HYDROMEA Luma X User manual

a fast, long-range, optical underwater communication system
Manual
Version 1.8 for Firmware Version 1.4
9/2023

2 LUMA X 9/2023
Contents
1 Introduction ............................................................................................................................ 4
2 Initial setup ............................................................................................................................. 4
2.1 Windows 10 setup ............................................................................................................ 5
2.2 LUMA X setup ................................................................................................................... 6
2.3 Setting the IP address ....................................................................................................... 7
2.4 Testing the communication ............................................................................................. 8
2.5 Transmitting data ............................................................................................................. 9
3 Modem configuration ............................................................................................................. 9
3.1 Main page ....................................................................................................................... 10
3.2 Parameters page ............................................................................................................ 10
3.3 Status page ..................................................................................................................... 14
3.4 IP address change page .................................................................................................. 16
3.5 Communication test ....................................................................................................... 16
4 Modem firmware upgrade using LumaConf ......................................................................... 17
5 Maintenance ......................................................................................................................... 19
6 API ......................................................................................................................................... 19
6.1 API parameters ............................................................................................................... 19
1.1 API usage examples using Python .................................................................................. 25
7 Electrical and software Characteristics ................................................................................. 26
8 Mechanical Characteristics ................................................................................................... 27
9 Errata ..................................................................................................................................... 29

3 LUMA X 9/2023
WARNING:
 bright LED light source, do not look directly at emitter
 a few people may experience epileptic seizures when
viewing flashing lights

4 LUMA X 9/2023
1 Introduction
The LUMA X is an optical modem for fast, reliable wireless underwater communication. Each
LUMA X is a full transceiver and thus capable of half-duplex communication (transmission and
reception).
Note: this manual applies to the LUMA X as well as the LUMA X-UV. Throughout the manual
all references to LUMA X also apply to LUMA X-UV except for when there is an explicit
differentiation.
Note: this manual is only valid for the v1.4 firmware version of the LUMA X modem. You can
check your firmware version on the main webpage of your modem (see chapter 0 of the
manual to access the LUMA X webpage). If your modem firmware is outdated, please contact
Hydromea in order to get the latest version of the LUMA X firmware.
2 Initial setup
Note: while submerging the LUMA X, a small number of bubbles may come out of the
pressure compensation vent at the connector end of the modem. When LUMA X is back on
the surface a small amount of water may come out of the vent.
For normal operation of the LUMA X, only the Ethernet cable is used for the communication.
The serial cable is only used for factory reset and firmware upgrade of the modem.
The LUMA X comes preconfigured to forward data, automatically select the transmission speed
and the amount of LEDs used for transmission depending on the distance between the modems
and the amount of ambient light. They do not require configuration for normal use, however
this setup guide will allow you to check if the optical communication link is well established and
enable you to change the configuration of the modem if necessary.
Note: As the LUMA modems form a bridge, they should not be connected to the same cabled
network (i.e. do not plug both modems into the same switch). Doing so may lead to a loop in
the network, where one LUMA picks up traffic from the other LUMA and feeds it back to the
switch, flooding the network with packets. The modems should be connected to two separate
cabled networks as shown in Figure 1.

5 LUMA X 9/2023
Figure 1: Typical initial test setup. The IP addresses of the modems are not critical but useful to differentiate them
2.1 Windows 10 setup
The following steps explain how to set an IP address on your Windows 10/11 PC
 go to → Settings → Network & Internet → Ethernet (in left column) → Network and
Sharing Center (in right column) → Change adapter settings (in left column) → right click
on Ethernet adapter → Properties → select Internet Protocol Version 4 (TCP/IPv4) →
Properties
 set the address as shown in Figure 2
Verifying the IP address setting:
 Open a command line: → Windows PowerShell
Figure 2: Windows 10 network settings

6 LUMA X 9/2023
 Type: ipconfig /all
 You should see the IPv4 address setting shown in Figure 3
Figure 3: IPv4 address settings
On the remote PC, repeat the procedure, but set the IP address to 192.168.102.103.
2.2 LUMA X setup
Once the host computer’s IP address is set correctly the connection to the LUMA X can be
tested.
 Connect only one LUMA X to a computer via an Ethernet connection using Hydromea’s
power/data cable.
 Connect the LUMA X to a suitable supply voltage (12 V – 36 V) using Hydromea’s
power/data cable.
 Optional step: to test that the IP address has been set correctly, the computer should
now be able to ping the LUMA X on its default IP address 192.168.102.101 and the
modem should respond to it.
o Windows 10: Open a command line: → Windows PowerShell
o enter ping 192.168.102.101
 Open a browser, and enter 192.168.102.101 into the address field. The LUMA X web
interface main page should appear (see Figure 5)

