Archive / March, 2015

How To Use MewPro Genlock Dongle

The post is to show you how Genlock Dongle(s) and MewPros work and to explain how to wire them.

Two GoPro Hero 3+ Blacks can record videos/photos in genlock by using Dual Hero System. But more than two it was impossible by now. MewPro Genlock Dongle is a hardware emulator of GoPro camera who communicates with Dual Hero System and steals the required signals, VSYNC and HSYNC, that are generated by Dual Hero System.

How Dongle Works

Here is a demo video of syncing four GoPros. They sync when power on/off, changing modes/settings and shooting.

To make the above video we use the following items:

qty
GoPro Hero 3+ Black n
MewPro n-1
Genlock Dongle 1
USB battery pack 1
Cables and wires

(Note: n is the number of cameras. In our case n=4.)

These items are connected as follows:

Single dongle configuration

Single dongle configuration

  • TRIG: Generated by Dual Hero for start/stop recording
  • VSYNC: Generated by Dual Hero for syncing frames
  • HSYNC: Generated by Dual Hero for syncing scan lines
  • GND: Signal ground
  • UART lines (TXO/RXI) are used by MewPros and Dongle(s) for transferring settings/modes from GoPro #0 to other GoPros (*)
  • RESET line is optional but useful when an error occured. Depressing a reset button on any Arduino Pro Minis will reset all the boards, which has the same effect as detaching/attaching the boards manually

A USB battery pack or wall charger is needed to power the dongle through USB connector of Dual Hero.

* Note: GoPro #0 controls everything: Modes, settings, and start/stop recordings. Commands from GoPro #0 are distributed to other GoPros through UART lines. This transfer is one way without feedback; if another GoPro is busy to do something a message from #0 may be ignored. However, since UART lines are nothing to do with TRIG/VSYNC/HSYNC this unreliability only happens before or after recordings and doesn’t harm video/photo quality.

Alternate Configuration

The above single dongle configuration is normally sufficient and recommended for any new installations of many GoPros in a rig as it needs the minimum number of equipments. But in some cases or already existing rigs following another configuration may be preferred:

qty
GoPro Hero 3+ Black n
MewPro n
Genlock Dongle 2
USB battery pack 1
Cables and wires

(Note: n is the number of cameras. In our case n=4.)

The wiring is as follows:

Double dongle configuration

Double dongle configuration

Advantages of double over single include symmetric wiring (except the UART line between MewPro #0 and Dongle #1) and the less space required on the back of GoPro #0.

Here is the similar demo of the double dongle configuration: Power on, changing modes, shooting, power off.

How To Wire Boards

Both in single and double dongle configurations connections between Dongle #1 and MewPro #i (i=0,1,2,…,n) is summarized as follows:
wiring

It is clear that the only difference on wiring in two configurations is whether MewPro #0 exists or not.

All of these wires need to be soldered by yourself to the boards: Please refer the following pictures.

Wires to Dongle #1

Wires to Dongle #1

Wires to MewPro

Wires to MewPro 1

Wires to MewPro 2

Wires to MewPro 2

Wires of MewPro Cable

Wires of MewPro Cable

(Update:29 Jun 2015, 7 Sep 2015. Added figures for MewPro 2 and MewPro cable boards.)

Remark: We only confirmed the configurations work with four GoPro Hero 3+ Blacks and the wire length less than 30cm. If your number of cameras or length of a wire exceed these limits there is no warranty but there is always hope: Please try shortest lengths of wires as possible!

References To Other Resources

Sample Videos by Four H3+B and Genlock Dongle

PCB of Genlock Dongle has arrived for us. Here are example shots by using it.

Tonight I went nearby streetcar station and test the dongle. The equipment is as in the following photo and four GoPro Hero 3+ Blacks.

Genlock Dongle connected to 4 MewPros

Genlock Dongle connected to 4 MewPros

(FYI: There are three dongles in the photo above; Connected, box opened, the reverse side.)

I set the cameras on the platform.
IMG_6156

And shoot.



Note: These videos are completely untouched. No editing at all. This is why three videos are upside down. 🙂

Next post of this blog will be the announcement the item being ready for purchase. So stay tuned.

Genlocking HSYNC/VSYNC details

Here are screenshots of logic analyzer showing HSYNC and VSYNC signals while recording in 1080-30.

These signals are generated by the micro processor in the right bacpac of Dual Hero System. You can easily see that the periods are equal to those of lines and frames, respectively.

HSYNC @1080-30

HSYNC @1080-30


VSYNC @1080-30

VSYNC @1080-30


Note: The PCB for MewPro Genlock Dongle is on the way to our lab in Tokyo. We expect they will arrive in a few days.