                                  

                     Help File for the GpsNav Application
                     ====================================

 0. Contents:
 ============

   1. About GpsNav
   2. About this Help File
   3. About the Rockwell Microtracker(TM) LP GPS Receiver Module
   4. GpsNav's Main window
   5. The Button bar and associated windows/alarms
   6. Bugs/oddities 
   7. Version history
   8. Legal/Copyright
   9. Acknowledgements
   10. Contact information
   

 1. About GpsNav
 ===============

   GpsNav is a limited Interface application for the Rockwell
 Microtracker(TM) LP GPS Receiver module. This module is supplied in an
 evaluation package for OEM's or experimenters, together with accessories
 (power supply, batteries, cables etc), a comprehensive manual and DOS
 interfacing software.
   
   GpsNav was written as a limited ("lite") application  to cater for the
 more useful functions provided by the Microtracker(TM) GPS Receiver. Even
 so a lot of varied data is read from the Receiver, requiring a large
 Main window with over 160 icons to display them, while another transient
 window with nearly 90 icons displays the Built In Test (self-test) results
 on demand. Initialization and control data are entered in smaller windows.

   The Microtracker(TM) LP GPS Receiver can operate in two general modes,
 Binary and NMEA (National Marine Electronics Association) modes. The latter
 is a standard used mainly in the USA, while the Binary mode is general-
 purpose and it is for this that GpsNav has been written. 

   The various data transmitted or received by the GPS Receiver, via its 
 Serial port, are  grouped in "Messages" of different size. GpsNav can 
 receive and display  three of the output Messages, Message 101 
 (Built-In-Test Results), Message 102 (Visible Satellite Information) and
 Message 103 (Receiver Position, Velocity, Time and Status Information). Of
 these, Message 101 is  sent by the Receiver only on request, triggered by
 clicking on a button in the Main window. Message 102 is sent every two
 minutes or after a BIT (Built-In-Test) is requested. Message 103 is sent
 every one second by default, unless specified otherwise by the Power
 Management Message (described in Section 5).

   GpsNav can also send a number of initialization and control Messages to
 the GPS Receiver: Message 201 (Initialization Command), Message 202 
 (Built-In-Test Command) and Message 211 (Power Management Control). These
 are initiated from the Button bar and details are given in Section 5. 

   Among data provided by the GPS Receiver is the current UTC Time and Date.
 GpsNav can enter this information into the Computer's clock, provided the 
 Receiver is in Navigation mode and the UTC Validity Flag is raised. More
 details on this function are provided in the description of the Button bar.

   GpsNav is a Desktop multitasking application. It has been tested with a
 few other applications and no problems have been encountered. However,
 GpsNav uses the Serial port to communicate with the GPS Receiver, so it
 cannot be  used by other applications. Also, GpsNav multitasks by using
 the Null event to monitor the Serial port for data, so each time the
 Receiver sends a  Message (normally once a second for Message 103), GpsNav
 holds up the processor for the duration of the transmission. This is about
 150 msec per second, unless Message 103 is configured to transmit at wider
 intervals (maximum  of once every 5 sec).

   GpsNav is written in WimpBASIC, Clares' new programming language. It needs
 WBModules, WimpBASIC's run-time module, in order to run. This is available 
 WimpBASIC' dedicated website (http://www.treknet.is/wb/) and is also
 supplied with this application.

 
 2. About this Help file
 =======================
 
   The Rockwell Microtracker(TM) LP GPS Receiver module, although easy to
 use, has a wealth of features and can provide or accept a wide range of data.
 The Development package is provided with a very detailed and comprehensive
 instruction manual that describes all aspects of the Receiver and the GPS
 (Global Positioning System) satellite navigation system. It would be out of 
 place and far too extensive to duplicate all this information in this help
 file, so this is limited to describing the GpsNav application and its use.  
 Anyone wishing to experiment with the Microtracker(TM) LP will need to have
 a good look at Rockwell's manual to learn about the GPS System and the 
 Receiver, and to understand the functions provided by GpsNav and the 
 terminology used in this Help file. 