7 LUMA X 9/2023
All LUMA X have their IP address factory-set to 192.168.102.101.
You can change the IP address of the modem through the web interface.
2.3 Setting the IP address
For the initial test, modem (1) can remain at the default IP address. The other modem (2) must
be set to a new IP address that is unique within the subnet. For the initial example, we use
192.168.102.102.
 Plug in only modem number (2) and navigate your browser to 192.168.102.101
 Click on the menu item “IP change”
 Enter the new IP address 192.168.102.102 (for the second modem)

8 LUMA X 9/2023
 Click “Set”. The new IP address is now temporarily applied, and the page will reload
showing the new IP address:
 To store the new setting to flash memory, click “Save”. The modem is now set to the
new IP address.
2.4 Testing the communication
To test communication by exchanging messages between modems, the modem’s firmware
provides a simple interface as shown in Figure 4. Connect the first modem to the operator PC,
and connect the second modem to a remote PC (e.g., a second laptop, or an ethernet-capable
remote device). The operator PC should be set to IP address 192.168.102.100. The remote PC
should be set to IP address 192.168.102.103 (this IP address is given as an example for the
initial setup – it can be chosen freely within the same subnet).
Power up the modems on both sides. The boot-up takes up to 10 seconds.
Access the “Comm. Test” page from the operator PC,
http://192.168.102.101/test_comm.html
and from the remote PC,
http://192.168.102.102/test_comm.html
Messages can be exchanged from one modem to another and should be displayed on the page.
Note that ambient light, artificial light sources (fluorescent office lighting, LED lamps, screens,
sunlight) may interfere with the optical channel and disrupt communication. If a link cannot be
established, try to turn off lights, or cover the modems with an opaque sheet of cardboard or
cloth while ensuring line of sight between the modems. Ideally the modems should be
separated by at least 1 meter, as the receivers may saturate at very close range.

9 LUMA X 9/2023
Figure 4: messaging interface for modem-to-modem communication
2.5 Transmitting data
On the operator PC, open a Shell, and type:
ping 192.168.102.103
If everything is configured correctly, the modems will visibly flash with blue light, and the ping
will show the response from the remote PC.
The optical link is now ready and will forward any ethernet traffic from one side to the other
side.
3 Modem configuration
This chapter will describe the modem configuration in detail.
LUMA X modems come preconfigured allowing for easy optical communication and do not
need additional configuration.
However, for more specific use cases, where limiting the number of LEDs used for transmission
or limiting the modem to a specific optical speed, these can be changed in the “Parameters”
section of the LUMA X web interface.
The web interface is also useful to get some statistics about the modem itself, such as the
throughput, number of packets received and lost as well as the supply voltage of the modem.

10 LUMA X 9/2023
3.1 Main page
Figure 5: main page of the web-based configuration-UI
This page provides information about the current revision of the hardware, firmware and API. It
also provides the firmware’s SHA and the unique processor ID.
3.2 Parameters page
Figure 6: parameter page of the web-based configuration-UI

11 LUMA X 9/2023
This is the main configuration page for the LUMA X. Hovering over the “?” next to each
parameter provides a short description.
Note: No change will become effective until the “Set” button has been pressed. After power-
cycling the modem, the parameters will revert to the previous setting. Pressing the “Save”
button will store the new set of parameters into the modem’s flash memory and make it the
new permanent set of parameters.
The factory set parameters are in bold
Default Start
State
Active
Config
The state which LUMA X will boot into after power-cycling.
The Config state should only be used for debugging or
configuration as the modems will not forward any data.
It allows the user to connect multiple modems on the same
switch without creating switching loops.
Auto-power
active
On
Off
On: the modems will adjust the number of LED banks used
based on the strength of the received signal and the ambient
light level.
Off: the modem will use the maximum number of LEDs
specified in Max number of active LEDs (below) except when
it is in overheat mode.
Max number of
active LEDs
1
2
3
4
5
The maximum number of LED banks the modem can use.
If Auto-power active is On, it will automatically select the
optimal number of banks while not going above the number
of LED banks specified her.
If Auto-power active is Off, the modem will always use the
number of LED banks specified her.
Limiting the maximum number of active LED banks will
impact the maximum range, but will reduce the power
consumption as well as the amount of light generated by the
modem.
If the modem is used outside the water and starts to
overheat, it will automatically decrease the number of active
LED banks in order maintain a safe temperature (< 60°C)

