -486 -300 -424
The first three lines describe the internal Flash memory. First, the overall usage is described:
64MB Flash File buffer : 65,520 Blocks Written 65,520 Unread 16 Free
Here, a 64 Mb Flash memory store contains 65,520 data blocks, of which none have already been downloaded. This leaves 16 blocks of free space, since each block is exactly 1Kb long, and (65,520 + 16) × 1 Kb = 65,536 Kb = 64 Mb.
Latest data [392] PLPGG SBHYX2 2006 1 18 14:55:57
Oldest data [400] PLPGG SBHYN4 2005 11 30 06:47:38
These two lines show the date and time of the oldest and newest data in the buffer, together with the System ID (PLPGG) and the Stream IDs (SBHYX2 and SBHYN4) of the corresponding data stream.
# 15 Filed @ 64,167 PLPGG SBHYZG 2006 1 5 10:31:30 Last Event
This line gives the date and time of the last trigger, together with its System ID and Stream ID as above. Also given is the event sequence number (15, here) as used by the EVENTSLIST command, and the position in the buffer where data from the event begins.
If a trigger has occurred, but no data was output (e.g. because the digitizer was in DIRECT transmission mode), the digitizer will report
# 22 2006 1 18 14:48:36 No File Last Event
The next line describes the current status of the GPS system. When the digitizer is first powered up, the message will be something like
2005 8 10 12:35:00 GPS control OFF Auto 3-D [-5 Not sync'd]
The message GPS control OFF denotes that the clock is not yet being controlled by the GPS. Owing to noise purposely injected into the GPS timing stream, as well as issues of signal travel time, the GPS time cannot be directly used to synchronize the clock. Instead, the digitizer maintains a rolling average of time measurements, and uses this to apply corrections to the clock so that it remains accurate over a long period.
The Auto 3-D message denotes that the signal is strong enough to obtain a full 3-dimensional GPS fix. If the signal is weak, or there are too few satellites visible to the receiver, you may see Auto 2-D here. If the signal is too weak to obtain a fix, No FIX will be displayed.
After a short time, the message will change to
2005 8 10 12:36:00 GPS Control settling Auto 3-D [-5 Not sync'd]
Eventually, the GPS control system will be able to synchronize the internal clock, and the message will change to
2005 8 10 12:38:01 GPS Control settling Auto 3-D [-4]
2005 8 10 12:41:01 326 MicroSeconds Slow Freq error -7 e-9 Auto 3-D [-4]
The system is now reporting the current offset of the internal clock from GPS time (whether slow or fast), and the current frequency error. It will now continuously adjust the internal clock for as long as the GPS is powered up.
If you have chosen to save energy by enabling GPS power cycling, the DM24 will switch off the GPS once a satisfactory fix is obtained, and begin free-running on the internal clock. Whilst this is happening, the line will report
2005 8 10 17:06:27 GPS switched Off
PLPGG SBHY00 CMG-3T
Boot Log : 143 Power cycles 294 Watchdog resets
Last boot 2006 1 12 16:18:57 2006 1 17 17:15:14
These three lines repeat information from the last re-boot:
in the first, the System ID, the Stream ID of the status stream, and the current Sensor Type;
in the second, the number of times the digitizer has been power cycled, and the number of times it has been reset without power cycling (e.g. by a re-boot after reconfiguring the module: a “soft” reset); and
in the thrid, the date and time of the last power cycle and of the last soft reset.
2006 1 18 14:56:15 External supply : 13.0V Temperature 24.68'C
The next line displays the current state of the DM24's power supply, and its internal temperature.
2006 1 18 14:56:15 Mass positions -486 -300 -424
The final line provides the instantaneous mass positions reported by the sensor at the time given.
In continuous mode, each status block contains a number of single-line messages:
2006 1 18 14:38:00 o/s= 90 drift= 0 pwm= 8187 Auto 3D
2006 1 18 14:39:00 o/s= 90 drift= 0 pwm= 8187 Auto 3D
2006 1 18 14:40:00 o/s= 90 drift= 0 pwm= 8187 Auto 3D
2006 1 18 14:41:00 o/s= 90 drift= 0 pwm= 8187 Auto 3D
2006 1 18 14:42:00 o/s= 90 drift= 0 pwm= 8187 Auto 3D
2006 1 18 14:43:00 o/s= 78 drift= -12 pwm= 8188 Auto 2D
2006 1 18 14:44:00 o/s= 89 drift= 11 pwm= 8188 Auto 3D
2006 1 18 14:45:00 o/s= 94 drift= 5 pwm= 8188 Auto 3D
2006 1 18 14:45:00 External supply : 13.0V Temperature 24.62'C
2006 1 18 14:46:00 o/s= 148 drift= 54 pwm= 8188 Auto 3D
2006 1 18 14:47:00 o/s= 174 drift= 26 pwm= 8188 Auto 3D
2006 1 18 14:48:00 o/s= 211 drift= 37 pwm= 8188 Auto 3D
2006 1 18 14:48:36 SOFTWARE Trigger : Trigger# 22
2006 1 18 14:49:00 o/s= 263 drift= 52 pwm= 8187 Auto 3D
2006 1 18 14:49:10 End of Trigger
The messages appear in the order they are generated by the different software modules inside the digitizer.
