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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.


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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:


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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.

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Hero 4 Firmwares and I2C/Herobus Commands

Newer firmwares for Hero 4 cameras have a fatal bug in bulk transfer of the settings. This post get to the core of its reason by arranging events in chronological order.

Bulk Transfer Bug

In order to sync camera’s settings Hero 4 Black/Silver has two kinds of I2C/Herobus commands:

  • Bulk transfer
  • Individual transfer

The bulk transfer sets each of the video/photo/multi-shot settings at once. This is usually useful at boot process of camera, whereas an I2C/Herobus command for the individual transfer is issued from user interaction with LCD menu.

Newer firmwares for Hero 4 cameras can’t do the former. So if you like to use some new function introduced in the buggy firmwares then you must prepare the camera mode in advance and it’s better not to change it in the field.

Debug messages for firmware 04.00.00. Bulk transfer of video/photo settings returns an error code (0xfc).
Debug messages for firmware 04.00.00: Bulk transfer of video/photo settings returns an error code (0xfc).

History of Hero 4 Firmwares

It is said that “Good intent and good deed contribute to good karma and future happiness, and vice versa”. So let’s investigate GoPro’s actions in time sequence.

05 Oct 2014: version 01.00.04 (Black) / 01.00.00 (Silver)
These are the firmwares for Black and Silver cameras at product release.
14 Oct 2014: version 01.02.00 (Black, Silver)
No I2C/Herobus commands are supported, yet.
04 Feb 2015: version 02.00.00 (Black, Silver)
There is a support for a kind of I2C/Herobus commands, which is a bit different from the current one or discontinued Dual Hero’s.
28 May 2015:
Google and GoPro announce a VR project, which finally evolved into GoPro Odyssey after tired waiting for more than a year, at Google I/O 2015.
30 Jul 2015: version 03.00.00 (Black, Silver)
Current I2C/Herobus commands are fully implemented without a flaw.
01 Jun 2016:
GoPro Odyssey is released. Instead utilizing Black’s default firmware user must install Odyssey exclusive, privileged firmware 16.01.10 to their Blacks. It can shoot in 2.7K 4:3 30/25 (NTSC/PAL) only.
17 Aug 2016:
GoPro Omni is released. User must install Omni exclusive, privileged firmware 26.01.10 to their Blacks. It can shoot in not only 2.7K 4:3 30/25 but also 1440 4:3 60/50 (NTSC/PAL).
18 Aug 2016: version 04.00.00 (Black, Silver)
Bulk transfer bug is put.
21 Oct 2016: version 05.00.00 (Black, Silver)
The update is exclusively for supporting Karma. Still the bug is there…
23 Oct 2016:
GoPro Karma is released. It works with version 05.00.00 firmware.


We wish we could test the firmware 05.00.00 with Black and Karma, however, it became impossible now as bad karma fell from the sky.

Note: Hero 4 Silver with firmware version 03.00.00 or later is now supported by MewPro Iliad software published at our GitHub repo (please edit/define the compiler directive HERO_4_SILVER in Iliad.h and compile/upload it). No change is necessary for MewPro4 software to use with Silver.