Introduction

SeeStar is an open-source oceanographic imaging system developed at the Monterey Bay Aquarium Research Institute (MBARI). It is a modular, low-cost, and light weight subsea imaging system for mid- to long term monitoring of marine ecosystems. The system can be deployed in a variety of scenarios taking either still images or video and can be operated either autonomously or tethered on a range of platforms including ROVs, AUVs, landers, piers, or moorings. The design priorities included using off-the-shelf and easily available components as much as possible, and to provide all designs, schematics, and fabrication documents online as open source, so that others can easily build and adapt the imaging system for their own needs.

System Level Description

SeeStar is composed of separate camera, LED light, and battery modules, each rated to 300 meters of depth. They share a common 8-pin bus using the micro series of underwater connectors and cables from SubConn. The camera module contains a microcontroller based board which acts as the brains of the system; it is responsible for triggering the camera and LED lights.

System Capabilities

The SeeStar Imaging System is based on the GoPro Hero 3 and 3+ cameras. The specific resolutions and modes are dependent on the model installed in your SeeStar camera module.

Image Taking Modes

Hero 3 White
5MP Wide

Hero 3+ Silver
5MP Medium
7MP Wide
10MP Wide

Hero 3+ Black
5MP Medium
7MP Medium
7MP Wide
12MP Wide

Video Modes

Hero 3 White
1080p (16:9) 30, 25 fps, medium FOV
960p (4:3) 30, 25 fps, ultra wide FOV
720p (16:9) 60, 50, 30, 25 fps, ultra wide FOV
WVGA (16:9) 60, 50 fps, ultra wide FOV

Hero 3+ Silver
1080p (16:9) 60, 50, 30, 25 fps, narrow, medium, ultra wide FOV
960p (4:3) 60, 50, 30, 25 fps, ultra wide FOV
720p (16:9) 120, 100, 60, 50, 30, 25 fps, ultra wide FOV
WVGA (16:9) 120, 100, 60, 50 fps, ultra wide FOV

Hero 3+ Black
4K (16:9) 15, 12.5 fps, ultra wide FOV, Protune
4K (17:9) 12 fps, ultra wide FOV, Protune
2.7K (16:9) 30, 25 fps, medium, ultra wide FOV, Protune
2.7K (17:9) 24 fps, medium, ultra wide FOV, Protune
1440p (4:3) 48, 30, 25, 24 fps, ultra wide FOV, Protune
1080p (16:9) 60, 50, 48, 30, 25, 24 fps, narrow, medium, ultra wide FOV, Protune
1080p SuperView (16:9) 48, 30, 25, 24 fps, ultra wide FOV, Protune
960p (4:3) 100, 60, 50, 30, 48 fps, ultra wide FOV, Protune
720p (16:9) 120, 100, 60, 50 fps, narrow, medium, ultra wide FOV, Protune
720p SuperView (16:9) 100, 60, 50, 30, 48 fps, ultra wide FOV, Protune
WVGA (16:9) 240 fps, ultra wide FOV

Note to user:
Consult the appropriate GoPro user's guide for more information on alternate operating modes.

Battery Capacity

The standard rechargeable Nickel Metal Hydride (NiMH) battery module has a total capacity of 4500 mAH.

The primary Lithium Sulfur Dioxide (LiSO2) battery module has a total capacity of 16500 mAH.

Number of Images/Video

The total number of images per deployment is dependent upon a number of variables:

1. Battery Capacity
2. Size of SD Card
3. Imaging or Video Mode Selected

The energy per image (including the LED light) is 1.4 mAH/shot. So, based solely on battery capacity, the NiMH battery module has enough energy for (4500/1.4) 3200 images.

The approximate size of images at various resolutions:

5MP medium: 1.6MB
7MP medium: 2.0MB
7MP wide: 2.0MB
12MP wide: 3.3MB

If 3200 images were taken at 12MP wide, that would require 10.6GB of storage.