The status of the attached GPS receiver is reported every minute:
2006 1 18 14:47:00 o/s= 174 drift= 26 pwm= 8188 Auto 3-D
In this line:
o/s gives the current offset of the internal clock from GPS time, in arbitrary internal units;
drift is the difference between the current o/s and the last, which gives an indication of the level of drift;
pwm, or Pulse Width Modulation, is the feedback control parameter;
Auto 3-D denotes that enough GPS satellites are currently visible to obtain a full 3D fix. If, instead, No Fix is displayed, the GPS received has not (yet) been able to obtain a satisfactory fix. If Missing PPS is displayed in this field, the digitizer has received fewer than 60 pulses on the 1pps (pulse per second) line in the last minute. You will see at least one Missing PPS message in the first minute of operation.
Every 20 minutes, at 10, 30 and 50 minutes past the hour, the GPS synchronization status is displayed. This line has the same format as the GPS line in the heartbeat message, e.g.
2005 8 10 12:41:01 326 MicroSeconds Slow Freq error -7 e-9 Auto 3-D [-4]
Finally, every hour, the DM24 displays general timing and position information, including details of the visibility of GPS satellites:
2005 6 8 11:00:00 GPS Date/Time 08/06/05 11:00:00
2005 6 8 11:00:00 Auto 3-D SV#'s 4 7 13 20 23 24 25 ( 7 )
2005 6 8 11:00:00 Lat 51'21.6591N Long 001'09.8218W
SV# stands, officially, for Space Vehicle number. Each GPS satellite has it's own unique identification number, or SV#, and the list shows which are currently usable (satellite numbers 4, 7, 13, 20, 23, 24 and 25 in this example). A minimum of four is required to obtain a full 3-dimensional GPS fix.
When a trigger occurs, a message is immediately saved to the current status block. You may not see this message straight away, however, since the status block must be full before the digitizer will send it.
2006 1 18 14:48:36 SOFTWARE Trigger : Trigger# 22
The trigger type is mentioned, as well as the sequence number (for later retrieval, if necessary, using the EVENTSLIST command). When the trigger condition ends, the system reports
2006 1 18 14:49:10 End of Trigger
These are measured every 10 minutes (at 5, 15, 25, 35, 45 and 55 minutes past the hour), and are given in the same form as for heartbeat messages:
2006 1 18 14:45:00 External supply : 13.0V Temperature 24.62'C
You can update the digitizer firmware using any terminal program which supports the Xmodem protocol, such as minicom, hypertrm or newer versions of Scream!. If you are using Scream!, right-click on the digitizer’s icon in the main window and select Terminal from the pop-up menu:
Scream-terminal-window
Check that there is two-way communication with the digitizer by pressing Enter. The digitizer should reply with ok on a new line.
Type re-boot to reinitialize the digitizer, and confirm with y. As it is restarting, the digitizer will report its status over the terminal connection, followed by a maintenance menu:
MPE ARM ANS ROM PowerForth v6.20
ARM Serial BootStrap v1.100, 11 August 2003
Copyright (c) 2002-3 GSL, EDSL & MicroProcessor Engineering Ltd.
Port 0 38400 baud
Port 1 38400 baud
Port 2 38400 baud
Guralp Systems Ltd - ARM-BOOT v01.0 mgs 29/07/04 [b 015]
System Code versions loaded :-
0103:0000 Guralp Systems Ltd DMARM v01.0 mgs 09/07/04 [Build 017]
0107:0000 Guralp Systems Ltd - DM+FW v01.1 mgs 11/08/04 [Build 007] Default
010B:0000 Blank
DSP Code :
0101:0000 ARMT16D16-050304.BIN
0102:0000 dsprot037.bin 04/08/04 Default
Command keys:
C - set real time Clock (2004 8 13 09:29:48 )
I - view/upload InfoBlock
F - run the Forth monitor
R - Run an application
E - Erase an application
S - update System program
B - update Boot program
D - update DSP code
N - set the default application Number (3)
Q - Quit maintenance system
3 seconds to auto-start
Enter command:
If you do not press a key in the next three seconds, the DM24 will start up normally.
