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Tello PCB and antenna reference, to help fellow crazy modders ;)

Customerx

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The esp8622 can't handle the TELLO data at all. Waiting for the ESP32 to see if any better.
 

ph2t

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Thanks ph2t! Very detailed and informative post. Can you tell me how to remove the rubber part of the leg? I need to solder back the wire that came off the antenna after a crash.
thanks iHello. I used a Stanley knife (aka sharp hobby knife) to cut the rubber feet off. The front ones come off easily but the rear ones you will need to cut around the PCB antenna that is within the rubber foot. This is a destructive method of getting the feet off unfortunately, you can't use them again. They are glued so maybe you can put the foot over the steam from a boiling kettle - that may loosen the glue somewhat to allow you to remove the feet without cutting.

cheers,
ph2t.
 

iHello

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thanks iHello. I used a Stanley knife (aka sharp hobby knife) to cut the rubber feet off. The front ones come off easily but the rear ones you will need to cut around the PCB antenna that is within the rubber foot. This is a destructive method of getting the feet off unfortunately, you can't use them again. They are glued so maybe you can put the foot over the steam from a boiling kettle - that may loosen the glue somewhat to allow you to remove the feet without cutting.

cheers,
ph2t.

Thanks ph2t. I managed to remove the feet.
 

junkyardog187

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I've been working on a few mods that have required me to gut my poor tello several times over. I have put together a couple of pictures that have helped me with my modding. Motor and antenna pinouts, etc.

I'm doing some more research into the tello antenna configuration and will post on that here as well. Write-ups take time, especially when you want to lay a lot of information out in a way that helps others. Please be patient with me as I add my thoughts and results to this thread. ;)

Tello printed circuit board (PCB) layout - viewed from the underside.

View attachment 2605
Notes on the above picture:
  • The antenna is approx. 10mm in length, at 2.4GHz this puts it at less 1/10th of the wavelength of the Wi-Fi signal. An antennas length is guided by wavelength of the signal it is carrying. Wavelength is to do with frequency. I won't go into it here, google "wavelength and antennas" to get the gist. The diagram above quotes 1/4 wavelength, this is incorrect.
Tello antenna PCB - located in the two rear motor mounts.
View attachment 2606


Notes on the above picture:
  • The tello has two independent antennas that are not directly connected
    • According to other forum posts here it is a smart antenna array (two antennas located in each rear motor mount) that dynamically changes between each antenna depending on which one has the better signal connection to the smartphone controlling it.
    • The antennas are patch antennas, a flat antenna that is etched onto a PCB. Usually the ground plane is located on the other side of the PCB - in case of the tello the circular coil located above the antenna is the ground plane.
  • The antenna is approx. 10mm in length, at 2.4GHz this puts it at less 1/10th of the wavelength of the Wi-Fi signal. An antennas length is guided by wavelength of the signal it is carrying. Wavelength is to do with frequency. I won't go into it here, google "wavelength and antennas" to get the gist.
  • Antennas under a 1/2 wavelength generally perform better when provided with a ground plane (old engineering degree notes here, I might be wrong). The coil shaped wire in the above picture is providing the ground plane for the small antenna that is on the PCB.
  • All the transmitting and receiving for the tello is done through its two rear feet, not the arms nor the chassis.
More to come... Just getting this up for the moment and I'll edit/contribute more as a test and confirm my theories.
cheers,
ph2t.
Thank you a lot do you recommend buying Bluetooth control
 

SleepyRobo

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Thanks ph2t! Very detailed and informative post. Can you tell me how to remove the rubber part of the leg? I need to solder back the wire that came off the antenna after a crash.
They are just glued on, just take a pic and start paying they will come off, there is a cavity for the antennas to sit in.
 

SleepyRobo

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Thank you a lot do you recommend buying Bluetooth control
So Bluetooth runs on 2.4ghz and wifi runs on 2.4ghz now they are different wave lengths when you look I to it, but the last time I tried Bluetooth controller with Tello the lag was unbearable, now some say a wifi repeater like the xaiomi repeater 2 helps to fix that but it can still be an issue. I use the Moto z gamepad mod direct connection but any USB otg controller that has it's own battery power should work, some phones cant send power and USB data over it's charging port when otg used.
 