12 LUMA X 9/2023
Auto-speed
active
On
Off
On: the modems automatically negotiate the optical speed at
which they should communicate.
If the modems are close to each other or there is a lot of
ambient light variation, the modems may switch their speed
often and it can vary between 1Mbits/s and 10Mbits/s, which
can be undesirable. In this case set the auto speed to Off.
This parameter should be set to the same value on both
modems.
Optical speed 1 MHz
2 MHz
4 MHz
6 MHz
8 MHz
10 MHz
In case Auto-speed active is set to Off, the optical speed used
for data transmission can be set manually.
A higher optical speed means less range and less resilience to
optical noise and ambient light.
This parameter should be set to the same value on both
modems.
Encoding On
Off
On: increases the link quality, decreases throughput
Off: decreases link quality, increases throughput.
Note: the improvements of the link quality from through
encoding are minimal for now, but this is an area of the
LUMA X modem under heavy development and may be
improved in the future.
Auto gain
control
On - with
sensitivity
autoselect
On - fixed
sensitivity
Off
On - with sensitivity autoselect: The LUMA X will adapt to the
ambient light level by changing the receiver gain and
sensitivity.
On - fixed sensitivity: should be done in case of troubleshoot
and debugging
Off: should be done in case of troubleshoot and debugging
Manual gain
value
0-2800
(500)
This sets the receiver gain

13 LUMA X 9/2023
if Auto gain control is On, the current gain value is displayed,
but cannot be changed.
if Auto gain control is Off, it is a mutable parameter
Receiver
sensitivity
On
Off
In case the Auto gain control is Off or On - with fixed
sensitivity, this is a mutable parameter.
Setting the Receiver sensitivity to On will increase the
modem’s light sensitivity. This will increase the
communication range, but make it more susceptible to
ambient light or optical noise.
If Auto gain control is On - with sensitivity autoselect, the
modem will decide itself when it needs to go to high or low
sensitivity.
Manually changing this value should be left for
troubleshooting.
Table 1: parameters within the web-based configuration UI

14 LUMA X 9/2023
3.3 Status page
Figure 7: status page of the web-based configuration-UI
This page provides information about the current status of the LUMA modem and is updated
once every second. For all data rates (throughput, packet CRC errors, received and loss), three
values are displayed: per second, per minute and total since the start of the modem.
Current optical speed Optical speed used by the modem, in case Auto-speed active is On,
this value may change.
Temperature LUMA Temperature (in degrees Celsius) of the optical transceiver. When
the modem gets too hot, it will reduce the number of LED banks it
uses to avoid overheating.
Gain Gain value of the receiver. A high gain value indicates that the
modems are far apart and in darkness, a low gain value indicates
that the modems are close to each other or that there is a high
amount of ambient light.

15 LUMA X 9/2023
Number receivers
active
(1 .. 4)
the number of receivers the modem is using (the sensitivity) to
detect light pulses
LUMA voltage supply voltage of the modem
LUMA voltage
(min over last
minute)
minimum value of the supply voltage observed over the last minute.
This is useful to detect an input voltage drop
Noise amplitude
(0 .. 255)
Amplitude of the noise the modem observes.
Signal strength
(0 .. 255)
a metric indicating the strength of the signal received
Signal amplitude
(0 .. 1024)
Metric indicating the amplitude of the pulses received
Signal to noise ratio
(0 .. 255)
Signal to noise ratio Metric, using the noise amplitude and the signal
amplitude.
Throughput received
[kbps]
Average data rate for data received
Packets CRC errors Number of packets discarded in last second due to CRC error
(indicator for the stability of the link)
Packets received Number of error-free packets received within the last second
Packets lost Number of packets lost within the last second between successfully
received packets.
Note: if no packet is successfully received, lost packets cannot be
tracked.
Table 2: modem and link information provided by the web-based configuration UI

16 LUMA X 9/2023
3.4 IP address change page
Figure 8: IP-setting page of the based configuration-UI
This page lets you modify the IP address of the web-based configuration interface (which you
are using right now). The current IP address of the of the web-based configuration interface is
displayed and can be changed. Changing the IP address and pressing Set button will
immediately change the IP address, however this change is not permanent and the change
would be reverted during a power-cycling. After pressing Set button, the webpage will try to
reconnect to the web-based configuration interface using the new IP address. After reloading
the page, the new IP address will be shown and a Save button is available. Pressing the Save will
store the new IP address in the modem’s flash memory, thus making the change permanent.
Figure 9: saving the IP address to flash in the web-based configuration-UI
3.5 Communication test
In order to test the modems’ communication capability without using any additional tools apart
from a web browser, we added a communication test page, which allows the user to send text
messages to the other modem, which will display the message on its respective communication
test page.
This tool can be used to ensure that the modems can communicate in case parameters are
changed or when testing in a difficult environment, such as in a high ambient light.

