You can also have an "outboard" (remote) compass rose display - here's how!

Please note:  This is not an official page of VE2EMM:  Please read the disclaimer below.

Replacement firmware is now available for the Compass Rose display for the Montreal Doppler III unit (even using Jacques' original firmware) that offers a number of enhanced features:
 

Using the compass rose with the Montreal Doppler II unit. Using the Alternate Firmware, this same software may be used with the older Montreal Doppler II unit to provide a compass-rose display.  This firmware adds the capability of a synchronous data stream to the Doppler II:  For more information on how it is connected, see the Doppler II modifications page.

• Three-color display:
• The current ("integrated" - but "un-averaged") bearing is shown in green while a bad bearing is shown in red and the averaged bearing is shown in yellow.

• Display of average direction:
• The "averaged" direction is displayed in yellow.  There are three modes of bearing averaging:
• A sliding average:  This consists of the 16 most recent "good" bearings.
  
• A running average: This consists of the average direction of all "good" bearings since the unit was powered up or since the average was reset.
• True average, as calculated by the main Doppler unit, the number of averages being adjustable via the main Doppler unit..  This feature is only available with Compass Rose firmware versions 2E and newer in conjunction with Doppler Firmware version 7A and newer.
  
• The use of an averaged bearing can help the user identify possible trends or "biases" in bearings on extremely weak or "multipathy" signals.  Additionally, the averaged bearing continues to be displayed even after the signal has disappeared.
• An average (in the first two mode) may be reset at any time.
• If desired, the "average" display may be turned off.
 
• "Bearing History" display:
• If desired, the past 15 "good" bearings may be displayed more dimly than the current bearing as to avoid confusion.  This allows the user to glance down at the display and note the "quality" of the recent bearings, to help identify trends, or, if the signal has since disappeared, to see the last several bearings.  This feature may be turned off at any time.

• Dim/Bright display selection:
• When using the suggested type of dual-color LEDs (see below) the display, when in "bright" mode, may be used in daylight.  While not bright enough to easily be seen if direct sunlight is flooding the display, it is very readable if placed out of direct sunlight.  If the user also turns off the "Bearing History" display, the LEDs are even brighter.
• At night, a bright display may be too bright:  The "Dim" setting makes the display more comfortable to look at in the dark.

• Display "flipping":
• The display may be "flipped" (as if in a mirror) so that east is on the left and the west is on the right.  Why do this?  This allows a reflection of the compass rose to be viewed with the bearings in their proper orientation.  An example of where this may come in handy is if the display is placed on the dashboard of the vehicle:  The result is a rudimentary "heads-up display" where the compass rose appears, floating, in the windshield.  While it is not recommended that a single person drives the vehicle and operates the DF unit, this facility allows the passenger/navigator to do his/her job while looking out the window (and maybe avoiding getting carsick...)

Front and back views of the (modified) compass rose display.
Click on either image for a larger version.

Required modifications:

Because of the expanded capabilities, there are a few simple modifications required to update a currently-operational display. Note that this software is not fully usable unless dual-color LEDs are installed -  but it can be used with single-color LEDs if appropriately configured - see below!

Replacing the LEDs:

All 36 of the compass-rose LEDs (LED1 - LED36) must be replaced with (or originally installed as) dual-color units.  The recommended LEDs are T1-3/4 sized and, if the LEDs originally suggested by Jacques (in his first version of the compass rose) had been used, this will require drilling larger holes in the front panel.

The LEDs recommended for the compass are DigiKey P/N: 160-1038-ND which is Liteon P/N: LTL-293SJW.

The Liteon LTL-293SJW is same type as originally recommended by Jacques for the center LED on the older versions of the compass rose.

The newer versions of the compass rose board (e.g. version 3.2) specify the use of a 3-lead dual-color LED - see below for more info.

Note that the center LED (LED37) need not be changed on the "pre-Version 3.2" boards.

Different two-color LEDs may also be used as long as they are of the two-lead variety where color (red/green) is determined by polarity of the applied voltage.  Note that the use of different LEDs may cause the "yellow" (a mixture of red and green) to be either too "greenish" or "red-ish" - depending on the relative brightness of the green/red emitters in the LED.  If this is the case, the color may be "tuned" slightly by the selection of an install option or, if that doesn't work, by the addition of resistors/diodes - contact me (at the email address below) for details.

