Smart Lamp Locator

Digital cap lamp devices and embeddable modules with RTLS, gas sensors, LTE-WLAN connectivity and other IoT features. Ready to be used in real-life mining environments.

Embeddable RTLS-IoT Modules for Lamps

ATEX and non-ATEX modules to enable 3rd-party mining equipment with advanced RTLS and IoT features. Such modules are available in three versions:

Interfaces

Interface	Notes
Offline-online RMA	position against matchpoints on the portal map
Modbus RTU	main interface to the cap lamp controller — native or third-party
Gas measurement	methane and CO, per the fitted sensor option
Gas alarms	MethaneALM, COALM
SOS	/OutSos with server acknowledgement
Two-way text messaging	/InSms to the lamp display, with delivery and read receipts
Environment telemetry	temperature, pressure, height
Proximity alerting	group, beacon ID and distance
Buffered upload	/BufferedData, ECO mode
Remote configuration	config and GATT access over MQTT
Heart rate	/HrsData
RFID	Em-Marine serial in the battery compartment

The table above describes the Wi-Fi variant, which is the baseline. Every variant reaches the lamp’s gas sensors, buttons and display over an internal Modbus RTU bus — the sensors belong to the cap lamp controller, and their readings arrive over that bus rather than being wired to the module. No CAN or RS-485 controller is fitted on any of them.

What differs between the three versions is the positioning radio and the uplink:

Version	Positioning	Server uplink
ATEX Locator: Wi-Fi Version	Offline-online RMA over BLE — nRF52	Wi-Fi — CC3100
ATEX Locator: UWB	UWB TWR and UWB TDoA, plus CAS-PDS	none of its own — a 2×2 cm add-on alongside a locator
Locator: LTE Version	Offline-online RMA over BLE — nRF52	LTE — nRF91

MQTT topics

The module reports about itself, publishing under its own LocatorID in the <prefix>/Locators/ tree. DeviceType is bler.

It shares /RTLS and /BufferedData with the rest of the line — see MQTT. The remaining suffixes are specific to this module and to underground mining use cases; no other device model publishes or accepts them:

Topic	Direction	Content
/RTLS	device → server	position, gas readings, environment, battery, status
/BufferedData	device → server	records stored while offline
/OutSos	device → server	SOS or gas alarm, with the readings that accompany it
/InSms	server → device	alarm banner or text message for the lamp display
/InSmsAll	server → device	the same, broadcast to every lamp — no locator segment
/OutAck	device → server	delivery and read receipts
/InAck	server → device	SOS acknowledged by the operator
/ConfigReadData, /ConfigWriteData	both	remote configuration
/GattRead, /GattWrite	both	remote GATT characteristic access
/HrsData	device → server	heart rate
/Timestamp	both	time synchronisation
/TLM	device → server	beacon telemetry

Gas measurement and alarms

Gas sensors are read over Modbus and reported in the position payload. Each gas has a measured value and a separate alarm flag, so a reading and a threshold breach are distinct facts:

Key	Meaning	Format	Unit
Methane	methane concentration	decimal, two places	percent by volume
MethaneALM	methane sensor status word	integer	—
CO	carbon monoxide concentration	integer	ppm
COALM	CO sensor status word	integer	—
Pressure	barometric pressure	integer	pascals
LocatorTemp	temperature	decimal, one place	degrees Celsius

The two gases are scaled differently — methane carries two decimals, CO is a whole number — and neither carries its unit in the message.

A gas reading is not always a number. When the sensor does not answer, the device emits the JSON string "-.--" where the value would be:

"Methane": 1.35     sensor answering
"Methane": "-.--"   sensor not answering

A parser that assumes a numeric type fails on exactly the messages that matter most. Check the type before converting, and treat the string form as no reading rather than as zero.

MethaneALM and COALM are the sensor's raw status word, not booleans, and they split by byte: the high byte reports sensor health, the low byte the threshold state. Test value & 1 for the alarm and read value >> 8 for health — comparing the whole word to 1 fails on a sensor that is merely warming up. Codes are on Gas Sensors.

