What are the advamtages of using a rpi and connecting all the sensors compared to using the already available flight controllers with appropriate sensors already installed?
Is it kind of like saying “cars are too expensive why cant i just get an engine and attach some wheels and put some seats on it and a roof and some doors”?
On a Pi Zero, nothing so far as I can tell. The specs are attractive, but you can’t compare that directly to something like an STM32 unless you compile a custom OS for it. By the time you add all the layers of complexity of a fully fledged Linux OS and layer ArduPilot for Linux on top of it, it becomes an anemic, ill suited bit of kit. The built in companion features will likely run slowly/poorly, if at all.
Good question! I was searching for a flight controller and found the PXFMini (Which is now unavailable) I found the form factor clever and the feature OK for my use case. It was simply ArduPilot on a Raspberry Pi it could have been anything. But I still needed to add at least a GPS and a magnetometer, to have autonomous flight.
I went the Raspberry Pi way for two main reasons. The first one is outside of ardupilot, I think it makes a great all-in-one cape for all it’s sensor and PWM output. The second one is for future feature addition, for now I would like to have Ardupilot running only (At least on a pi zero) then add feature such as a video feed, ROS2 or other probably not on a Pi Zero, maybe a Pi Zero 2 or other Pi derivative. This is the main reasons of why I wanted to use a Raspberry Pi instead of a STM32.
I taught about making a complete Ardupilot-as-cape for Raspberry Pi. That would make a complete Flight controller, with the possibility to communicate with Ardupilot. Do you think that would be a better solution? You can add a Raspberry Pi if you want, or use the cape without it. That would make for a compact solution without all the linux work, what do you think about that?
Thank you for your input, it’s really appreciated
I agree with you, what I would like in an ideal world is a fast linux computer that could run ardupilot and some other software. And I really think the Raspberry Pi Zero W is ill suited for this. My plan is to be incremental, starting with a pi zero and running ardupilot only, then try to add features if possible. My real target is a Pi Zero 2W but I cannot get one, since the PXFMini is able to run Ardupilot, I was hoping that a more powerfull quad-core Pi Zero 2 would be able to run at least ardupilot with some other software. Do you have any experience with other linux boards, or some things I could leverage from? I Will try to check the usage of the board with the raspberry pi running Ardupilot on a Pi zero and an Pi 3 that i currently have, that will give me an idea of what I have to work with.
I used Yocto to build my Custom Linux OS, it is working fine the setup is not yet complete but as a proof of concept it works allright, I built the core-image-minimal, with the I2C, SPI and UART enable, with the device tree for the UART Expander. Then I add ardupilot manually. It starts and evertything seems fine, I have yet to actually use the device, in a vehicle. I will try to do some benchmarking with this OS as well. I have not tried this, but I can make some CPU realtime, and pin a task to it, i think that is something worth looking into.
Do you think a Pi Zero running Ardupilot will work? And let’s say a more powerfull Pi (3, 4, Zero 2W) do you think it would be able to run some other software?
Thank you for your input, it’s really appreciated!
When I said Pi Zero, I meant any flavor of it. I also think a 3B will likely prove inadequate if you intend to run additional companion software. I have been woefully unimpressed with the BeagleBone Blue, and this is just an attempt to reinvent that wheel.
For the same $150 pricetag, I could get a proven H7 based autopilot plus a Pi Zero as a dedicated companion with far fewer headaches.
On the other hand, if I wanted an underpowered, all-in-one Linux solution, I could spend a mere $40 on a BeagleBone Blue.
I haven’t tried to use the beaglebone blue, the specs seems really similar to a Raspberry Pi Zero, which indeed would make it underpowered. I was thinking of using a Raspberry Pi as it was more accessible but a STM32 H7 with the same form factor as pi zero would work without needing to run Ardupilot on a Linux device.
The thing I liked about my solution was that it was all in one you only needed to add the receiver, and ESCs with the possibility to add a RFD900 for example instead of using wifi for telemetry. Are you aware of such a flight controller that is pretty much complete? The closest I saw was the Navio2.
Now I’m confused. Every autopilot with which I’m familiar simply requires a receiver and ESCs, with GPS and telemetry optional, as desired…
I really don’t understand the draw to your proposed solution.
To be blunt, a Pi hat is a rinky-dink, half-assed solution to a problem that doesn’t exist.
I can see the confusion, in my head it’s clear but in writing it definitely is not… I will try to makes things clearer, tell me if it helps!
What I want and it is a stretch is a drone Flight Controller like a DJI flight controller, I would only need to add a battery to the ESC, the BEC would power the ESC and that’s it an autonomous fronted ready to fly. I also would have like to have a video stream live that’s where the raspberry pi in my original idea came from. I like my drone to be clean and small and I could never achieve that using the pixhawk cube, there is wire everywhere like a lot. There is one for the gps, one for the RFD900, the power module, another one for the companion computer, the buzzer safety switch, receiver. And I think a lot of these could be integrated into the flight controller itself to make for a clean and light flight controller. To give you an idea of what I am used to in term of drone that is the page of the group of drone I was in, there is some picture of the hexacopter I worked on VAMUdeS - Véhicule Aérien Miniature de l’Université de Sherbrooke it is in French but you just need to look at the pictures you will see what I means by a mess of wire!
I really feel like a lot of parts that are external now gps, buzzer, status LED, safety switch could easily be integrated into a flight controller PCB which would reduce weight, and complexity for new users and would make for lighter builds where drone weight is restricted like in Canada where I live it’s 250g maximum without a licence.
Is what I am trying to achieve clearer? I want you to be blunt, my experience is not the same as everyone else if there is need or want for what I’m trying to build then great otherwise I will modify it or not do it at all!