• Note:  As originally designed, the dual-color LEDs, when used with this alternate firmware, were to be mounted backwards - that is, for LED1, the parts-placement drawing shows the the flat part of the case facing up - but this dual-color LED should be mounted such that the flat spot on LED1 is facing down.  In other words the green cathode is connected to the current limit resistors, R1-R6.
• Important note:  If you do install the 36 compass-rose LED as shown in the original diagram (that is, they are not backwards) don't worry:  Firmware versions 2E and later have a "polarity reversal" mode (see below) that can be used correct this.
• If you use dual-color LEDs other than the Liteon device specified, verify polarity (and test) before mounting all of them.  Please note that the firmware will default to a duty cycle that was intended to provide a yellow color for the specified LEDs.  If your "yellow" color is too "red" then you may need to adjust the color mix as mentioned below.

• The Center LED:  Remember that the center LED is mounted as shown in the parts-placement drawing, as this is the LED called out in the original parts list when using the original versions of the boards..

• The 3-lead LED CANNOT be used with this firmware!  Because the firmware relies on the ability to detect the three possible states of the mode switch (e.g. ground, V+, and floating) the LED used cannot be ground-referenced.  Unfortunately, the 3-lead LED does provide a ground reference, causing the unit to work erratically - if at all.

Swapping Data and Clock leads:

When Jacques originally designed the Compass rose, he simply used a software "bit-bang" function to receive the SPI data as the PIC he originally chose (the PIC16F628/A) does not have hardware SPI capability.  Because this new software does a lot of multiplexing of the LEDs, this approach could not work.

While the PIC that I use (the PIC16F819) does have a hardware SPI module, the pins used by Jacques do not map to the SPI inputs.  Rather than requiring a more complicated rewiring of the board, I was able to utilize Timer0 to receive the SPI clock signal - but this requires that the Data and Clock leads be swapped - a very simple modification.
 

Schematic showing the connection of the mode selector switch(es).
Click on image for a readable version

Mode selector switch:

The addition of a mode-select switch is highly recommended.  The ideal choice is a momentary, center-off SPDT switch - but these can sometimes be difficult to find.  (I used a CW Industries model GRS-4013C-0001 switch, available from Mouser Electronics.  This is a snap-in, square, black rocker switch.)  If you have too much difficulty finding a center-off momentary SPDT switch, an alternative is to use a pair of momentary SPST switches.  Note that the signal from pin 16 of the PIC is somewhat noise-sensitive, so it is best to locate the switch fairly close to the PIC itself - especially the 10k resistor in the case of the single SPDT switch version.  In the case of two SPST pushbutton configuration, it is best to minimize lead length as much as practical.

Note that mode changes are saved in EEPROM so they will be in effect the next time that power is applied.

Replacing the chip:

The final modification is quite simple:  Plug in the processor with the new software.  (You did use a socket, didn't you?)
 

Operation of the mode selector switch(es):

There are two positions of the switch(es):  The "+" position - closing the switch connected to V+ - or the "-" position - closing the switch connected to ground.

There are also three ways to operate the switch(es):

• Holding a button while applying power.
• During operation, a momentary contact.  The change takes effect the instant that the button is released.
• During operation, pressing and holding (for about 2 seconds) and then releasing. Note that the change takes effect after holding the button for the required amount of time.

Holding a button while applying power:

• + (plus) - Toggles the direction of the display (e.g. "flips" the display.)
• - (minus) - Toggles the enabling/disable of the average display

Pushing a button momentarily:

• + (plus) - Toggle between Dim and Bright display
• - (minus) - Clear the history (if enabled) and/or average (if enabled.)

Pushing and holding a button:

• + (plus) - Enable/disable history display (does not affect average)
• - (minus) - Toggle between running and sliding average (this resets the average.)

Comment:

Compass rose firmware versions prior to 19 July, 2005 had the "Dim/Bright" and "Enable/Disable History" button functions swapped, that is a momentary press enabled/disabled history while a "pressing-and-holding" toggled dim/bright.