Which keys are present depends on the fitted sensor option, recorded in the SL_CONFIG characteristic (0x8308) at manufacture:

Value	Fitted sensors
0	none
1	methane
2	CO
3	methane + CO
4	methane + pressure + temperature
5	CO + pressure + temperature

An integration reads SL_CONFIG rather than assuming a sensor is present: an absent key and a zero reading are different facts.

SOS and message flow

SOS

The wearer raises an SOS from the lamp button. The device publishes on /OutSos a message that combines position, the SOS flag and the gas readings current at that moment, so an operator sees where, what and how bad in one message. SOS stays 1 while the alarm is active; the wearer clears their own SOS with three presses of the button. Operator acknowledgement arrives on /InAck.

Alarms and text messages to the lamp display

Both directions of display messaging use /InSms, and the key selects the presentation:

{"ALM": "Evacuate section 4"}       alarm banner
{"SMS": "Report to the shift lead"} plain text message

The text is capped at 140 characters. If something is already on the display, the new message is queued rather than dropped or overwritten. /InSmsAll — with no locator segment in the topic — broadcasts to every lamp on the site.

Receipts

Each message is receipted twice on /OutAck: once when it reaches the lamp (AckALM or AckSMS), once when the wearer has seen it (AckReadALM or AckReadSMS). All four flags appear in every receipt and exactly one is set to 1.

A receipt cannot be matched to a specific outbound message by ID. Its MessageID is the lamp's own outgoing counter, not an echo of anything the server sent — and /InSms carries no identifier for the device to echo. Correlate by lamp, flag and time; do not send a second message to a lamp while an earlier one is unreceipted if the two must be told apart.

Position and environment payload

The /RTLS payload combines the observed beacon with device and wearer state:

Key	Content
MessageID	the device's own outgoing counter
LocatorID	device identity
DeviceType	bler
BeaconID, BeaconMinor	observed beacon — BeaconID is byte-reversed
Distance, RawDistance	filtered and unfiltered distance
FilterType	filter applied to Distance
BeaconRSSI	received signal strength from the beacon
BeaconTemp, BeaconBattery	temperature and battery reported by the beacon
BatteryCharge	lamp battery state
Lamp_Status	lamp state
Methane / CO / Pressure / LocatorTemp	gas and environment, per SL_CONFIG
APRSSI	WiFi access-point signal strength
Activ_state, Accel_state, Time_in_sleep	charging / activity state and time spent inactive
Timestamp	message time, milliseconds

The gas alarm keys are not in this payload. MethaneALM and COALM appear only on /OutSos. A position message carries the reading; the alarm state arrives with the SOS.

Proximity alerting

The module alerts on approach to a designated beacon. It is governed by three configuration parameters — they are read and written through /ConfigReadData and /ConfigWriteData, and do not appear in position messages:

Parameter	Content
PROXIMITY_GROUP	group being monitored
PROXIMITY_BEACON_ID	beacon to watch for
PROXIMITY_DIST	trigger distance

The configuration response also carries HEIGHT, EM_MARINE_SN (the RFID serial in the battery compartment), SL_CONFIG and the network, filter and blink settings — all of it configuration state rather than telemetry.

Offline operation and ECO mode

The module records position and telemetry without network coverage and uploads on /BufferedData when a connection returns — see Offline-online RMA. In ECO mode the device remains offline for a configured interval before connecting, set by the sleep-duration parameter.

GATT ranges

The module uses the 0x81xx / 0x82xx / 0x83xx vendor ranges rather than the 0x51xx UWB service:

Range	Contents
0x81xx	network configuration — WI_FI_NAME, WI_FI_PASS, SRV_ADDR, SRV_PORT, NTP_SRV_ADDR, PREFIX, LocatorID
0x82xx	status — FIRMWARE_VER, BLE_MAC, WIFI_MAC, IP
0x83xx	RTLS configuration — SL_CONFIG, RTLS_MIN_DIST, RTLS_MAX_DIST, FILTER_TYPE, BLINK_ENABLE, BLINK_INTERVAL, SLEEP_DURATION_M, proximity settings

All of these are also reachable remotely over MQTT through /ConfigReadData and /ConfigWriteData, and individual characteristics through /GattRead and /GattWrite.