satlog Modem
The satlog.io modem contains the Iridium modem, antenna and GNSS capabilities for fast and accurate position data and connectivity around the globe. All aspects of communicating on the Iridium network and with the satlog.io cloud is handled by the modem making it very easy to adopt to any project capable of communicating with serial/UART.
The modem can also run in standalone mode as a pure asset tracker by simply providing power as its simplest operation mode.
Connectivity & Electrical
Interface pinout
Only 4 pins is necessary to control and power the satlog.io modem making it ideal for waterproof connectors or simple field termination like RJ11.
Pin 2-5 of RJ11 is used with the Data Logger.
| Pin # | Name | Description |
|---|---|---|
| 1 | 9-36V | 9-36VDC supply1 |
| 2 | 5V | 5VDC supply, minimum 1A |
| 4 | Ground | Ground supply |
| 4 | RX | To receive serial data from the modem |
| 5 | TX | To send serial data to the modem |
Serial port configuration for RX/TX interface:
| Setting | Value |
|---|---|
| Baud Rate | 9600 |
| Bits | 8 |
| Parity | None |
Eletrical Characteristics
| State | Current Draw |
|---|---|
| InitState | 500mA2 |
| IdleState | 100mA2 |
| SendState | 200mA2 |
| SleepState | To be implemented |
Serial Interface
Any integrator can interface with the modem to queue data for sending and forwarding to your API/backend if the modem is only needed for sending data or obtaining time/position.
Data can be sent using the simple QUEUE command and transmission, re-delivery and all Iridium policies are handled by the modem.
QUEUE command
Format:
QUEUE,<payload length>,<payload-hex-bytes>\r
Example:
QUEUE,5,68656c6c6f\r
hello
The QUEUE command is used to transmit a payload (recommended max 100 bytes) to the modem for transmission. Status of transmission will be reflected in MODEM and can take several minutes. Several messages can be queued for transmission, but it's important that you stay within your monthly data volume to avoid overage charges. The satlog.io team will work with you to validate a solution before large scale deployment.
READ command
Format:
READ,<mt msg id>\r
Example:
READ,43\r
After receiving a message (see MODEM_IN), the message has to be marked read using the READ command. The <mt msg id> parameter is from the <msn> field of the MODEM_IN message.
MODEM_CIEV message
Format:
MODEM_CIEV,service=<service available>,signal=<signal level>
Example:
MODEM_CIEV,service=0,signal=3
The MODEM_CIEV message indicates reception. The service field will indicate if the modem currently has locked on to a passing satellite and would attempt a transmission. The signal field indicates signal level / bars between 0 and 7.
MODEM message
Format:
MODEM,state=<modem state>,power=<power>,net=<net>,signal=<signal>,attempts=<attempts>,queued=<queued>,voltage=<voltage>
Example:
MODEM,state=InitState,power=1,net=1,signal=0,attempts=0,queued=0,voltage=5.0
The MODEM message holds the modem state, indicating which state the modem is operating in (<state>), signal state (see also MODEM_CIEV). <attempts> holds number of transmission attempts for the current message and <queued> holds the backlog of messages to send.
QUEUE message
Format:
QUEUE,messages=<queued messages>,bytes=<bytes queued>
Example:
QUEUE,messages=1,bytes=5
The modem details message describes the current data in the outgoing queue, number of payloads (<queued messages>) and the total size of these in bytes (<bytes queued>).
GPS message
Format:
GPS,ts=<epoch seconds>,lat=<latitude>,lon=<longitude>,speed=<speed ms>,track=<track>
Example:
GPS,ts=1738355093,lat=48.077164,lon=16.450058,speed=0.000000,track=0.000000
The GPS message has GNSS status & information. The ts field holds seconds since epoch (UTC) from the GNSS constellation and will have a very high accuracy. lat and lon fields holds the latitude and longitude of the device in decimal degrees (DDD.DDDDDD), western and southern hemisphere is indicated by negative values (-65 for 65° west, -23 for 23° south respectively). speed field has the last speed over ground between positions in meters per second. track holds courde over ground in degrees.
MODEM_IN message
Format:
MODEM_IN,msn=<mt msg id>,msg=<payload>
Example:
MODEM_IN,msn=43,RELAY_ON
MODEM_IN carries an incoming mobile terminated (MT) message to the modem/equipment. An incoming message needs to be marked read to clear the incoming queue. The <mt msg id> is used with the READ command.