The center LED:

In Jacques' original firmware, the only 2-color LED was the center LED:  This indicated red to show that the bearing was bad and green to show that the bearing was good.

In this firmware, the center LED blinks briefly along with the cardinal points and the color indicates one of several conditions:

If averaging is enabled:

• Red center LED:  This indicates that the compass rose in the running average mode.  In this mode, the average direction displayed is based on all bearings received since the unit was powered up or since the average was cleared.
• Green center LED:  This indicates that the compass rose is in the sliding average mode.  In this mode, the average direction displayed is based on the 16 most recent good bearings.

• Red center LED:  This indicates that the most recent bearing was "bad" (e.g. below the quality threshold setting.)
• Green center LED:  This indicates that the most recent bearing was "good" (e.g. at or above the quality threshold setting.)

• I couldn't think of anything else to do with the center LED:  If you have some ideas, let me know...

Other blinking LEDs:

The LEDs at the 4 cardinal points (North, South, East and West) dimly blink in unison with the center LED.  The North LED always blinks GREEN while the other three blink RED.  This is done so that one may visually orient the display in the dark.
 

Useful operational tips:

• When powered up, the compass display will "spin" two full revolutions (one red, then one green) in the direction of operation.  If the compass spins CLOCKWISE then the compass rose is in the normal mode.  If it spins COUNTER-CLOCKWISE upon power-up, the display is flipped from right-to-left. On power-up, the display always spins in the direction of increasing degrees!
• When in daylight, it's can be difficult to see the display - not to mention the dimmer "history" display, so it is probably best to shut off the history display anyway.  Doing so diverts more power to the direction/average LEDs and makes them noticeably brighter.  Turning off the average will make it slightly brighter, still - but since the average is so useful, you may not want to shut it off.
• Remember that the averaging only shows the proper bearing while you are stationary or traveling in a straight line.  If you turn a corner, the average built up so far becomes useless - especially if the compass rose is in the "running average" mode!  This is what the "Average Clear" function (momentarily pressing the "minus" button) is for!
• Until the first bearing comes from the DF unit, none of the LEDs may light up - other than those that are blinking.  This is particularly true if the firmware is configured to send the average bearing to the compass-rose display!  (Note that this only applies if you are using the alternate firmware.
• Using the Alternate firmware one may select whether the bearings sent to the compass rose are the integrated bearings or the averaged bearings. It is important to note that selecting these two sources causes the compass rose to behave differently, however:
• When integrated bearings are being sent to the compass rose, good bearings will display as green while bad bearings will display as red.  The threshold between "good" and "bad" is determined by the "QF" setting.  What this means is that even when there is no signal, or the signal is bad, you will still get direction indications.
• Averaged bearings, on the other hand, consist only of "good" integrated bearings.  For this reason, when the "good" integrated bearings stop, the average output stops being updated as well.  For this reason the compass rose will stop being updated when the input signal is of poor quality and/or if the signal goes away.  Note, however, that several "good" bearings together can comprise one "bad" averaged bearing:  An example of this would be if you got four "good" bearings - one each from the North, South, East and West.  Clearly, the average of these bearings is no direction at all and this result is "bad."
• When changing a mode that requires press-and-holding the button (e.g. turning averaging on/off or switching between running and sliding average) the feature changed by a momentary button press may occasionally be triggered as well (e.g. turning on/off the average may also switch between dim and bright.)  This has been traced to the "bounce" caused by some switches where they may make intermittent contact as they are released.  In testing, additional software "debouncing" was tried to prevent this, but this ruined the "feel" of the switch action.  In other words:  Just get used to it (or try a different switch.)  Remember not to put a capacitor across this switch or else it won't work at all!
• It is possible to drive more than one Compass Rose display board from a single DF unit, where the extra compass rose display was mounted in a location more easily seen than the one on the DF unit.  See the Outboard Compass Rose Display page for more info.
• Note:  The only information sent to the compass rose display pertaining to quality is that it is "Good" (equal to or above the "quality factor" threshold) or "Bad" (below this threshold.)  While the absolute quality could have been sent to the display, Jacques' original data format was preserved for compatibility.