Preparing SeeStar for Deployment

Setting up SeeStar for Images & Videos

1. Set up the GoPro for appropriate mode
2. Install a script onto the SD card
3. Program the Controller board

Sealing the Housings

Charging the NiMH Battery Module

The preferred method of recharging the NiMH battery module is to provide a current of 420mA for 16 hours. The charging voltage should be a couple of volts above the maximum battery voltage. A fully charged NiMH battery module will have 21Vdc so the charging voltage should be around 24 Vdc.

It is possible to to charge the module faster by providing a higher current. However, this will shorten the battery's lifespan due to heating from the excessive current.

Programming the Controller Board

GoPro Hero 3/3+ Camera Setup

Prior to deployment, the camera itself needs to be setup properly. How the camera is configured depends on the how SeeStar will be used and the complexity of the installed script. The Hero cameras have an extensive menu system which is accessible using both the power and shutter buttons (figure xx).

Default Power Up Mode

The Hero cameras have a user programmable power up default mode of operation, such as picture taking or recording video. Most scripts are written with the assumption that the camera will power up in a specific mode. For instance, if the user intends to take one image at a time, they would set the Hero to power up in image mode and then install a script for image taking (see the GoPro Hero 3/3+ Scripts section for details).

Power Saving Steps

In order to save battery energy, the Hero camera can have certain functions disabled during deployments.

1. Disable WiFi
2. Disable all front panel LEDs
3. Disable all audio alarms
   

GoPro Hero 3/3+ Scripts

The Hero 3/3+ cameras can be controlled remotely via the use of command scripts stored on the SD card. When the Hero 3/3+ is powered up, the script is automatically executed. The scripts can be written to emulate most Hero 3/3+ functions usually available to the user via the power and mode buttons. While there is an extensive list of commands available for use with the scripts, this document will cover only the basic commands for taking images and videos.

Note to user:
Some of the script commands are not compatible for both the Hero 3 and Hero 3+. Verify your camera model before transferring the script onto the SD card.

Commands

t app appmode [photo | video]

Description:

Places the Hero 3/3+ in either photo or video mode.

Usage:
t app appmode photo (put the Hero 3/3+ in image taking mode)

t app button [power | shutter] [P | R]

Description:

Software equivalent of pressing either power or shutter button.

power: Power button

shutter: Shutter button

P: Press

R: Release

Usage:
t app button shutter P (press the shutter button)
t app button shutter R (release the shutter button)
t app button shutter PR (press and then immediately release the shutter button)

t app sleep [x]

Description:

Pause between actions.

Argument: x, time in seconds

Usage:
t app sleep 5 (wait 5 seconds)

poweroff yes reboot yes

Description:

Powers down the Hero 3+. (Only works on the Hero 3+, not Hero 3)

Usage:
poweroff yes
reboot yes

Note to user:
To power down a Hero 3, do so using the power button commands:

t app button power P
sleep 3
t app button power R

Example Scripts

HERO 3

Take one image, wait 5 seconds and power down
sleep 5
t app button shutter PR
sleep 5
t app button power P
sleep 3
t app button power R

Note to user:
The Hero 3 must be set to come up in photo mode for the above script to work.

Take 60 seconds of video, wait 10 seconds and power down
sleep 5
t app button shutter PR
sleep 60
t app button shutter PR
sleep 10
t app button power P
sleep 3
t app button power R

Note to user:
The Hero 3 must be set to come up in video mode for the above script to work.

HERO 3+

Take one image, wait 5 seconds and power down
sleep 5
t app button shutter PR
sleep 5
poweroff yes
reboot yes

Note to user:
The Hero 3 must be set to come up in photo mode for the above script to work.

Take 60 seconds of video, wait 10 seconds and power down
sleep 5
t app button shutter PR
sleep 60
t app button shutter PR
sleep 10
poweroff yes
reboot yes

Note to user:
The Hero 3 must be set to come up in video mode for the above script to work.

