A DIY stand-alone unit for watching geofence breach is made by using Teensy 3. The general purpose device, which has a similar functionality of geofence or sending notification by location on smartphones, is also usable to automatically start/stop recordings of GoPro camera with aid of MewPro.
Details
Although each MewPro has a microcontroller (AVR) on its board, we decided to separately use Teensy 3 (Cortex-M4) that can do with double-precision floating-point (64 bits) numbers. Implementing geofence as stand-alone enables the unit to control not only GoPro cameras but also other equipments (such as LEDs and buzzers) with regard to preconfigured geofence, which can be a union of convex polygons.
Connect to LED to Test Geofence Function
To test the unit we connect an LED to its alarm pin: SHUTTER signal (red wire) at the audio mini plug in the photo becomes LOW/hi-Z if it enters/exits the geofenced area. We use digistump’s ATtiny85 Digispark board to watch the pin and to turn on/off the LED, however, you can use any device such as GoPro+MewPro or something as Digispark.
The following is a teardown of the DIY unit.
Resources
The module is an open software/hardware. The schematics and the source code with a simple README document are downloadable from:
By syncing GoPros and utilizing GPS it is demonstrated how to accurately measure time of an observed event.
For example, taking astronomical videos or photos it is usually important to record the time when those captures were made. Both professional and amateur astronomers interested in especially eclipses or occultations, such as the Moon passes in front of a star, have ever invented many kind of timekeeping devices for this purpose. Needless to say the more exact, the more preferable.
The post proposes a new convenient method to keep time whose precision is within several milliseconds or the duration of one video frame.
The idea is based on the following facts:
Any number of GoPro cameras can be genlocked or in sync by every frame and scan line to a timing generator.
Some GPS receiver can output a pulse-per-second (1PPS) signal that have an accuracy of nanoseconds.
Unfortunately we cannot synchronize these two signals, the ones from the genlocking source and the 1PPS. However, we can easily record both of them together by visualizing the latter using LED and pointing one of all cameras in sync with the former to the LED.
In the rest of the post we will perform an experiment to confirm that the precision is kept within one frame while capturing videos.
Measurement
To assure perfectness of the sync we use the following equipments:
Microcontroller boards, OLED (Organic Light-Emitting Diodes) character displays and LEDs
These are required for displaying GPS time in a form of hh:mm:ss (hh=hour, mm=minute, ss=second) and every zero second.
MacBook Air
To show the NTP Internet time for intuitive reference.
Block diagram of measurement equipments
We use three cameras in sync: Two cameras are pointed to LEDs and OLED character displays (another camera is to control the two). Two GPS receivers are of different brands: Each 1PPS signal is aligned to UTC and visualized as hh:mm:ss on the OLED display, and lights the LED when asserted.
Doing this requires some microcontrollers between the GPS receivers and the I2C OLED character displays we use Teensy 3.1 and Arduino Due boards. And in order to make sure that our programs running on these doesn’t have any bugs we also prepare a MacBook Air to show the Internet time that is obtained from an NTP server.
Results and Discussion
The following are clipped from the videos (WVGA, 240fps) shot by the two of genlocked cameras:
(One frame before 2016-05-27T02:15:46.000Z. Up: View from the right. Bottom: View from the left.)
The blue LEDs haven’t lit yet (cf. the next two images). The MacBook Air behind is slowly changing its time display from 02:15:45 to 02:15:46, however, it turns out to be not so accurate as 1PPS time. The right OLED display shows nothing: This means the OLED, which is always blinking in order to reduce power consumption, is in an off period. At the same time the left is on the way to refresh 02:15:45.
Each of above frames is followed by the next, respectively:
(Exactly it is 2016-05-27T02:15:46.000Z. Up: View from the right. Bottom: View from the left.)
Both of the blue LEDs light. The right OLED display shows the time as 02:15:45. According to GPS’ protocol (aka NMEA) specifications, a rising edge of 1PPS signal occurs on an exact zero second, which is followed by a GPZDA statement aligned to UTC. In the current system the blue LED lights when 1PPS is asserted, and OLED is rewritten when a GPZDA is received by the microcontroller. So it is no wonder that our OLED is not updated yet this time. The left OLED is on its way to erase 02:15:45.
These four images proved the exactness of sync among not only the cameras but also the GPS receivers. And we confirmed the system could be utilized for exact time measurements of events.
Reference
The above stills are extracted from the following unmodified original movies (MP4 files):
A detail of our open-hardware rig, Mani Wheel, which you can make or buy, is addressed in this article.
In the previous post we published two 360-degree videos of Japanese Cat/Rabbit Islands. These clips are made by using the following hardware and software:
Connected to the serial lines (RxD/TxD) of Dongle #0. And the whole system is controlled through BLE from the terminal application installed on iPhone or PC. (Note: In GenlockDongle source code, the serial baud rate must be modified from the default of 57600 to 9600 for Dongle #0.)
Software
Kolor Autopano Video Pro
Exact sync is detected by the software automatically.
YouTube 360 Video Metadata Tool
This is necessary for uploading 360-degree video to YouTube.
The hardware items are connected as in the following figure:
to supply 5V power to Dual Hero and Dongles through the USB connector. However, this can be done by any USB battery pack.
The following is top view of our Mani Wheel Rig:
Two Dongles (black small/large casings) and a Lipo battery can be seen. Next photo shows the inside of Dongles’ casings:
Opening and removing the orange top lid enables us to look inside of the hexagonal cavity consisting of six cameras. There sits a dedicated PCB disk to simplify soldering:
Note: We can sell 3D printed lids (top and bottom) and dedicated PCB disks starting from 200.00USD. Please ask us for detailed pricing of the items and/or extra soldering charge if you don’t want to do it by yourself.
UPDATE 22 May 2017: We received a STL file from Julien Brault-Chénier at LEOFILMS.CA. Thank you, Julien! The file can be 3D-printed and fit to use in place of our top lid so that the Mani Wheel rig can hold one more camera for shooting the zenith. (The STL file is also downloadable from our GitHub repo.)
We have uploaded two 360-degree videos shot using six GoPro Hero 3+ Blacks and MewPros.
Note 1. Please watch these clips in HD settings and use the navigation wheel at the top left corner. Currently 360-degree viewing is possible in Chrome, Edge or Firefox. Note 2. If you are viewing them on iPhone please launch the YouTube app and flick to turn around. Current Google Cardboard app for iOS doesn’t support any 360-degree video view of YouTube yet, meantime with VR glasses as Google Cardboard please try in360Tube app.
iOS: Open this video in YouTube app