 3. About the Rockwell Microtracker(TM) LP GPS Receiver module
 =============================================================

   This Rockwell GPS Receiver module is very small (51 x 71 x 9 mm) and has a
 low power consumption. With a supply of 5v, average power consumption is
 about 850 mW. This can be reduced to about 425 mW when in Power Management
 mode (Navigation Update rate 5 sec). The Receiver has 5 parallel channels
 so it can track up to 5 Navstar satellites simultaneously. However, one
 channel is used to search and track up to 5 more satellites so at any time
 a maximum of 9 visible satellites can be monitored by the Receiver.

   To provide position and velocity data, the Receiver needs to track 3
 visible satellites but can only operate in one of its 2-dimensional
 navigation solution modes. With 4 satellites tracked, a normal 3-dimensional
 solution can be achieved automatically. Details of these function are
 provided in the instruction manual.

   The Microtracker(TM) LP uses Rockwell's CityTracker(TM) software which 
 improves tracking in urban or forested areas or under conditions of vibration
 and shock. Vehicle dynamics up to 950 m/s and 4g are supported.

   For maximum battery life in portable equipment, Power Management and "Keep
 Alive" modes are available to reduce power consumption. The receiver can be
 used with an active or passive antenna for design flexibility. Direct
 differential RTCM SC-104 protocols are supported which reduce the maximum
 position error from 100 m to 5 m. Both Binary and NMEA-0183 protocols are 
 supported.

   For more details please refer to the instruction manual.


 4. GpsNav's Main window
 ==================

   GpsNav's Main window displays data from all three Messages catered for by
 this application, although from Message 101 (BIT) only the Receiver Health
 Summary results are shown. A complete and detailed display of the Built-In-
 Test results are shown in a separate pop-up window that appears when a BIT is 
 requested. When GpsNav is started by clicking on the Iconbar icon, the Main
 window opens and the various icons display the format and range
 (maximum value) of each data item. 

   As far as possible, data from the Receiver is displayed in icons grouped
 according to function, in walled borders. Each group has a descriptive title
 bar with a blue background. Each data icon has its own descriptive title (to
 its left) in a grey background. Data icons mostly have changing background
 and foreground colours, depending on the Receiver's status and the validity
 of the displayed data. Some icons display various status flags and may show
 a white "tick" in green background for a valid or positive condition, a
 question mark in an orange background for an undefined or pending condition
 or an "X" in a red background for an invalid or negative condition.

   The main Navigation (Receiver Position) data are displayed in a group of 
 icons in the top three rows of the Main window. These are Latitude North,
 Longitude East and Altitude, the well-known position co-ordinates as used
 in Marine, Land and Aerial navigation. Latitude and Longitude are given in
 degrees, minutes and seconds to three decimal points (ddd:mm:ss.xxx). 
 Altitude is given in meters, to three decimal places. Position data are also
 given in Cartesian (X Y Z) co-ordinates, a system not commonly used, also 
 in meters to three decimal points.
 
   Velocity data is given in meters/sec to three decimal points, for
 Horizontal Velocity North and East and Vertical Velocity Up. All these are
 given according to the WGS84  Earth-Centered Earth-Fixed (ECEF) co-ordinate
 system, adopted by the USA's military and used by the GPS system, while the
 North, East and Up directions are given as positive values.
   
   Various errors are involved in the measurement of Position data and the
 GPS Receiver provides some estimates for these. The cause for these errors
 is explained in the GPS Receiver's instruction manual and is not duplicated
 here.  The various error estimates are displayed in icons grouped in the
 left side of the Main window and under the Position data group. 

   Information on visible GPS Navstar satellites is provided by the Receiver
 in Message 102 and is displayed in a group in the centre of the Main window
 under the Position data group. Up to nine satellites can be tracked by the 
 Receiver and the information provided for each is the PRN, and Elevation
 and Azimuth in degrees. The number of visible satellites is indicated in
 the blue title bar and if there are less than nine visible, data in the
 icons is replaced by "x"'s.

