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Introduction To MewPro Bastet

MewPro Bastet is a small device that enables us to control/genlock GoPro Hero 4 cameras. Unlike our monolithic MewPro Iliad, it simply listens broadcast by the master and provides sync signals for all of cameras while recording.

MewPro Bastet is ready to purchase in our shop, however, its product description is still under construction (I’m now editing it…).


The following video shows the three Hero 4s are synced and controled by Wi-Fi RC. (Power on — change mode -(video)- start recording — stop -(photo)- take a photo — power off.)

To make the footage we used:

  • 3 GoPro Hero 4 Black (one master and two slaves)
  • 3 MewPro 2
  • 1 MewPro Bastet
  • (cables and plugs/receptacles)

The white PCB is Bastet, the blue PCBs are MewPro 2s.

In the photo above you’ll also find bulky RJ45 Ethernet receptacles or “Stackable Hub with Buffer”, however, these parts are not always necessary for syncing cameras in, for example, weight restricted environments such as shooting videos from the sky.

How It Works

In Fig. 1 the number of GoPro Hero 4 cameras is five for example. Of course, any number of cameras can be synced in this way.

MewPro Bastet is put between the master camera (GoPro #0 in Fig. 1) and the slaves (GoPro #1, #2, #3, #4 in Fig. 1). It wiretaps the command packets that the master sends to the slaves. It understands all commands and changes its internal states accordingly. And once master’s shutter button is depressed then it begins to generate sync signals (VSYNC/HSYNC).

Fig. 1

In the diagram above “Hub (optional)” can be either solder joints of wires or our Stackable Hub with Buffer or some kind of DIY octopus cable or a strip board with 6 lines in parallel or something. We only offer a solution with Stackable Hub with Buffer but you can do it yourself in place of this in order to reduce the space.

Comparison Table Between Iliad and Bastet

For your information the following is a brief comparison table between Iliad and Bastet.

Iliad Bastet
Size larger than Hero 4 equal to MewPro 2
MCU ATmega2560 ATmega328PB
LCD 16 x 2 none
Switches 3 0
Infra Red 1 0
Wi-Fi no master camera (*)
Software MewPro_Iliad MewPro_Iliad
MewPro 2 all slave all slave but one master (**)

Note *: All the cameras are controlled by the master regardless of whether the change is made by using Wi-Fi or master camera’s button press.

Note **: The MewPro 2 board attached to the master GoPro must have MewPro 4 firmware that is compiled with #define BASTET_MASTER compiler directive. While other boards should have the default MewPro 4 firmware.

How To Use MewPro Bastet

In the next blog post we’ll explain how to connect wires between Bastet and each MewPro boards.

Overexposure Bug Fixed

MewPro Iliad’s overexposure problem in many video modes is fixed.

The Iliad source code at our GitHub repo has already been updated to the latest 1.2.15. Compiling and installation guide is here. Since this bug only affected sync signal parameters there is no need to update the firmware on your MewPro 2 boards.

All the video modes that the camera, GoPro Hero 4 Black or Silver can shoot are supported.


Migrating from Hero 3+ Black to Hero 4

An old genlock rig using MewPro 2 with Hero 3+ Black and Genlock Dongle can be upgraded to Hero 4. The post explains migrating from Hero 3+ Black to Hero 4.

Example Rig Migration

Suppose you have a 6-camera rig that consists of

  • 6 GoPro Hero 3+ Black cameras
  • 5 MewPro 2 boards
  • 1 GoPro Dual Hero
  • 1 Genlock Dongle

and these are connected in single dongle configuration:

Single Dongle Configuration for 6 Hero 3+ Blacks

Single Dongle Configuration for 6 Hero 3+ Blacks

Then the GoPro Dual Hero bacpac and the Genlock dongle are not necessary from now on. And now you’ll need one more MewPro 2 board and one MewPro Iliad as well as 6 Hero 4 (Black or Silver) cameras.

Remove the Dual Hero bacpac and the Dongle from your rig. Replace Hero 3+ Black to Hero 4. Burn the “MewPro4” software ( to MewPro 2 boards.

The connection to each MewPro 2 board is the same as in single dongle configuration, however, TRIG signal is not used for Hero 4. And since Hero 4 can be fed power from side USB or herobus and works without internal battery the spare wire previously used for TRIG can be reused to connect 3.3V power from Iliad to each MewPro 2 board.

Upgraded Rig

After connecting Iliad to MewPro 2 boards the upgraded sytem is like this:


Hero 4 Power Supply

In order to avoid camera’s overheat Hero 4 had better be fed with external five volt source and use without internal battery. This post enumerates ways of power supply in MewPro + Iliad system.

Note: If your cameras are located in rather remote places then please avoid ground loop. For good explanation on ground loop and its potential danger, common mode current see this article “What should I do to avoid accidental damage to the device?” written by an engineer of a famous USB logic analyser Saleae.

Ways of Power Supply

The following shows each component (camera, MewPro, and Iliad) is fed with, wiring MewPro board, and remarks.

(Warning: If all cameras and Iliad are powered by one big battery or one wall charger then please notice that there are ground loops. As ground loop itself is not harm, however, care should be taken to avoid accidental large common mode current. It is suggested that you’d better remove GND connection at each MewPro’s RJ45 connector in this case for getting around this.)

Power ON = auto” means a long press of the mode button at Iliad makes camera’s power on. Similarly, “Power OFF = auto” means off.

Power ON = manual” is a special case where we currently can’t power on using Iliad. We don’t know the reason why we can’t and it’s a shame, however, we gave up further experiment on the power method after several days of fruitless effort followed by nearly ruining/burning a Hero 4 Black by carelessly connecting a wrong power line. In this case we can power on cameras as in the following steps:

  1. Connect all cables and wires but power lines. Attach MewPro’s to cameras.
  2. Connect USB wallcharger or battery pack to Iliad (or DC 7-12V to Iliad’s barrel jack).
  3. Apply 5V to USB VBUS pin of MewPro 2 board.
  4. Power on each camera by manually long press camera’s mode button.
  5. Long press Iliad’s mode button

Power on this way also syncs all the settings stored in Iliad.

UPDATE 2 Dec 2016: A workaround is found for the last annoying case of “Power ON = manual“. By using a paper clip (see photo below) or scotch tape or something we can fix camera’s mode button to ON state.
Then the camera’s power can be controlled by applying 5V to USB VBUS pin. And once the camera powered on then Iliad can control everything of it. The trick is that button “press” is actually recognized by the camera when the button is “released” while “long press” is recognized by its pushed state.

Our recommended power supply method is the connection depicted in Table 2. If you order plug-n-play tailor made sets in our shop then we will use this wiring.


Table 1
MewPro 2 Iliad
Table 2
MewPro 2 Iliad
Table 3
MewPro 2 Iliad

*: USB VBUS as well as GND is connected to external 5V power supply. It must be “good” source as each camera requires 1A or less while recording.