Google Ad

Project #009 - DakarOSD/Lynx RC Plane OSD - Page 7 - Calibration/Setup


These procedures & notes offer basic instruction as to the setup & calibration of the DakarOSD & Lynx.
They are based on DakarOSD firmware version 2.7b, and Lynx firmware version 2.0.

Firmware for DakarOSD Ver2.7b located here.
Firmware for Lynx Main PIC Ver2.0b located here.
Firmware for Lynx LCD PIC 10Mhz Version located here. My own English version here.

Not got a suitable PIC programmer? This is the type of programmer I have, purchased via Ebay (search for Microchip PIC Programmer):

Note: This page is a moving target and was partly created from translated Spanish instructions & my own notes/findings.
If you find anything missing or wrong then please let me know.


Have fun!




These instructions are for the field setup prior to flight and assume the DakarOSD/Lynx is fully calibrate/tested.

1. Position the Plane within a couple of metres of the basestation.
2. Power up the Plane and wait a few minutes till a satellite signal is obtained.
3. Press the D.HOME button on the DakarOSD to zero the Dakar parameters.
4. Power up the basestation and observe the LED on the Lynx, it should be lit.
5. Press and hold the L.HOME button (till the LED is lit) on the Lynx to reset the basestation co'ordinates.
6. Walk out 10 to 20 metres central to the flying area you intent to fly in. Now press and release the L.HOME button on the Lynx.
7. Orientate the antenna so that it points towards your plane (still 10 to 20 metres out).
8. Optional - Walk sideways from the 10 to 20 metre position and just check the antenna tracks you.

The system is now set up, you can fly.


The DakarOSD has 5 options for display, and to change from one to another requires assigning an analogue channel of the Radio Rx and hooking it up the the DakarOSD board. From then on, adjustment of the pot on  the Tx will change the OSD screen, as follows:

0.9mS - 1.16mS = Disable OSD
1.161mS - 1.42mS = Main OSD screen
1.421mS - 1.68mS = Max recorded parameters (max altitude, speed, distance)
1.681mS - 1.94mS = Waypoint screen
1.941mS - 2.2mS = GPS co'ordinates screen

On power up the OSD defaults to the Main OSD screen, so if you don't actually hook up an aux channel from your Receiver to the DakarOSD board then all you will get is the Main OSD screen.
If your RC radio does not have an analogue aux channel then you are stuck with the Main OSD screen.

Here is more explanation of the 5 screen modes:

First screen: OSD off.

Main OSD screen:
- Altitude in mtrs.
- Variometer and rate of ascent / descent rate in meters / second.
- Distance in meters.
- Distance to home.
- Direction to home.
- Speed over ground in kph.
- Number of satellites.
- Minutes of flight.

In the second line (if selected to display):
- Voltmeter 1:
- Instantaneous current consumption in mA.
- Cumulative current consumption in mA (great for knowing battery life).
- Voltmeter 2 / RSSI receiver RC.

Max recorded parameters (flight session):
- Maximum height achieved.
- Maximum distance achieved.
- Maximum speed achieved.

- Waypoint or point excursion destination. The arrow back home now tells us the right path to waypoints.

GPS co'ordinates:
- Current latitude and longitude coordinates of the plane.



The DakarOSD has a single pushbutton switch & 3off potentiometers on the PCB.

1off pushbutton for re-setting the OSD parameters. Herein known as D.HOME pushbutton.
1off potentiometer for adjusting the OSD video contrast. Herein known as D.VIDEO pot.
1off potentiometer span control of the RSSI signal. Herein known as D.SPAN pot.
1off potentiometer zero control of the RSSI signal. Herein known as D.ZERO pot.

Calibration / Settings:-
Black or white characters:
To switch between black or white characters (on a grey background), power up whilst holding down the button until the led comes on, then release.

Establish a waypoint:
Press & hold the button at any time for 5 secs until the led comes on to set a waypoint.