    The background and foreground colours of the above groups of data icons
 change according to the Receiver's status. While this is in the Cold Start
 or Acquisition mode, the values in the various data icons are fetched from 
 the Receiver's EEPROMS, which hold the last valid measurements. Until the 
 Receiver tracks enough Navstar satellites to go into Navigation mode, the
 background colour will be red and the foreground colour white. Once
 Navigation  mode is achieved, background becomes green and foreground black.

   To the right of the Message 102 group, the activity of the five channels
 of the GPS Receiver is indicated in a group of icons that indicate, for each
 channel: Satellite PRN, activity (Idle, Search, Track

   The GPS Receiver provides UTC Date and Time data as well as other time 
 measurements relating to the GPS system. This information is displayed in
 icons grouped in the right side of the main window, under the Position data
 group. While the Receiver is not tracking any Navstar satellite, as in the
 Cold Start or Acquisition mode, time and date icons will have a red
 background and white foreground, and the displayed data will be incorrect.

   As soon as any satellite is acquired and tracked, time and date data become
 available and are displayed, however the UTC Validity flag is not yet raised
 by the Receiver. Under these conditions, the time and date icons will have
 an orange background and black foreground. When enough satellites are
 acquired and tracked, the Receiver goes into Navigation mode and raises the
 UTC Validity flag. Icon background then becomes green and foreground black.

   In the bottom left of the Main window, a group of "flag" icons indicate
 the results summary of the Built-In-Test (self test) of the Receiver. This
 is carried out on demand only and is initiated by the "scope" BIT Request
 button in the Button bar. The "pass" condition is indicated by the "tick"
 flag and fail by the "X" flag. During the execution of the BIT, which takes
 about 10 sec, these icons carry the "questionmark" flag. A count of Serial
 port transmission errors is also provided by the BIT results Message 101,
 displayed in the bottom right of the Main window.

   A group of "flag" icons in the bottom right of the Main window provide
 information on the status of the Receiver engine and its mode of operation.
 Details of these are explained in the instruction manual and are not 
 duplicated here.  The most useful are the  Mode icon (COLD, ACQ, NAV-2D
 or NAV-3D), the Figure of Merit of the Navigation solution, Number of
 satellites in the Navigation solution, the UTC Validity flag and the Power
 Management flag. 


 5. The Button bar and associated windows/alarms
 ===============================================

   GpsNav's Button bar is at the left vertical edge of the Main window and
 has the following indicators/buttons:
 
   a. The "Traffic Lights" Status indicator
   ========================================
   
   The top icon has the "Traffic-lights" status indicator. When GpsNav is 
 started by clicking on the Iconbar icon, the Main window opens with the 
 various icons displaying the format and maximum range of data values.
 However, at this stage GpsNav does not read or display any data from the 
 GPS Receiver and the status indicator shows the red light.

 To start GpsNav, the green "GO" button must be clicked but the state of
 the traffic lights will depend on the Receiver's mode. If this is in the
 Cold Start condition, e.g. searching for Navstar satellites with no
 initialization data supplied, the traffic lights will show the red light.
 If the receiver is in Acquisition mode, e.g. has valid initial position
 and time data supplied or has progressed from the Cold Start condition,
 the traffic lights will show the red and orange lights, e.g. an
 intermediate state.

   Finally, when the Receiver reaches the Navigation (2- or 3- dimensional)
 Mode, the traffic lights will switch to the green light and all the icons
 that display data from Message 103 (Position data) will turn to green
 background. Time and Date icons may remain in orange background, if the
 UTC Validity flag is not raised, as when the Receiver is put into the
 Power Management (low power) mode. Message 102 (Satellite Information)
 is sent every two minutes and it may take a short while for the icons
 in its group to change to green colour.

