Open.HD for Dummies (for Marvin Lange)
When a project reaches a certain stage, the number of options can be very overwhelming. This section of the documentation is intended to help guide newcomers towards their first functional Open.HD implementation.
If you have a pre-existing hardware requirement that is not met in this guide, it is still a good idea to follow the guide and make sure you have this, the simplest setup, working before venturing into more complex builds. Every setup, no matter how complex uses the elements in this guide as it's base.
Assuming you are starting with nothing, we recommend you get the following hardware:
A Raspberry Pi4B for the Ground SBC
A Raspberry Pi3A+ or Raspberry Pi Zero for the Air SBC
A Raspberry Pi Zero 2 . We no longer recommend a Pi Zero 1, it most likely will be depreciated. (Raspberry Pi Zero needs a different CSI cable)
Two WiFi cards that support the band you want to use. (See WiFi Adapters)
An HDMI cable for connecting the Ground SBC to a screen
An HDMI capable screen (you can use your TV for testing!)
Two High class SD Cards of 8Gb or more
An SD card Adapter for your computer to flash the cards.
A mobile device capable of running QOpen.HD and connecting to the Ground SBC (optional)
Two BEC's for powering the Air and Ground SBC's. (See Guidelines)
Various lengths of connection wires.
A soldering iron and required disposables.
Now that you have your prerequisite hard- and software, we can get down to business.
This is where the BEC's come in. Much like the Air SBC, the Ground SBC will likely be powered by a LiPo battery. The Raspberry Pi and the WiFi cards all use 5V, which is what most BEC's produce. So hook up one of your SBC's to a LiPo battery and use a multimeter to double-check the output is +5V.
The Raspberry Pi and most WiFi adapters actually like the voltage to be slightly higher than +5V, along the lines of 5.2V ~ 5.4V. If you have a variable output, best set it to +5.3V. Do not go higher than +5.4V or you will damage your Raspberry Pi and/or WiFi cards!
When you have verified the output of the BEC, we can connect it to the Raspberry Pi, to do this, we have two options. Soldering or using the GPIO Pin Header, for the Ground SBC it's OK to use the GPIO Pin Header, for the Air unit we recommend soldering. Connect the output from the BEC to the PI on pins 2 and 6 (or 4 and 6) according to this diagram:
This can be done easily by just plugging in the Servo header that comes with most BECs into the Raspberry Pi Pin Header. Make sure the RED wire is connecting to Pin 2 or 4 and the BLACK wire is connecting to PIN 6. Now when you connect power to the BEC, the Raspberry Pi will power up!
For all following steps, make sure to disconnect the power before attaching anything to the Raspberry Pi unless explicitly stated.
Now that we have power going to the Raspberry Pi it's time to complicate things. Attaching WiFi cards should be as easy as plugging them into the Pi's USB ports, unfortunately it isn't. Due to the way the Raspberry Pi is designed the USB ports do not receive enough power to drive the WiFi cards, especially when connecting more than one WiFi card as is often the case on a ground station.
So we need to make sure we provide enough power to the WiFi card while still attaching it to the Raspberry Pi's USB port. There are several ways to do this, including using a USB HUB and powering that from the BEC. Take a look at Wiring for inspiration. For this step-by-step we will create a modified USB cable.
Using the diagram above create a USB cable with the D+ and D- soldered to the Raspberry Pi and the +5V and GND soldered to the BEC.
While it may seem tempting to solder the +5V and GND to the solder points on the Raspberry Pi, doing so is not OK! We will be feeding +5V into the circuit of the Pi where this is not intended, probably destroying the USB controller. Make sure the +5V wire of the USB cable is no longer connected on the Pi side. GND is OK connected or unconnected to the Pi.
For this step-by-step we will just connect a display to the HDMI port, any TV or monitor with HDMI in will be useable. Bear in mind that bringing your 85" flatscreen TV to the field might be impractical. So for a more portable setup use a small HDMI capable monitor or use the 7" Raspberry Pi Touch Screen and create the ultimate GCS. (See examples here)
Now that we have all the hardware connected to the Ground SBC it's time to put Open.HD on an SD card and boot it up! In order to put Open.HD on an SD card please follow these steps:
Go to the release of Open.HD and download the latest release.
Extract the archive to a place on your computer where you can find it again.
You should now have a .img file.
Download and install Balena Etcher for your OS.
Put the SD card in the SD card reader (if you don't have one in your PC or laptop, get a USB to SD card adapter, they can be found for cheap, but investing in a slightly more expensive high speed adapter will greatly reduce the time spent staring at the progress bar of Balena Etcher)
If your OS prompts you to format the card, ignore that.
Start Balena Etcher.
Select the .img file we downloaded and extracted earlier for the image file.
Select the SD card as the target (Balena Etcher should only show the SD cards, but be careful, double-check that the indicated size matches the SD card).
Hit write and wat for the process to complete, depending on your SD card adapter this can take minutes to an hour.