Many of Matek’s autopilots include a minimal BEC that has multiple regulators for various peripherals. Skip the LEDs and buzzers in favor of passthrough telemetry for status indications. Add a small, digital FPV VTX and camera, and you’re in business without the overhead of a Linux computer at all.
If you’re dead set on a companion, add some variant of a Pi Zero to the mix and leverage its full power for peripheral tasks rather than relying upon it for flight critical processing as well. At ~10g, it isn’t much of a burden.
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I am really not dead set on a pi, or any companion I wanted to use the Pi to be able to add features down the road, I think you are right to use a STM32 with all the needed hardware for autonomous flight is more reliable without Linux over head and related issues.
As for the FPV VTX I am really new to that world and don’t know a lot, I will look into available module for HD VTX if any, I am not sure if I would be able to “make” it myself without a module, I am a computer engineer that can make some PCB, but mostly I write firmware.
I really appreciate that you took time to read and answered my post!
Thank you
The Kakute H7 Mini can be had with a small 4-in-1 ESC that is somewhat purpose built to accept a VTX as well. It’s light and fairly full featured. Worth a look for your application.
Keep in mind a lot of those components require some separation to work properly without interference. Where companies have made single-board custom flight controllers with all those things combined they probably spent 9873764587126398734.73 man-hours designing and testing the board.
Particularly the GPS and compass need separation from everything else, and will be almost useless onboard. In probably 90 percent of cases or more we disable the onboard compass, or at least move it down the list and prefer the external compass in the GPS case.
Also you can cut down on some items. Like use a receiver and transmitter combo that does the RC control and telemetry in one. There’s more than one option depending on what level of telemetry you need. See yaapu telemtry that runs on a compatible transmitter - that is enough in a lot of cases.
If you need long range you can use an RFD900 TXMOD combo for RC and telemtry (+ wifi to laptop) but that does punch a hole through the budget.
I have to agree with you here, the thing that worries me the most is the magnetometer, which as you said is mostly unused in favor of external ones. And I am no PCB design expert, I can make a working board bu not necessarily a perfect one. Do you think, or in your experience that adding a second or even a third magnetometer would aid to make them usefull?
For a drone competition I was in charge of creating a small and light UGV that could bring a small 8-OZ water bottle. For this task I designed my own Controller namely an STM32L432 with BNO055 IMU, BME280 BARO and a CAM-M8Q GPS. I was able with this setup to do waypoint navigation using my own Firmware. The IMU did it’s own sensor fusion and it seemed to work pretty great after it’s calibration, considering it was practically above a DC motor. And I had no issue with the GPS whatsoever. Anyway that was my experience with custom autopilot hardware and software.
Have you looked into creating a custom carrier board for the Cube series - similar to the Kore Carrier Board and other variants? Definitely a bit heavier compared to a more compact board - but could minimize the amount of wiring you have to deal with. Some examples can be found here: CubePilot | Autopilot-on-Module | Blue Manufactured in USA | Blue Assembled in USA | Pixhawk Original Team
I was on the Virginia Tech team that competes in SUAS - and we have been using the Kore Carrier Board for the past couple years and really prefer it over the stock carrier board.
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This is one option we explored in our team but ultimately decided not to take this solution, mainly because we had an hexacopter.
As for what I want to do I think it would be a great solution. I liked the original cube carrier board since you could add an Intel Edison, which was killed by Intel soon after the release of the Pixhawk Cube Black, so I never could try that feature. I think a small carrier board with all missing components id possible, the only thing I don’t like about this solution is The Cube itself, I find it hard to use as a hobbyist. The inter-board connector is hard to solder by hand and fragile. And the price for the Cube is steep. I do have to admit that it is really well engineered the redundency and damping going on inside works really well. But I think for hobbyist it’s nice to have but not needed. When there is options for flight controllers for FPV drone at a quarter of the price (at least in canada, last time we ordered a cube we paid 400$ CAD for it and 250$ CAD for duty and shipping!!!). Even the Cube Purple is above 200$ CAD. I really have a hard time justifying the price tag at least to buy it for myself.
The Kore board works for hexacopters as well - but I understand that its shape/layout is more designed towards Quadcopters and X8s. I believe we competed in SUAS around the same time - so I remember when y’all switched over from the plane to a hexacopter.
Cube is pretty expensive - back before supply chain shortage it was only around $200 USD (still steep but a lot better than it is now). I understand how some could see it as “overkill” for a hobbyist project. It is, however, an easy way to access a large amount of the userbase and removes the need for an autopilot creation on your end. As a bonus - the carrier board design allows for a system that can continue to be updated with future Cube versions without any work on your end. We have swapped between the Cube Black and Orange on the Kore Carrier Board without any issues. Regardless - I will digress from that route as an option.
I think what you might be looking for is something similar to the ArduBee board - but I don’t know if it ever reached production.
mRobotics has a nice offering as well. Although it still requires a separate GPS and telemetry module.
This is like the system I would like to make it has everything needed for an autonomus flight, sadly it did not go into production, I will try to see what went wrong. What I had in mind is more simple and for hobbyist like myself and not toward big company.
I think the swarm sensors and other features might have scared people off. I barely can afford having a drone, let alone a swarm of them!
Do you know the OBAL system? It implements quite some of the functionality you want already (except additional UARTs), and proove already that it is actually working on a pi zero hard- and sofwarewise:
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I also think that there are many options for Ardupilot out on the market, which become cheaper and more capable, which will ask less compared to build a new FC from scratch.
Speedybee comes with ESCs at around 80USD, just as an example…