Gorgeous sunset FPV with Xiaomi Yi

We were flying our FPV gliders the whole day but at sunset it was time for at least one flight with our wings:

One scene was captured with the SJ5000+ (you will notice it, because that’s the only scene where you can see my little Wipeout wing in front and you might notice some ghosting in the image because of different framerates), every thing else is footage from the Xiaomi Yi :-)

Xiaomi Yi – Tips and Infos

Xiaomi Yi


 Battery-Life


My first two endurance tests showed that my Xiaomi Yi was able to capture ~100 minutes in 1080p @25fps.

I configured the LEDs so that only the recording indicator LEDs are active (LED ring of the power button and WiFi LED are off) and WiFi was turned off.

The battery of my Yi has only past ~two charging cycles, so the battery life may slightly increase, after some more charging cycles.

If you capture in 1080p @50/60 fps the battery life will definitely decrease. I think ~60 minutes are realistic in that mode.

Battery Drain Fix!: If you notice some awful battery drain while the cam is off, your Yi might have some kind of connection between the backup battery and a metal frame inside the cam. Here is a short description how to fix it.


Bitrate / Custom Firmware


In the DashCamTalk forum there are some useful threads about the Xiaomi Yi.

For example this one, where you can find modded firmwares with higher bitrates and also a link + tutorial for creating your own custom firmware: https://forum.dashcamtalk.com/threads/xiaomi-yi-sports-camera-custom-firmware-base-1-0-7-bitrate-increased-to-30mbps-all-modes.10410/

With the stock firmware you will get 12mbps at 1080p @25fps with quality “high” (there are different data rates for the different resolution/frame rates and quality settings). My GoPro 2 will record in 14.6mbps at 1080p 25fps which seems to be good enough, although it’s not much higher than the bitrate on the Yi cam.

The 12mbps that the Yi cam uses in that mode will result in some blurry areas if there is much action going on in the scene (many details that are moving, like the footage that you will see when flying very low and fast).

The video files will be split in ~1.95 GB parts and those will be ~22 minutes long (in 1080p 25fps “high” quality).
Here is a link to a modded firmware which will allow you to get much higher bitrates. In my preferred setting (1080p 25fps) this firmware allows me to choose between 8 / 20 / 25 mbps (low / normal / high quality).

With 20mbps the files will still be split in 1.95 GB parts and they will contain footage of ~14 minutes.


Correcting the focus to infinity


Here is the link which describes how you can open your Xiaomi Yi and correct the focus, if necessary (many people report sharpness problems which are caused by a wrong focused lens).

You basically just have to remove the front of the cam (use a knife or something similar to open it) and then remove the hot glue spots around the lens. After that you can screw the lens in and out to refocus.


Problems / Bugs


The only problem that I was not able to get rid off is the file transfer via USB. My Xiaomi Yi crashes when I try to copy the files from the microSD card via USB. I tried many different cables and microSD cards, but for now the only way to get my video files is to remove the microSD card and put it in my cardreader.


Image Quality Xiaomi Yi vs. GoPro 2


You might have seen the footage that I captured with the Yi / GoPro 2 / Mobius. This time I just lined up the GoPro 2 and Xiaomi Yi footage side by side, so it’s easier to see how they compare.

In my opinion the Yi does a great job (good white balance, details and sharpness), especially for the attractive price.

HOWTO – APM power distribution

The Ardupilot platform is a nice open source autopilot and stabilization system. It can be used in a variaty of airframes, so I decided to install one in my new No.1 flying wing. Why did I choose the APM?

  • It is a reliable and highly customizable system
  • Offers a completly customizable OSD (minimOSD)
  • It is affordable (80$ for a miniAPM with OSD, current sensor and NEO-6M GPS [at least for china clones])

For now, I did not pay attention to the autopilot functions of the APM, I just use the “ACRO” stabilization. But still, the large amount of functions that can be configured by the user come at a price: the APM has a very steep learning curve, even if you just want to use basic functionality. It took me quite some time to get everything running smoothly. So this will be the first article in a small series where I will try to summarize how I set up the APM.

The first thing that you need to figure out is how to power everything without getting a nasty ground loop or having the OSD flicker like hell when you fire up your ESC ;) So this is what I ended up with:

APM_power

Actually it is pretty straight forward. The diode between the boost-buck and the LC-filter is important to prevent them from forming a resonator. I adjusted the Boost-Buck’s voltage to compensate for the voltage drop over the diode and the LC-filter, that way I get constant 12V to power my FPV gear.
The only thing that took some experimenting was how to power the minimOSD. On my board, ground of the 12V and the 5V side was already connected. So make sure not to connect ground on both sides, otherwise you’ll end up with a groundloop. The first thing I did was modding the OSD following this guide from flitetest (it’s easier to just connect one power source instead of two). My initial plan was to power the OSD from the 5V side only, so on the 12V side I would just connect the two video lines. But that didn’t work out so well, every time i started the motor the OSD began to flicker and/or was barely visible. It turns out that connecting power on the 12V side, in addition to having the 5V mod in place so that the 5V side gets powered by the stepdown of the 12V side, works just fine.

In the next post I will cover how to connect the miniAPM with the RC gear (RX and servos) in more detail.