DJI has released its 2.4G Full HD digital video downlink, the DJI Lightbridge
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1. No but they could use a 5.8gHz or UHF unit and a LB Ground Station set to slave mode..
2. No and that has been stated from the very beginning that you loose the ability to do 360 pans.
3. Possible. I have one user that is connecting the Lightbridge to the gimbal and then using UHF for RC control. His FPV is 5.8gHz.
flitelab
Member
They don't at present have them available stand alone that I have seen listed for sale. Only the 2.4 system is separate item so far.
econfly
Member
OK (speaking of DJI 5.8GHz radios here) -- but obviously nobody is going to buy an FC40, tear the receiver out of it, and than transplant it into their two-man setup to control the gimbal. At this point, I think it's fair to say that DJI doesn't sell a 5.8GHz solution as they diagrammed it in their post today.
flitelab
Member
Exactly. Right now there is no solution to make it function as advertised. last I heard you cannot even use the mapping from the A2 as was noted they did in the demo video with the GH3. You need to have a new BMPCC Zenmuse for dual operator setup.
econfly
Member
There are three issues here, all unrelated, for current WKM/A2 and Zenmuse users.
1. Standard (AV) video in: You need to make your own cable or wait for the cable announced today. HD is off the table without an HDMI connection directly to the camera.
2. Power and OSD info in: Again, you need to make your own cable or wait.
3. Radio control of the Zenmuse: Open question. For a one-man setup you would need an A2 (and its four control outputs -- one of which is going to be gear for most of us, leaving 3 Zenmuse channels). For WKM users or to get more than the four channels from an A2 the option is to use a y-cable out of the air unit's DBUS port, one output to the WKM/A2 and another to an S.Bus decoder. For the decoder you take standard PWM channels to the Zenmuse. I will confirm (or not) that this works later today.
For a two-man setup, I have no idea. You do have the tethered option on the ground (don't know if this actually works, or how). For two untethered ground radios -- and this has nothing to do with your gimbal or anything related to (1) and (2) above -- you need a receiver dedicated to the gimbal. We do this now and it works just fine. The problem introduced formally for the first time today is that DJI is telling us not to use 2.4GHz for the gimbal receiver. But they don't offer an alternative (despite the implications of their diagram). One would need to find a radio/receiver setup that does not interfere with 2.4GHz. I haven't looked to see what's out there. Maybe this is easy -- I don't know. What I do know is that I was using two 2.4GHz receivers for a two-man setup and now that won't work if I move the flight radio/receiver to the Lightbridge.
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econfly
Member
As I understand it, that's correct for tethered ground use (apparently that only works with a new "HD" gimbal control unit, and that's only rumored to be coming out for the BMPCC Zenmuse). I agree that the marketing was completely misleading on this point, and clearly indicated that tethered ground use was possible without limitation regarding your gimbal (I don't understand any of this yet -- why the gimbal port is related is beyond me; I'll try to figure it out).
For untethered ground use you will have options, but they require an air receiver dedicated to gimbal control that operates with a ground radio at some frequency that won't interfere with 2.8GHz. DJI recommends a 5.8GHz radio/receiver pair for this, but they don't sell such a combination. I don't know if anyone does -- anybody know anything about 5.8GHz rc control?
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econfly
Member
OK DJI experts, I have one very simple and extremely important question:
HOW MANY CHANNELS CAN LIGHTBRIDGE TRANSMIT FROM A SINGLE RADIO?
I've been banging my head against the wall for an hour and if I'm right (and I hope I'm not) this thing will only function if the Futaba radio has the trainer port in 8 channel mode. The Futaba T14SG can output 8, 12 or 16 channels over the trainer port, but it's only working for me if I set it to 8.
EIGHT
We were promised 16 channels. And my sinking suspicion is that 16 = 8 + 8, and only works in a tethered two-man setup where each radio outputs, at most, 8 channels.
Tell me I'm wrong. Really, I would love to be wrong about this.
HOW MANY CHANNELS CAN LIGHTBRIDGE TRANSMIT FROM A SINGLE RADIO?
I've been banging my head against the wall for an hour and if I'm right (and I hope I'm not) this thing will only function if the Futaba radio has the trainer port in 8 channel mode. The Futaba T14SG can output 8, 12 or 16 channels over the trainer port, but it's only working for me if I set it to 8.
EIGHT
We were promised 16 channels. And my sinking suspicion is that 16 = 8 + 8, and only works in a tethered two-man setup where each radio outputs, at most, 8 channels.
Tell me I'm wrong. Really, I would love to be wrong about this.
This was from the prerelease information in January. Built-in Remote Control Link
-Uplink remote control transmission and downlink video work simultaneously on 2.4GHz.
-Remote control data travels to the uplink via the TX-Thru Port at the same time that video is streamed back down all without interference.
-Support for two remote controls: one for flight control (10 Channels) and the other for gimbal control (6 Channels). Control signals are received in the air and then transmitted to the flight controller through D-BUS.