Put the Hero 3+ in photo mode, wait 5 seconds, take one image, wait 5 seconds and power down
sleep 5
t app appmode photo
sleep 5
t app button shutter PR
sleep 5
poweroff yes
reboot yes

Installing a Script

When generating a script, verify that the text (or hex) editor is capable of saving the file in Unix format. This means that there is only a LF after each statement (no CR’s). If saved with carriage returns, the scripts will not execute. The scripts need to be named autoexec.ash and saved into the root directory of the SD card.

Figure 3: Location of the autoexec.ash file on the SD card

USB Image/Video Transfer

This section covers the steps necessary to access the micro SD card housed in the GoPro Hero 3+ without the need to open the underwater SeeStar camera housing. The procedure outlined here also works for the Hero 3 cameras.

Items Needed:
SeeStar Camera Housing
Host Computer (with DB9 serial or USB to Serial adaptor)
SeeStar Test Cable
DC Power Supply (minimum 15V, 1A)
USB Cable (mini B to Type A)
Hyperterminal (or equivalent)

Note to user:
The GoPro cameras and the host computer may have USB compatibility issues. Some USB 3.0 enabled ports on computers will not work with the GoPro cameras. Also, excessively long USB cables may prevent proper USB handshaking to occur. If USB handshaking is not achieved, try a different physical USB port or a different computer.

Step 1: Gather all required items.

Figure 4: SeeStar camera housing

Figure 5: USB-Serial adaptor

Figure 6: SeeStar test cable

Figure 7: DC Power supply

Figure 8: Mini-B to Type A USB cable

Step 2: Setup the DC Power Supply

The voltage range for the SeeStar System is 12Vdc to 22Vdc. A safe operating voltage is 18Vdc. Set the current limit to at least 1 amp.

Figure 9: Configuring the DC power supply

Step 3: Connect the SeeStar Test Cable.

Plug the power connectors (red positive and black return) into the DC power supply. Plug the DB9 connector into your USB-Serial adaptor (gender changer may be necessary). The two spare pins are currently not used, leave them aside.

Figure 10: Powering the SeeStar camera module

Step 4: Verify serial communication

Open up a hypterminal window. Start a new session using the correct COM port. The serial settings for the SeeStar camera module are 9600, n, 8, 1, no flow control. After applying power from the DC supply, a splash screen should appear. Typing Help All lists all of the available commands. Turn off the DC power supply once serial communication has been verified.

Figure 11: Welcome splash screen

Figure 12: Help All command listing

Step 5: Connect the USB cable to the SeeStar camera module

The type B USB connector is located behind the water tight SAE port. Remove the SAE fitting and attach the USB cable.

Figure 13: Camera endcap with SAE fitting

Figure 14: Camera endcap showing USB connection

Figure 15: Downloading images via USB

Step 6: Plug the USB cable into the host computer

As stated before, use a USB 2.0 port and if not successful, try an alternate USB port.

Figure 16: USB cable in computer

Step 7: Establish USB handshaking

Turn on the DC power supply. The splash screen should appear. Type PWR ON. This command passes the 4.2Vdc GoPro battery voltage to the camera, but does not turn it on.

Figure 17: PWR ON command

Wait 10 seconds and type CAM ON. This command mimics a human pressing the physical ON button on the GoPro Hero 3+.

Figure 18: CAM ON command

At this point, the camera should turn on, and USB handshaking should initiate. The LCD screen on the Hero 3+ will display the USB transfer symbol.

Figure 19: USB transfer indication on Hero 3+

The host computer should recognize the Hero 3+ as a USB device.

Figure 20: Opening an SD card

The user can now open a new Windows Explorer folder and navigate down to the Hero 3+ pictures and/or videos for transfer to the host computer and deletion from the SD card.

Figure 21: File listing of SD card