   Changes in the Traffic lights status indicator also trigger the system beep.
   

   b. The "GO" button
   ==================

   The green GO button below the traffic lights starts the operation of
 GpsNav. Data is read from the Serial port, processed and displayed in the
 appropriate icons. The state of the traffic lights will change as above.
 If there is no signal from the GPS Receiver (e.g. if it switched off or
 it is not connected to the Serial port) an alarm banner will show and
 the computer will beep.

   c. The "STOP" button
   ====================

   The red STOP button stops GpsNav and freezes the displayed information.
 It is mainly useful for taking readings from the Main window. When GpsNav
 is not running, the functions of all buttons except GO and Quit are 
 suspended.

   d. The "Scope" BIT request button
   =================================

   This button sends a BIT Request command to the GPS Receiver. A BIT
 Results pop-up window will also appear and GpsNav will stop running
 while the Built-In-Test is in progress. The red traffic light is shown
 and the computer beeps. If the Receiver does not acknowledge the BIT
 Request within 1 sec, an alarm banner will show together with the beep.
 If no BIT results, e.g. Message 101, are received within 12 sec, again
 there will be an alarm banner and a beep. 
   
   Initially, the BIT Results window will indicate the questionmark in
 the flag icons, while the icons, displaying data generated by the BIT,
 will have a red background. When Message 101 is received, the flag icons
 will indicate the pass/fail conditions, for the various receiver
 functions, with the "tick" or "X" flag. Icons displaying BIT data will
 turn to green background if the results are good. Any incorrect results
 will leave the  icons with a red background. If needed, the BIT can be
 repeated by clicking the Retry button in the BIT Results window.
 
   Detailed description of the BIT results is given in the Receiver's
 instruction manual and will not be duplicated here.

   e. The "sunny face" Warm Start button
   =====================================

   The "Warm Start" or Initialization button opens a window into which the
 Receiver's initial position and the current UTC time and date are entered.
 This information speeds up the acquisition and tracking of Navstar GPS 
 satellites, provided a current almanac of satellite orbital parameters
 is stored in the Receiver's EEPROM. An almanac remains valid for a few
 months and is renewed from data supplied by the satellites themselves.
 The initial position of the receiver is specified in degrees and minutes
 of Latitude North and Longitude East and can be within about 100 km of
 the  exact value. The altitude is specified in meters and can also have
 an  error of a few hundred meters. Time must be within about 5 min of
 UTC. Note that Year is entered with all 4 figures.

   When the GPS Receiver is switched off, it stores the last set of data
 in its EEPROM and when switched on, these are transmitted while satellite
 acquisition is in progress. If the Receiver has not been moved by more 
 than about 100 km while switched off, then the "Re-enter GPS Receiver's
 retained Position data" option can be selected and positional data will
 be entered from the Main window. And if the computer's time is in UTC,
 then this can be entered in the Warm Start window by selecting the
 "Enter UTC Time and Date from Computer's clock" option. 

 f. The "battery" Power Management button
 ========================================

 This button opens the Power Management parameters window. The first entry
 is the time interval in seconds between navigation solution updates. This
 parameter has a range of 1 to 5 sec maximum. A value of more than 1 will
 put the Receiver in the Power Management mode and the Power Management
 flag will be raised and indicated by the "tick" in the relevant Status
 icon. Normally in this mode, the UTC Validity flag is dropped and this
 is also indicated by the "X" in the UTC Validity icon.

   The second entry is the Acquisition Mode Time-out. A value of hex FFFF
 (-1) commands the Receiver to disable the time-out so that it remains in
 Acquisition mode until Navigation mode is achieved. Values of less than
 90 sec are interpreted as 90 sec, except for zero. A value of zero
 commands the Receiver to ignore this word and to continue using the
 previous time-out. Default is Time-out disabled (hex FFFF, e.g. -1).        

   The last entry is Low Power Operation Time-out. A value of hex FFFF
 (-1) commands the Receiver to remain in Low Power mode until switched
 off or reset. A value of zero commands the Receiver to ignore this word
 and continue using the previous time-out. The default value is 90 sec
 but in this application hex FFFF, e.g. -1 is set in the writable icon.