SleepyRobo

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The esp8622 can't handle the TELLO data at all. Waiting for the ESP32 to see if any better.
So the Tello broadcasts a signal that only a MU-MIMO repeater can receive in the case for you. This is why the Xiaomi wifi extender 2 is so highly recommended, it uses this technology of communication. Your phone is also capable of this in a way of receiving such signal. The esp8622 does not support this architecture.
 

ph2t

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I think the best way to try out different antennas on this tello chassis would be to introduce a set of U.FL sockets onto the tello PCB where the original antenna cables were soldered.

From the picture in the first post of this thread, here are the antenna pads highlighted.

IMG_4508.JPG

I'm going to try and mount two U.FL sockets here. They look like this:

U.FL-R-SMT(01).jpg

Having these U.FL connectors installed will allow me to swap out different antennas easily.

I have ordered the goods and hopefully in the next week I will have this mod done and ready to try out!
 

TonyC

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Customerx

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So the Tello broadcasts a signal that only a MU-MIMO repeater can receive in the case for you. This is why the Xiaomi wifi extender 2 is so highly recommended, it uses this technology of communication. Your phone is also capable of this in a way of receiving such signal. The esp8622 does not support this architecture.
Just to clarify when using the esp8266 I'm connecting through the Xiaomi then to the TELLO. In case of confusion.
 

bapp1236

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I think the best way to try out different antennas on this tello chassis would be to introduce a set of U.FL sockets onto the tello PCB where the original antenna cables were soldered.

From the picture in the first post of this thread, here are the antenna pads highlighted.

View attachment 3506

I'm going to try and mount two U.FL sockets here. They look like this:

View attachment 3507

Having these U.FL connectors installed will allow me to swap out different antennas easily.

I have ordered the goods and hopefully in the next week I will have this mod done and ready to try out!
Have you tried a true 1/4 wave dipole antenna?
 

bapp1236

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I had a 4Hawks panel antenna laying around and I took the board out of the Mi extender, added SMA connectors to the board, put everything in a project box, and I can get out almost 1/2 mile with no mods to the aircraft.
 

NeilA

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I've been working on a few mods that have required me to gut my poor tello several times over. I have put together a couple of pictures that have helped me with my modding. Motor and antenna pinouts, etc.

I'm doing some more research into the tello antenna configuration and will post on that here as well. Write-ups take time, especially when you want to lay a lot of information out in a way that helps others. Please be patient with me as I add my thoughts and results to this thread. ;)

Tello printed circuit board (PCB) layout - viewed from the underside.

View attachment 2605
Notes on the above picture:
  • The antenna is approx. 10mm in length, at 2.4GHz this puts it at less 1/10th of the wavelength of the Wi-Fi signal. An antennas length is guided by wavelength of the signal it is carrying. Wavelength is to do with frequency. I won't go into it here, google "wavelength and antennas" to get the gist. The diagram above quotes 1/4 wavelength, this is incorrect.

Tello antenna PCB - located in the two rear motor mounts.
View attachment 2606


Notes on the above picture:
  • The tello has two independent antennas that are not directly connected
    • According to other forum posts here it is a smart antenna array (two antennas located in each rear motor mount) that dynamically changes between each antenna depending on which one has the better signal connection to the smartphone controlling it.
    • The antennas are patch antennas, a flat antenna that is etched onto a PCB. Usually the ground plane is located on the other side of the PCB - in case of the tello the circular coil located above the antenna is the ground plane.
  • The antenna is approx. 10mm in length, at 2.4GHz this puts it at less 1/10th of the wavelength of the Wi-Fi signal. An antennas length is guided by wavelength of the signal it is carrying. Wavelength is to do with frequency. I won't go into it here, google "wavelength and antennas" to get the gist.
  • Antennas under a 1/2 wavelength generally perform better when provided with a ground plane (old engineering degree notes here, I might be wrong). The coil shaped wire in the above picture is providing the ground plane for the small antenna that is on the PCB.
  • All the transmitting and receiving for the tello is done through its two rear feet, not the arms nor the chassis.

More to come... Just getting this up for the moment and I'll edit/contribute more as a test and confirm my theories.
cheers,
ph2t.
Really liking your post, that just saved me from tearing down my own tello out of sheer interest. :)

I notice what looks a bit like a ufl-connector next to the power-button.
1568901571626.png
Any chance that it would be possible to hook up an antenna like this to it you think?
 

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