-When used with a non-2.4G radio transmitter, video only transmission operation is supported. The DJI 5.8G radio transmitter is recommended.
I don't know if the specs changed since that time. I will check and let you know.
-Uplink remote control transmission and downlink video work simultaneously on 2.4GHz.
-Remote control data travels to the uplink via the TX-Thru Port at the same time that video is streamed back down all without interference.
-Support for two remote controls: one for flight control (10 Channels) and the other for gimbal control (6 Channels). Control signals are received in the air and then transmitted to the flight controller through D-BUS.
-When used with a non-2.4G radio transmitter, video only transmission operation is supported. The DJI 5.8G radio transmitter is recommended.
I don't know if the specs changed since that time. I will check and let you know.
Quote:
IMPORTANT NOTE:
Use your own 2.4G radio to control your multi-rotor via Light Bridge, and DJI 5.8G radio to control directly the Zenmuse gimbal. Never use 2.4G radio for gimbal control since it will interfere Light Bridge.
Have DJI released a piece of equipment that is prone to interference from 2.4G Radios? What happens when somebody else switches on their 2.4G radio at the flying field or any where else for that matter?
I understand that the Light Bridge could swamp an onboard 2.4G RX hence why we should use the command link but to state that a 2.4G TX source will 'Interfere' with the Light Bridge is disconcerting to say the least.
IMPORTANT NOTE:
Use your own 2.4G radio to control your multi-rotor via Light Bridge, and DJI 5.8G radio to control directly the Zenmuse gimbal. Never use 2.4G radio for gimbal control since it will interfere Light Bridge.
Have DJI released a piece of equipment that is prone to interference from 2.4G Radios? What happens when somebody else switches on their 2.4G radio at the flying field or any where else for that matter?
I understand that the Light Bridge could swamp an onboard 2.4G RX hence why we should use the command link but to state that a 2.4G TX source will 'Interfere' with the Light Bridge is disconcerting to say the least.
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econfly
Member
Thanks. I have learned more -- spent the past hour or so running the system and looking at S.Bus to PWM converter output on the oscilloscope. Here is what I know so far:
(1) The input to the Lightbridge ground unit accepts a Y cable with the ability to connect to two radios. This works just fine. On the air side, the PWM signals from the pair of radios is encoded into S.Bus and output through a single two-conductor cable.
(2) Air side S.Bus (DJI calls it DBUS) encoding is standard and you can decode it with a Futaba SBD-1 S.Bus decoder. This means you can use the Lightbridge with any system, controller, servo, or gimbal that can accept S.Bus or PWM. To get PWM you just need an air-side S.Bus decoder with PWM output. The only limitation is that you don't get OSD video overlay without a DJI controller. To be clear, on the control side this system has no limitations that require a DJI flight controller or gimbal. All channels are accessible over standard S.Bus and any of the 16 channels can be converted to the usual PWM output and simply plugged into anything that accepts PWM.
(3) The first radio (red plug on the ground side) is encoded into the S.Bus stream with channels 1 through 8 on the radio side matching channels 1-8 on the air S.Bus. The second radio is encoded with channels 1-8 mapped to 9-16 on the air side S.Bus. You cannot assign higher channels on either radio. The trainer port must be set to 8 channel output. Each radio is effectively an 8-channel radio. A single radio operator has 8 channels -- no more.
So, as you guys have been trying these out over the past few months, has anyone tried to map a channel in the A2 higher than 8? Or have you tried setting your radio trainer port to anything other than 8 channels? I can't believe I'm the first guy to notice this, and that makes me think I am wrong about something. However, having spent the evening playing with the control output and looking carefully at channel mapping on an oscilloscope, I am confident the above listed results are correct. What I am hoping is that somehow I am missing something with the trainer port to Lightbridge connection -- that maybe there is a setting on the radio, for example, that will allow more than 8 channels. So far, all I can get to work is the function described above.
FYI to anyone following this: With minimal documentation and only a few hours working with this I am learning in real time with plenty of uncertainty involved. My views may change as I learn more.
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econfly
Member
That's good to know. A few questions if you don't mind:
1) Do any of your mapped channels above 8 actually do anything? That is, do you see reaction in the A2 assistant when you change channel 9 or higher on the radio?
2) What is the setting on your Futaba radio for the trainer port number of channels (System->Trainer, page 4)?
I just hooked up the Lightbridge to my A2 and I get the same result as before. No RC signal at all is received if the trainer port on my T14SG is at anything other then 8 channels. And, in that mode channels 1-8 work fine, but I can't get any reaction for a channel number greater than 8 in a single-radio setup (I can map them but they do nothing).
Thanks for all of your help. Without you guys we would really be in the dark here.
flitelab
Member
So 4k is a no go? I believe the gh4 outputs the same as it is set to record in so sounds like this is another issue.