DragonOSD+ calibration procedures
Posted: Fri 16 Apr 16 2010 9:59 am
RSSI Calibration
For those wishing to calibrate their RSSI, the procedure is as follows:-
1. Make sure that RSSI is connected and you have some functionality
2. Turn the transmitter off
3. Adjust the RSSILOW parameter until the RSSI reading just reaches 0%
4. Turn the transmitter on (near the receiver)
5. Adjust the RSSIHIGH parameter until the RSSI reading just reaches 100%
6. Save the settings to EEPROM when you are satisfied with the results
Some notes about this:-
1. There will be some fluctuation of the RSSI reading so it's not unusual to see the readings jump between 0% to 7% on the low side for example. The high side values tend to be more stable but then again, do not be surprised at some fluctuation.
2. The RSSI reading is actually a voltage reading so that you can actually measure the RSSI line with a DMM to get an idea of what the voltages are. This way you can enter the voltages directly rather than take a trial and error approach to find the threshold readings. Having said that, it is probably still necessary to tweak it a bit to get the readings exactly right because the calibration of the board voltage readings may not be as accurate as that of your meter (or vice versa).
3. When using the menu to make this adjustment, it is necessary to exit the menu to look at the resultant readings. When using the serial terminal to make this adjustment, you should be able to see the change immediately. The serial commands take the form of:-
SET RSSILOW 1.0
SET RSSIHIGH 2.8
SAVE
4. All of the above assumes that you have already activated the RSSI percentage display. This would be the G.P. Input mode 2, which can also be set using the serial terminal command:-
SET GPMODE 2
Some of you may notice that there is a GPMODE 3. I do not recommend using this (dBm display) because you will need to calibrate this very accurately for it to make any real sense at all.
5. It should be fairly common knowledge at this point that some receivers will require a buffer for the RSSI line. The reason for this is three fold:-
a) the RSSI voltage is used for internal AGC (gain control) purposes of the receiver
b) it was not really meant to drive an external ADC (such as found on the OSD)
c) because of a & b, the RSSI voltage may be pulled too low and cause the receiver to malfunction
Some receivers such the the DragonLink do not have this problem but many of the other receivers do. If you need such a buffer, you can try the following link:-
http://www.dpcav.com/xcart/product.php? ... ge=14&js=n
6. Different receivers will require different calibrations, even if they're the same model and make.
7. For those of you who are planning to fly long range, I would suggest not going below about 30% to be on the safe side, unless you are equipped with a functioning RTH system.
Daniel
For those wishing to calibrate their RSSI, the procedure is as follows:-
1. Make sure that RSSI is connected and you have some functionality
2. Turn the transmitter off
3. Adjust the RSSILOW parameter until the RSSI reading just reaches 0%
4. Turn the transmitter on (near the receiver)
5. Adjust the RSSIHIGH parameter until the RSSI reading just reaches 100%
6. Save the settings to EEPROM when you are satisfied with the results
Some notes about this:-
1. There will be some fluctuation of the RSSI reading so it's not unusual to see the readings jump between 0% to 7% on the low side for example. The high side values tend to be more stable but then again, do not be surprised at some fluctuation.
2. The RSSI reading is actually a voltage reading so that you can actually measure the RSSI line with a DMM to get an idea of what the voltages are. This way you can enter the voltages directly rather than take a trial and error approach to find the threshold readings. Having said that, it is probably still necessary to tweak it a bit to get the readings exactly right because the calibration of the board voltage readings may not be as accurate as that of your meter (or vice versa).
3. When using the menu to make this adjustment, it is necessary to exit the menu to look at the resultant readings. When using the serial terminal to make this adjustment, you should be able to see the change immediately. The serial commands take the form of:-
SET RSSILOW 1.0
SET RSSIHIGH 2.8
SAVE
4. All of the above assumes that you have already activated the RSSI percentage display. This would be the G.P. Input mode 2, which can also be set using the serial terminal command:-
SET GPMODE 2
Some of you may notice that there is a GPMODE 3. I do not recommend using this (dBm display) because you will need to calibrate this very accurately for it to make any real sense at all.
5. It should be fairly common knowledge at this point that some receivers will require a buffer for the RSSI line. The reason for this is three fold:-
a) the RSSI voltage is used for internal AGC (gain control) purposes of the receiver
b) it was not really meant to drive an external ADC (such as found on the OSD)
c) because of a & b, the RSSI voltage may be pulled too low and cause the receiver to malfunction
Some receivers such the the DragonLink do not have this problem but many of the other receivers do. If you need such a buffer, you can try the following link:-
http://www.dpcav.com/xcart/product.php? ... ge=14&js=n
6. Different receivers will require different calibrations, even if they're the same model and make.
7. For those of you who are planning to fly long range, I would suggest not going below about 30% to be on the safe side, unless you are equipped with a functioning RTH system.
Daniel