   If all this sounds confusing (and it is!), just leave the last two
 entries at default values.


 g. The "clock and calendar" Set Clock button
 ============================================

 As long as the UTC Validity flag is raised by the Receiver, clicking this 
 button will set the computer's clock to the GPS time and date (UTC). Note
 that if the Receiver is in Power Management mode, the UTC flag is dropped.

 h. The Quit button
 ==================

 The lowest button in the Button bar quits GpsNav, and can be used instead
 of the usual Quit entry of the Iconbar menu.

 
 6. Bugs/oddities
 ================

   A mysterious "Houdini" bug caused the original version of this application
 to simply disappear from the screen and the Iconbar after a few minutes
 of operation! It was never found but was flushed out by changing the design
 of GpsNav. See the version history for more details.

   On some occasions the system beep may sound twice in quick succession. This
 happens when the receiver occasionally toggles between different states but
 this does not effect the application's operation.

   When the GO button is clicked, GpsNav makes a claim for the Serial port by
 using the Wimp_SendMessage SWI and related protocols. However, results seem to
 be mixed so it is best not to run GpsNav with other tasks using the Serial
 Device, it will only work while it "owns" the Serial port anyhow.

 7. Version history
 ==================

 Version 1.00 
 ============
 
 This was the first functional version but was rather limited and it had a
 bug which caused the application to quit itself after about 15-30 minutes
 of running. The bug was never found so this version remained in the works.

 Version 1.01
 ============
 
 The bug above was killed by changing the design of GpsNav. In version 1.00,
 data transmitted by the GPS Receiver was converted to Acorn formats as it
 arrived and was stored in an array until the the data checksum was received.
 If this was valid, the data were then loaded into the Main window icons for
 display. In version 1.01, incoming data were stored in raw form in a block
 in memory until the checksum was verified, before converting and displaying.
 This flushed out the bug but it still remained a mystery!

   In this version, the design of the Main window was also changed to remove
 a number of redundant icons and to improving the grouping of like icons.
 This also reduced the size of the window and allowed the uncovering of the
 Iconbar. The Initialization Command (Message 201) was included in the
 supported functions together with the Power Management Command (Message 211).

 Version 1.02
 ============
 
 The style of the Main window was changed to improve its appearance and
 dynamic changing of icon background and foreground colour was introduced.
 This was done to make the assessment of the displayed information easier,
 since there is a large amount and variety of information in the Main 
 window. A pop-up window was also added to display the full details of the
 Built-In-Test when the BIT Request button is pressed.


 8. Legal/Copyright
 ==================

 a. Acknowledgement: Microtracker(TM) is a Rockwell Corporation Trademark.
 ===================

 b. GpsNav Application:
 ======================
 
   GpsNav is Freeware. It may copied and distributed free of charge only and
 Public Domain libraries may charge copy and distribution expenses. GpsNav
 must not be changed or partially copied without prior permission.

   GpsNav is provided as is. No guarantee can be made as to its suitability
 for any purpose or its functional integrity. No responsibility can be 
 assumed by the author for any damage or any loss incurred while using GpsNav
 for any purpose. 

   Because of its nature as an interface to particular hardware, GpsNav has
 only been tested extensively by the author and no independent assessment of
 its functions is available.

 9. Acknowledgements:
 ====================
 
   My thanks are due to David Jackson of Clares Micro Supplies for his help with
 WimpBASIC usage and advice on programming problems. Also to Gardar Gislason of
 WimpBASIC website for his help and the availability of example and
 application files on his website. 

 10. Contact details
 ==================

 Please send any comments and bug reports to:

 Neoklis Kyriazis
 Feakon 4
 Lemessos
 Cyprus 3117

 EMAIL: n.kyriazis@cytanet.com.cy 
 
  
 
 
 
 
 

   
   