• If you send the "current" bearing to the compass rose (the "INT" setting on the "ROSE" parameter) the averaged displayed on the compass rose in yellow is not the averaged bearing that you see on the LCD, but rather an averaged bearing calculated by the compass rose display itself based on the bearings that it receives.
• If you send the "averaged" bearing to the compass rose (the "AVG" setting on the "ROSE" parameter) the bearing displayed in green is the averaged bearing as shown on the LCD (and the "current" integrated-only bearing is not displayed on the LED compass rose at all) and that the "averaged" display on the LED compass rose (in yellow) is really an "average of the average."

• The "Invert Color" setting (see below) may have to be activated.  If the polarity is incorrect, one would see only "bad" readings with the single-color LEDs.
• Disabling "average" display.  With only one color, it may be difficult to tell the difference between the "average" and the "current" bearing - although the "average" will be slightly dimmer owing to the fact that it's yellow color is a mix of two colors.  Disabling the "average" will also cause the center LED to blink red or green if a bad or good bearing is being received, respectively.
• Only the "north" cardinal point LED will appear to blink.
  

The version number of the compass rose firmware is written directly on the chip itself.

Version "1R" (dated 20050323).  This was the first version to be released.

Version "1S" (dated 20050719).   Minor changes were made as noted:

• Selection options swapped:  A momentary press of the button to V+ will toggle between dim and bright while press-and-hold of the button to V+ will toggle enable/disable of the history display. 
  
• The brightness of the blinking cardinal points has been increased to make them more visible in the dark.
• A slight adjustment was made to make the "Average" LED appear more "Yellow" in color.

• Originally, the "averaged" bearing displayed was calculated based on the past 16 bearings received:  This average had nothing to do with the averaging done by the main Doppler unit.  This modification optionally allows the compass rose to receive the averaged bearing in addition to the "current" (integrated-only) bearing so that the bearing displayed on the LED compass rose matches what is shown on the LCD and is affected by the averaging settings of the main Doppler unit.  Note that this new function requires newer code in the main Doppler unit, but is backwards-compatible with earlier versions of the alternate firmware and is has been tested with a version of Jacques' original Doppler III code.The last "good" bearing is now frozen.
• Previously, the "good" bearings were shown in green and the "bad" bearings were shown in red - but the green "good" bearing disappeared as it was displaced by "bad" bearings.  Now, the last "good" (green) bearing remains if the unit starts displaying "bad" bearings - but the "bad" (red) bearings disappear when "good" (green) ones appear once again.  (Did that make any sense?)
• Modified blinking of cardinal points to have the same brightness but reduce duration of the blink itself.
  
• Minor tweaking to reduce the occasional corrupted data bit.  Once in a great while (one out of several thousand bearings) the compass rose would mis-read a bit sent over the serial stream.  It is extremely unlikely that the average user would have ever noticed this.
  
• Additional configurations/features.  These functions are "toggled" by grounding the specified pin through a resistor (a value from 220 to 1000 ohms) while the unit is powered up.  These settings are retained in nonvolatile memory and are thus "remembered.":  
• RB0 (pin 6) - Color Mix adjustment -  This toggles the color "mix" setting to make "yellow" between 25%-75% and 50%-50%.  Using the specified Liteon LED (see above) the best "non-red, non-green" color (called "yellow" - but it is really more of an amber hue) is obtained by using 75% green and 25% red.  There are other LEDs that may be used, however, that produce a good "yellow" using a 50%-50% mix of red and green.  Default = 75%green, 25% red.
  
• RB1 (pin 7) - Color inversion -  This toggles between "inverting" of color.  If, for some reason, you managed to put all 36 LEDs of the compass rose in backwards, this will save your having to resolder each of them as it exchanges red for green and vice-versa (including for the "yellow" mix.)  Note that this does not affect the center LED.  Default = Inversion is off (e.g. LEDs are assumed to be installed "backwards" from the original artwork.)
  
• RB2 (pin 8) - "Same LED Blink" - This toggles enable/disable of "Same LED" blink.  If enabled, this feature causes the color of the LED to alternate if more than one color is to be displayed on the same LED.  For example, an LED will alternate between Green and Yellow if the "current" and "averaged" bearing are on the same LED, it will alternate between Green and Red if the "current" and "bad" are on the same LED, and it will alternate between Yellow and Red if the "average" and "bad" are on the same LED.  Default = "Same LED Blink" is on.
  
