Raspberry Pi 4 Model B (4GB) Wiring Guide/Advice

Hi all, have been following OpenHD for a while now and had to sign up as I received some equipment to get involved!

First of all, thank you to those who have posted so many helpful things for us newcomers. Many things I’ve been able to read and learn before even plugging anything in.

I ordered the following:

  • 2x Raspberry Pi 4 Model B
  • 2x 32GB Sandisk Extreme Micro SD Cards
  • 3x ASUS USB-AC56
  • 1x Raspberry Pi Camera V2.1 plus 300mm cable
  • Misc cables (Micro HDMI to HDMI, USB C for power, etc)

I couldn’t help myself and had to test it out as soon as I could. I downloaded the software image and flashed the two cards, plugged a USB-AC56 into each Pi, plugged the camera into one and the other into the TV and had an image. Too easy, honestly took longer to open all the packaging than it did to initially test everything.

Next day I thought about hooking up the second USB-AC56 to the ground end, and it worked, for all of three seconds of image before the screen went black. I believe this is either due to power limitations of the Pi USB ports or the USB hub I’m using is just rubbish (probably the second option, as this later worked fine with both USB-AC56s connected to the ground Pi via the supplied ASUS desk-mounts/USB-extensions).

Moving forward, away from the dinner-table-setup I need to build-up the air and ground ends. This means soldering, removing failure points (USB connectors, etc). I have a supply of Castle Creation 5v 10A BECs that I plan to use on both ends.

So, now I have a couple of questions regarding the wiring and connections. I have seen people soldering to previous Pi versions, but has anyone hooked up a 5v supply to the Pi4B to supply power to the Pi itself and obviously to provide a heftier supply to the USB ports… I’m needing to know what to solder to where. Does anyone have any images/documentation about this process?

I would assume I’d split the 5v from the BEC, one side going to the GPIO pins to power the Pi and the other set directly to the USB-AC56(s), and then connecting just the D+/D- from the USB-AC56 to the Pi (can the D+/D- of two wifi cards go to the same D+/D- pads on the Pi?).

On the air end I’d like to have everything soldered, but the ground end I think I might get away with USB plugs (secured with hot glue). Should I then pull apart my USB hub and supply 5v directly there?

Any feedback on this most welcome. Am also happy to document the builds as this would also likely answer questions from people using Pi4B(s) in future.

Cheers everyone, my project is ongoing and is already attracting attention from my employers (we manufacture autonomous fixed wing aircraft, full stack, designed our own hardware, software and aircraft!) looking forward to becoming a more active member here!

FYI, after receiving all this help. And sticking with it, I got the system working on the bench.

I picked up some of the 1mm thick maple air-end antennas, and some maple patch antennas for the ground end.

Used high quality components for power regulation, used good wire, shielded everything sensitive. And on the bench it looked great. Walking around the house, it looked great.

However mounting the system on an aircraft (RC Plane) and trying it real-world, albeit with default settings, I would get maybe 40 metres before video froze up and then maybe 50 metres when it’d go out completely. I then spent about three months trying to learn the settings, trying various different settings and frequencies, trying other peoples settings (with essentially the same hardware being used). Range never improved.

Took it to a different location, didn’t improve.

Swapped wifi cards around, didn’t improve.

Replaced all antennas, didn’t improve.

Replaced two of the three wifi cards, didn’t improve.

Tried three different OpenHD releases, and a whole new round of settings for each one. Didn’t improve.

In disbelief I went and watched videos of people flying 20km+ with very similar setups, just to reassure myself that it can work. Then went back to spending several hours each evening to checking and trying different settings, desoldering everything and rebuilding/rewiring everything. I changed wires, made wires shorter, even ended up buying two new Pi4 units ‘just in case’.

And guess what, after all that time effort and determination. The results I ended up with were fantastic, provided the air and ground units stayed within 30 metres of each other.

I honestly have no clue how people have managed to get past 1km. Even half that. It’s been a money pit for sure… The one project I didn’t cheap out on, and it’s been horrible!

So heads up to the new guys, the lack of information and support here definitely leads to a lack of results.

See you in six months when it bankrupts me!

Hello and thank you for sharing this story. From what I read you got proper bec‘s but never used them ?
Pretty sure your Problem is not enough power on eighter side of the System.