17 LUMA X 9/2023
4 Modem firmware upgrade using LumaConf
The LumaConf software allows you to communicate with the modem using the serial cable
which can be used for resetting the settings, or do a firmware upgrade of the modem.
It is available here:
https://files.hydromea.com/luma/LumaConf_lumaX.zip
In order to upgrade the firmware of LUMA X or carry out a factory-reset, LUMA X must be put
into Bootloader mode. The following steps will upgrade LUMA X firmware and/or carry out a
factory reset:
 Start LumaConf
 Ensure that the LUMA X is connected to a computer through the serial connection. This
is most easily achieved by using Hydromea’s power/data cable-box which provides a
serial connection through a USB-to-serial conversion within the power/data cable and
can be accessed via a micro-USB port.
 Ensure that the LUMA X is connected to a power supply
 In LumaConf set Interface to the correct serial port
 Click on Firmware update within LumaConf. This will open the Bootloader dialog box
(see Figure 10).
 Cycle the power for LUMA X
 The user now has a few seconds after start-up to discover the LUMA X by clicking the
Discover button. Once it appears in the Devices window, the LUMA X will stay in
bootloader mode and more options will be available to the user.
o Firmware update+factory reset: select the proper firmware file by clicking on
Select … and then start the update by clicking on Write Flash. Wait for the
progress bar to reach 100%. After a firmware update a factory reset will also be
carried out automatically.

18 LUMA X 9/2023
Note: please make sure that you select the proper firmware image, the last
digits of the filename LX########## need to match the serial number
engraved on the modem.
o Factory reset only: clicking on Clear Settings will factory reset all LUMA X
settings.
 Clicking on start Application will cause the attached LUMA X to exit the bootloader and
restart. The LUMA X will restart in config mode as a firmware update will also cause a
factory reset which sets the Default state after reboot to config.
 Closing the bootloader window and selecting Ethernet in Interface will then lead to the
LUMA X showing up in LumaConf.
Note: a limited set of options is available in the Bootloader menu when one or multiple
LUMA X is/are connected via Ethernet and in config mode. In this case the Bootloader
window will list all LUMA X connected to the network with their last IP byte as an index.
The only available actions in this mode are reading the unique serial number of a LUMA X
by clicking on Get Info which then shows the serial number in Processor ID or to soft reset
the attached modem(s) by clicking on Reset.
Figure 10: Bootloader section of LumaConf for upgrading the firmware or factory reset of LUMA X

19 LUMA X 9/2023
Discover Query and display all connected LUMA X.
Reset all Reset all connected LUMA X
Get info Retrieve the processor ID of the selected LUMA X
Firmware (only in serial) selects the firmware cfi file for upgrade
Write
Flash
(only in serial): Programs the firmware to the LUMA X. It is completed once the
transfer progress bar reaches 100%. In case of transfer error, the bar will regress
to 0%
Clear
settings
(only in serial): Will factory-reset the parameters on the LUMA X, such as its IP
address and the config/active mode into config.
Start
application
(only in serial): Will start the LUMA X. Note: power cycling the LUMA X and
closing the Firmware upgrade window will not put LUMA X into bootloader
mode and it will start normally as well.
5 Maintenance
Please wash the modem with warm water (only) to remove any built-up which could negatively
affect its operation. Apply a thin film of silicone grease to the rubber part of the connector pins
to protect the connector and to facilitate mating. For maintenance details regarding the
connector follow SubConn's instructions.
6 API
Hydromea provides an API, based on REST, with which key operating parameters of the LUMA X
can be changed or status parameters retrieved while the modem is running. The following
tables provide a complete list of these parameters, followed by examples showing how to
retrieve and change them (in case they are writable). The examples are written in Python.
6.1 API parameters
status.json (read only)
Parameter Description
amplitude Current amplitude value of the Luma, selected by the auto gain
ambient Ambient value read by the Luma sensor
temperature Current temperature of the Luma
throughput_received
_sec
Data received successfully by the modem in bits per seconds

20 LUMA X 9/2023
crc_errors_sec Number of CRC errors that happened in the last second in the Luma.
A high number could indicate some noise or
that the Luma is at the edge of the maximal range
pkt_recv_sec Number of packet received in the last second
pkt_loss_sec Number of packet lost in the last second. Note that the Luma can only
detect packet loss after it has received a
packet out of sequence
throughput_received
_min
Data received successfully by the modem in bits per seconds over the
last minute
crc_errors_min Number of CRC errors that happened in the last second in the Luma.
A high number could indicate some noise or
that the Luma is at the edge of the maximal range
pkt_recv_min Number of packet received in the last second
pkt_loss_min Number of packet lost in the last second. Note that the Luma can only
detect packet loss after it has received a
packet out of sequence
throughput_received
_total
Data received successfully by the modem in bits per seconds over the
runtime of the modem
crc_errors_total Number of CRC errors that happened in the last second in the Luma.
A high number could indicate some noise or
that the Luma is at the edge of the maximal range
pkt_recv_total Number of packet received in the last second
pkt_loss_total Number of packet lost in the last second. Note that the Luma can only
detect packet loss after it has received a
packet out of sequence
gain Current gain value of the receiver