The DM24 has three firmware components, which can be updated separately: the system program, the DSP code and the boot loader. Firmware releases are available on the Güralp Systems website. If a release updates more than one component, you should be sure to update the boot loader first, then the system program and DSP code.
To update the system firmware, press S at the maintenance menu. The digitizer will display
Update System program
There are three slots available for system application code. The digitizer will use the slot following the one currently set as Default. You should note which slot is currently in use, so that you can revert to the old firmware in case of a problem.
The digitizer will then request a transfer using the Xmodem protocol. If you are using Scream!, a file browser window will appear automatically.
Navigate through the directories on your computer and select the file to be uploaded, or type in its full path and file name. Click Open.
DM24-select-file-to-transmit
Whilst the file is loading, a progress window will be displayed. Depending on the speed of the link, it may take up to 20 minutes to transfer the firmware.
Once the file is fully transferred, the DM24 will return to the maintenance menu. Press ENTER, and wait whilst the system boots.
You can run system code other than the default by pressing R at the maintenance menu, followed by the slot number of the new code. This will run the DM24 with the new firmware for one session only. When it is rebooted, the DM24 will revert to the Default application.
Press D at the maintenance menu. The digitizer will reply with
Enter 0/1 to select DSP code to update
Select which of the two DSP code slots you want to overwrite, and press ENTER. The default is always 0.
Enter Filename/date – upto 31 characters
You can enter a descriptive string for the DSP code here. The DM24 will print this string at every boot-up, to remind you which version of the DSP code you are using.
When you press ENTER, the digitizer will then request a transfer using the Xmodem protocol, as described above.
There is only one slot available for the boot loader. Press B at the maintenance menu to update it.
The digitizer will then request a transfer using the Xmodem protocol, as described above. Be sure to check beforehand that the file is a valid DM24 boot loader! Replacing the boot loader with invalid code will make it impossible to boot up the digitizer. If in any doubt, please contact Güralp Systems technical support for advice before proceeding.
When you are returned to the maintenance menu, press Q or wait 30 seconds for the system to restart.
Güralp digitizers and digital instruments can be supplied with external triggering capabilities installed. The external trigger system is designed for maximum flexibility: you can trigger other digitizers or your own equipment using built-in relays, or any equipment may be used as a trigger source. In addition, a trigger circuit can link together any number of digitizers so that they trigger simultaneously when they receive a signal.
The digitizer or digital instrument has two internal components related to triggering.
The trigger generator runs the triggering algorithm and determines whether a trigger has occurred. If external trigger output has been enabled, the trigger generator also operates a relay which connects the two Trigger Out pins of the DATA OUT port. These are normally pins E and F.
The Trigger Out pins are only connected whilst the generator is active. This does not include any pre-trigger or post-trigger period, which is dealt with by the trigger receiver. A trigger signal may be as short as one second.
The trigger receiver acts upon trigger signals: normally, by recording additional data streams. The receiver will always start recording if the trigger generator produces a signal. If external trigger input has been enabled, the receiver will also act on a logic signal received on the Trigger In pin of the DATA OUT port.
Any signal between +3 and +30 V referenced to power ground (pin A) can be used. The instrument's own power supply (pin B) could be connected via a relay to supply this signal, for example.
The Trigger Out pins are not connected if you provide a Trigger In voltage. The instrument must trigger itself for the relay to switch. This arrangement prevents any trigger loops from occurring.
The diagrams on this page show the additional connections you will need to make. Pins A and B, and the data pins, should be connected to your power and data systems as normal.
If your equipment can trigger from 24 V DC, the simplest arrangement is to use the voltage across the sensor's power supply as a trigger.
Connect the ground pin A to your equipment's trigger return line. If your equipment does not have a separate trigger return line, consult its documentation for how to apply trigger voltages. Güralp digitizers use the power ground line as a trigger return. (The diagram above does not show the power supply to either the sensor or the triggered equipment: only the triggering system is shown).
Because a trigger signal may last for only a short time, inserting pins E and F directly into your equipment's power circuit is not normally advisable. Ideally, the equipment should be continuously powered and listening on dedicated trigger input lines. If this is not possible, it may be enough to build a control circuit with a time-out period, which supplies your equipment with power for a suitable minimum length of time whenever pins E and F are connected.
The digitizer cannot anticipate a trigger. Pre-trigger recording is achieved using a continuously-updated buffer of the most recent data. Any external equipment must have its own buffering capabilities if you need pre-trigger data.