Are you able to come to the telegram group so we can solve your problem together ?

Also heads up, and sorry that you got no answer till today :slight_smile:

After thinking about your problem today something else came to my mind:
are you using usb3.0 for the ground connections? If yes this can lead to bad interference and prevent you from getting more range. Try USB2 instead.

I’m away from my system at the moment, but rest assured I am using the CC 10A BECs on both ends.

I just didn’t post anything further earlier due to there being a distinct lack of activity on the forums.

Further, everything is directly soldered that can be.

For the ASUS sticks I removed the USB plugs and connected the D-/D+ to the USB2 pads on the RaspberryPi.

On the ground unit I have two ASUS sticks, the D-/D+ of each go to the two USB2 ports (or pads), so each USB2 port is occupied by a wireless card.

The USB3 ports I use for a mouse, and to save video to a USB stick.

The air unit is the same, but with just one ASUS stick to one USB2 port, and obviously nothing connected to the USB3 ports.

Then 5v is distributed from the BECS.

On the ground unit, there are three pairs of wires (GND/VCC). First pair goes to the GPIO to power the SoC. Second pair goes to the first ASUS stick. Third pair to the second ASUS stick.

The air unit is powered much the same, but with with just the one ASUS stick.

No actual unreliable USB connections are used, except for the mouse and storage device on the ground unit.

All wires are as short as I could make them, twisted (GND and VCC, or D- and D+ pairs) and shielded with Scotch Electrical Shielding Tape.

The only removable connections are:

  • XT30 plugs been power source (either a 6S 10,000mAh on air side or 3S 5200mAh ground side)
  • Camera CSI cables
  • Antennas
  • MicroSD cards

After ranting yesterday, without making any changes. I managed to get almost satisfactory video out to 800m. This is absolutely my best result yet, and has slightly restored some faith that I might be are to get further one day.

I had considered I was just in a noisey environment, but taking multiple samples across the 2.4 and 5.8 frequency bands within a 50km radius suggested I was in a fairly quiet region (which makes sense as is quite rural). And my results have seemed to be on par in at least four different locations (several hundred km difference).

I’ll try to get on Telegram in future. And maybe update this thread with some photos, etc… so that you can be assured it’s not just bad soldering or whatever.

Hi I0gic. I am really new in this project and I wonder if you managed to fix you problem. Just curious how did you wire USB data? There is diagram how to wire PI3B+ but I can’t find for 4B. Thanks.

I soldered the D+/D- of one card to TP6 and TP10 the other to TP18 and TP19. I forget which TPs are D- or D+, but I’m going to re-build and re-wire the system again (into a different airframe) so I’ll try to remember to get photos of this and make a note of which TPs are which.

I also had problems with range at first, but it was because I messed the settings. Try Zero settings shared here:

except that I am using 5.8ghz and UseSTBC=N and UseLDPC=N
By the way, my Ground is Rasberry PI 4 B 8Gb with Tplink T4U plugged to USB 3.0 port directly and all this is powered by simple 3A UBEC connected to Pi via pins.
Air is Raspebbery PI Zero with same card, but at this end everything is soldered, except 3A UBEC is just plugged via pins. GND and 5V goes to card dirrectly from these pins too.
Video was still got at 1.9km range with 6db dipoles on both ends. Didn’t find what is max range yet.

I also noticed this in your description

what is this? If that is hard drive, it might consume lot of energy.

Just a 64GB USB memory stick.

Take some pictures of your setup and share, please. In particular your wiring and how you are powering things. Power is critical- especially running a 4b on the air side

You definetly went all out on the hardware! Good on you! But not all that many people run a 4b on the airside so not sure if that is somehow a player in your issues. A 4b is probably more thirsty for some amps. EDIT: just saw buried in there the 10amp bec part… Also you might be more prone to overheat issues…

For more timely response to issues get on the telegram group. Otherwise the pace of responses might be anemic like you have experienced.

Most important- dont give up. You have some quality hardware and there is no reason you shouldnt get much better results

Did you ever find out what was going on? Hooked up oscilloscope to 5v rail to look for noise?

Just purchased ASUS AC56 for air side, and Alfa AWUS036ACH for ground side. About to purchase 2x RPI 4B for this… concerned I may have the same issue. Any comments?