When Balena Etcher finishes it will automatically dismount the SD card making it safe to unplug it from your computer.
Put the SD card in your Ground SBC.
Pro tip: Start the second SD card for the Air unit before continuing to the next step, Air and Ground use the same image. That way it will be done when we arrive at the Air unit steps.
Now that we have everything connected to the Ground SBC, it's time to plug in the power.
When bench-testing you can use a bench power supply instead of a LiPo to prevent draining the LiPo, but make sure it can supply the required Amps (minimum 3A). When using a LiPo, connect a LiPo warning device to prevent over-discharging!
If everything went well, you should see the SBC boot up and eventually show the QOpen.HD screen on the connected HDMI monitor. If for some reason it does not, please go back and make sure you have followed all the steps exactly as described.
If you happen to be lucky and you are running on a touchscreen you can go ahead and press the Open.HD logo in the top left corner. You will see the menu system that allows you to configure all the settings. If you don't have a touchscreen, don't worry, you can attach a mouse and/or keyboard to the Ground SBC and use those as well!
Optionally you can connect a mobile device (Phone or Tablet) with the QOpen.HD App installed to the ground station. By default the Open.HD image will create a 'hotspot' WiFi network to which you can connect with the device. The default network name will be Open.HD and the password will be wifiopenhd.
When connected to the hotspot start the QOpen.HD app on your device. If all went well you should see the same interface as on the HDMI monitor. Since we don't have an Air device yet it will show a black screen with the HUD, but you should see the Temperature and CPU load of the Ground SBC change as on the HDMI monitor.
TODO: Picture
Power for the Air SBC is much like powering the Ground SBC. So use the steps described there to make sure you hook up an BEC with enough Amps to the Air SBC. Please try to solder as much of the connections that you can, soldering will prevent many troubleshooting steps later on.
Since it is quite common to use a Raspberry Pi Zero for the Air SBC here are some schematics for hooking up power AND connecting the WiFi card to that SBC.
As you can see both the USB Cable and the Pi are fed power from the BEC.
Please make sure the USB connector on the WiFi Adapter side is also secured, some people solder the USB connectors together, some people use glue, whatever you do, make sure it can not wiggle or disconnect. Even an tiny wiggle might temporarily disconnect the WiFi card resulting in a complete loss of signal from the Air SBC.
This step is mostly covered in the diagram shown above. Let's reiterate that, however tempting it might be, do NOT use the USB connectors on the Pi to connect the WiFi Adapter with a standard cable, you might get lucky, but soldering is the only way to prevent costly lessons.
We will now attach the CSI camera to the Air SBC, this is a very simple procedure, but you need to make sure to connect the cable 'the right way around' on both ends. First let's take a look at the ports on the Raspberry Pi's.
The pictures above should make it clear how to inspect the camera, but for good measure, here is the connector on the camera side:
So now that we know where the pins are on the boards, let's inspect the CSI cable itself.
So now it's a matter of inserting the cable into the ports with the pins of the cable facing the pins of the connector, pull up the locking tab and insert the cable:
Now using equal pressure on both sides gently push the locking tab all the way down while making sure the cable does not slide out:
Make sure the cable is properly seated before continuing.
Now do the same on the Camera connector. The procedure on the Raspberry Pi Zero is the same, the CSI connector is a bit smaller and in a different place, but it works the same. Be aware that you need a different CSI cable for the Raspberry Pi Zero due to the smaller connector.
The CSI camera is the simplest option to use and usually yields the best performance. The CSI cables however, are quite susceptible to noise and interference. If you see horizontal lines or odd discoloration in the image, shield the CSI cable by wrapping it in tin foil or other conductive material.
Now if you've been following the steps to the letter you will already have an SD card from step 5. If not, please use the instructions from step 5 to create a second SD card for the Air SBC.
Good, now it's a simple matter of inserting the SD card into the Air Pi and your air unit is good to go!
So now comes the moment of truth, apply power to the Ground SBC and subsequently apply power to the Air SBC. Allow both to boot completely, most CSI cameras have a small LED that lights up when the camera is activated, this is a good indication the boot went well and the system has started.
The Raspberry Pi Zero might take a long while to boot up, please allow a couple of minutes before despairing!
When all went well, and for the sake of this step-by-step we will assume so, you will be greeted by a nice crisp HD video streaming from your Air SBC to your Ground SBC, go ahead and wave at yourself to get a feel for the latency. Please notice that when using the HDMI out to a TV, the TV itself might introduce quite some latency.
Go ahead, celebrate your success, and please let us know if it worked for you! If for some reason the system does not work for you and you are sure you have followed all the steps, please contact us on Telegram or on the Forums to get help.
Logically most user will want to connect their Flight Controller to the system to actually see the OSD do it's thing. To do this, follow the steps outlined in Wiring -> Flight Controller and then make sure to use the correct settings in Telemetry and OSD. After that, you can look into RC Control over Open.HD as well as the subjects in the Advanced Setup.