Connect pin B to pin E, and pin F to your equipment's trigger signal input.
Connect the remaining pins as normal.
If your equipment needs a different voltage, you will need to provide a separate voltage source for the triggering system. Be careful not to connect two power supplies together. The instrument's power supply can be protected by inserting a diode from pin B to pin E (see below).
To trigger an instrument from an external source through a relay:
Connect a the normally-open switch contacts of a suitable relay between pins B and H, with the coil connected to your generator so that pins B and H are connected when a trigger occurs.
The relay allows you to power the external generator from any source. This includes the instrument's own power supply at pins A and B, if it is suitable.
Connect the other pins as normal.
If you prefer, you can use a separate power source for your trigger generator. However, because pin H is referenced to power ground, the external power supply must share a common ground with that of the digitizer, so you should connect the power supply ground to pin A.
A common use of the external triggering feature is to ensure that all instruments in an array trigger at the same time. This can be achieved with the wiring layout below. With this arrangement, any instrument can generate a trigger, which will be passed on to all the instruments in the array.
For each instrument:
pin A is connected to a common ground;
pin B is connected to the instrument's power supply as normal and also to pin E through a diode (an IN4001 is suitable);
pins F and H are connected to each other and to a common trigger line; and
the remaining data pins are connected to your recording equipment as normal.
The diode at pin E is important, because if two instruments generate a trigger simultaneously, their power supplies will both be connected via the internal relay contacts to the common trigger line on pins H, and hence connected together. This can cause considerable current flow with consequent risk of fire, as well as severe damage to equipment and cables.
In the case where a single power supply is used to power all of the equipment, this is not an issue and pin E should be connected directly to pin B on all units. Pin B should then also be connected to the power supply's positive terminal.
The more common case, where each unit has it's own power supply, is shown below. Power supply wiring is omitted for the sake of clarity but note that all the power supply's ground terminals will be connected together via the links between pin A on each unit. The power supplies must, therefore, have floating outputs or grounded negative terminals.
Internally, DM24 digitizers are structured as shown in the following diagram, where each box represents a separate internal subsystem.
DM24mk3-block-diagram
The system is designed around a low power, high performance ARM microprocessor. This is a 32-bit processor with a large address space for data storage and manipulation. It also includes many integrated functions such as multiple timers and serial I/O ports. In addition, the system contains a Cirrus Logic CS5376 digital filtering chipset and TMS320VC33 digital signal processor (DSP). The CS5376 provides data to the DSP at 2,000 samples per second, triggered by timing signals from the ARM processor. The DSP can control all 5 ADCs and process the data in real time.
An important feature of the system design is its ability to synchronise the sampling of the analogue to digital converter to an external time reference. This way, data samples are accurately time stamped at source. To keep sampling accurately in step with UTC, the microprocessor's time-base is synchronized to an external reference, derived from GPS or, in larger arrays, to a centrally-transmitted time reference. Sharing a time reference avoids the cost and power consumption of multiple GPS receivers and, since it only involves sending 2 characters per second, it can utilise a low bandwidth link.
To achieve the high degree of timing precision required for a 24-bit digitizer system, the microprocessor time-base is run from a precision voltage controlled oscillator. On-board software keeps this oscillator tuned to the external reference so that its frequency is accurately set and maintained through changes in temperature or ageing. Once the system has stabilised, the control is sufficiently accurate to maintain precision sampling for several days without an external reference. The system also automatically compensates for the pure time delay introduced by the digital filtering/decimation processes in the DSP.
The DSP software consists of 6 cascaded programmable filter/decimation stages, which allow you to select multiple data output rates simultaneously. Each stage can be set individually for decimation factors of 2, 4, or 5. Data can be output at any or all of these rates. For example, a system can be configured to provide data at 200, 50, and 10 samples/sec, covering the whole of the seismological broad band range. The configuration of the DSP is programmable in the field via the host ARM microprocessor.
The primary digital interface is the multiple serial port card, which allows the DM24 to support up to 8 serial ports using the ARM's on-board UARTs (Universal Asynchronous Receiver/Transmitters). On a DM24 with analogue inputs, one serial port is usually configured to send the data packets to a local SAM or DCM unit for storage or, via a modem or radio link, to a central recording station. A second serial port is often used with a local GPS receiver for time synchronization, or, alternatively, the first (data) port can be used for time synchronization from a central station.
The UARTs and serial port module are optically isolated to avoid any ground loops that could degrade the performance of the ADC’s. The serial port module also includes 32k of RAM for data buffering and formatting by the transmission/reception process.