• RB3 (pin 9) - Rotate display 180 degrees - This toggles "180 degree rotation" of the display.  If you have, for some reason, mounted the compass rose upside-down, this causes the displayed bearings to be rotated 180 degrees to accommodate this.  The "spinning" LEDs at power-up also indicate that this mode is active as they always start their spin from the "North" LED.  If you have an outboard compass rose that is likely to be mounted in different places, this feature (along with the addition of a switch to select it) might be useful.  Default = Display is not rotated.
  
• RB4 (pin 10) - Turn off "BAD" readings - This toggles suppression of "BAD" readings.  When active, "Bad" readings (in red) are completely suppressed and never displayed.  Default = "Bad" readings are displayed.
  
• RB5 (pin 11) - Fast/Slow Cardinal Point blinking - This toggles fast/slow cardinal point and center LED blinking.  Fast blink (default) is about twice-per-second while "slow" blink is about one blink every 1.5 seconds or so.  Default = "Fast" cardinal points/center LEDs are blinking.
  
• RB6 (pin 12) - Enable/Disable Cardinal Point blinking - This toggles enable/disable of cardinal point and center LED blinking.  This is used if, for some reason, the blinking of the cardinal points annoys you. Default = Cardinal point/center LEDs are blinking.
  
• RB7 (pin 13) - "Average" display disable - Disables reception of "Average" from the main Doppler unit if it has code that supports it (e.g. Version "7A" or newer of the "Alternate" firmware.)  This feature may also be used to take care of some (presently unknown) incompabitility with older code or, perhaps, Jacque's code.  If you simply want to prevent it from being displayed, or if you have multiple compass rose display units and want to prevent one or more of them from using the main unit's averaging while allowing it for other.  (If set to "disable" the compass rose display will base display the "current" (integrated) reading in green and show its internally-calculated average - if enabled - in yellow when the main Doppler unit is set to "BTH" [e.g. "Both"] under the "Rose" parameter.)  Default = Average display is enabled.
  

• On previous versions, the blinking of the center LED would change color to indicate whether or not the unit was in "Sliding Average" or "Running Average" mode, or if the average display was disabled, the center LED would blink green for good bearings and red for bad bearings.  With version 2F the LED only shows red and green to indicate bad or good bearings, respectively:  It is up to the user to determine, by observation, whether the averaging mode is "sliding average" or "running average."
• On previous versions, when the "Cardinal Point Blinking" was disabled using RB6 (pin 12) see above the center LED was never illuminated.  With version 2F, if cardinal point blinking is disabled the center LED will stay on continuously and indicate red for a bad bearing and green for a good bearing.  Note:  If you prefer to operate in this mode you may wish to adjust the value of the series resistor to adjust the brightness of the center LED to make it better-match the other LEDs.
  

On July 20, 2005, a number of corrections were made to the documentation, pertaining to the center LED and blinking cardinal point LEDs:  Sorry for any confusion.

AVAILABILITY:

For information about availability of this firmware, please go here.

If you plan to use this compass rose with the older Doppler II unit, you may have to make your own circuit board.  It has been reported that Jacques is willing to sell just the compass rose display board, but that the availability of these may be limited due to their being made as a pair with the companion main Doppler III board.

Disclaimer:

While the code used in the Doppler unit itself was originally based on that of the original Montreal Doppler II DF unit by Jacques Brodeur, VE2EMM, the code for this compass-rose display was not..  Because this work was my own and was not done with his involvement, Jacques cannot reasonably be asked to offer any support or assistance regarding its operation!

Although good faith efforts have been made to make certain that the operation of the hardware/firmware is as described, it is possible that "undocumented features" (bugs) may be present:  It is through testing, use, and feedback from the users that projects such as this may be improved, and the user is asked to be understanding of this fact.  This firmware is strictly intended only for non-commercial amateur-radio use and any other use is in violation of applicable laws.

Do you have any questions on this or other DF-related topics?  Go here.

KA7OEI - 20110505