Calibration mode:
To enter calibration mode, power up and wait until "GPS DakarOSD V2.7 x Hz" is displayed and then press & hold the pushbutton until the LED flashes. The number of times you let it flash before releasing the button will determine which area of calibration/settings you want to change. Once it flashes the number of times you require simply release the button. As follows:-

TWICE (about 10 secs) - The display will show '0' satellites and from here on the analogue functions such as Voltmeters, RSSI, Ammeter etc. can be calibrated. In addition the multiplier for the mAH can be set.

THREE TIMES (about 15 secs) - Activation, deactivation of the entire 2nd line of parameters on the OSD, i.e. the analogue parameters line.

FOUR TIMES (about 20 secs) - Activation, deactivation of the Ammeter on the OSD.

FIVE TIMES (about 25 secs) - Activation, deactivation of the RSSI on the OSD.

SIX TIMES (about 30 secs) - Invert / non-invert of the RSSI parameter.


There are 3off pushbuttons, 3off potentiometers & 3off LEDs.

1off pushbutton for re-setting 'home' GPS co'ordinates for the basestation. Herein known as L.SET pushbutton.
1off pushbutton for setting / testing servo travel. Herein known as L.TEST pushbutton.
1off pushbutton for alternating the screen on the LCD. Herein known as L.VID pushbutton.
1off potentiometer for optimizing the video signal. Herein known as L.VIDEO pot.
1off potentiometer span control of the servo travel. Herein known as L.SPAN pot.
1off potentiometer tilt control of the servo travel. Herein known as L.TILT pot.

Calibration / Settings:-
When the Lynx is powered up for the first time it is necessary to store which type of PAN servo you have fitted, i.e. 90deg, 180deg or 360deg type.
Note: In order to use the servo setting / testing facilities you must have a functioning video signal, i.e. valid GPS data from DakarOSD to Lynx.

On powering up the Lynx the VID LED will flash, and the number of times determining which type of servo is fitted.
1 flash = 360deg type servo.
2 flashes = 180deg type servo.
3 flash = 90deg type servo.
To change this, hold the L.TEST pushbutton down whilst powering up the Lynx. The VID LED will flash.
If you require 360deg type servo then let it flash once then release the L.TEST pushbutton immediately.
If you require 180deg type servo then let it flash twice then release the L.TEST pushbutton immediately.
If you require 90deg type servo then let it flash three times then release the L.TEST pushbutton immediately.

To calibrate the PAN servo travel, then power up the Lynx normally then press and hold the L.TEST pushbutton. The PAN servo will travel fully in one direction. If you then release the L.TEST pushbutton the press it again then the PAN servo will travel in the opposite direction. You can repeat this over and over to swing the PAN servo one way then the other.
So, whilst doing this you can adjust the L.SPAN potentiometer to fine tune the full scale deflection of the servo.

The TILT servo requires similar adjustment. When you operate the L.TEST pushbutton for the PAN servo calibration as above then in actual fact the TILT servo will operate also, swinging from fully up to fully down as you press the L.TEST pushbutton.
So, whilst doing this you can adjust the L.TILT potentiometer to fine tune the full scale deflection of the servo.
The TILT servo uses a 90deg servo. It is important that when the servo is fully down then it is completely vertical, and when fully up it is completely horizontal.

The L.VIDEO pot is necessary to optimize the reception of the data that is embedded in the video signal.
With the DakarOSD & Lynx powered up, and GPS data being received then adjust the L.VIDEO pot till the VID LED on the Lynx turns on. There will be a fine band where it's is almost on continously, and either side of that where it will be flickering or offcompletely. You are looking to have the LED as full on as can be. This maximizes the data being received.

The 2*16 LCD is controlled by a dedicated pushbutton. On power up it will display the welcome screen, and when NMEA data starts being received the VID LED will illuminate permanently and the LCD will automatically display the live GPS co'ordinates.
Pressing the L.LCD pushbutton will rotate the display around 3 different screens, as follows:

GPS co'ordinates:

No. of Satellites & Altitude:

Speed & Heading:

Please note that since these photos I have hacked the HEX file a wee bit and modified the text to English. It's available for download.