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Serial Interface

RockBLOCK Pro provides one physical serial interface and two USB Type-C virtual serial ports for local device control, configuration, firmware maintenance, positioning data and Iridium Messaging Transport (IMT) messaging.

Connect the physical serial interface​

RockBLOCK Pro ANT and SMA​

Use the 12-way Power, Serial and GPIO cable. See the installation pinout and wiring table.

RockBLOCK Pro OEM​

The OEM product exposes the physical serial interface through its 30-way header. Refer to the RockBLOCK Pro OEM pinout and integration notes before designing or connecting an interface board. The Pro OEM pinout is different from the Mini OEM pinout.

Default settings​

SettingDefault
Interface modeRS232
Baud rate115200
Data bits8
ParityNone
Flow controlNone

The physical port can be changed to a supported RS4XX mode or another baud rate in user.cfg. See Serial Communication in the RockBLOCK Pro User Configuration guide.

Use the serial interface​

Browse all RockBLOCK Pro AT commands →

important

AT commands, serial firmware updates and NMEA forwarding share the physical serial interface. Use one function at a time. In particular, disable NMEA forwarding before using AT commands or starting a serial firmware update.

Do not check signal strength before sending

The Iridium Certus 9704 and 9770 transceivers in RockBLOCK and RockREMOTE products are configured in firmware to transmit only when signal strength is at least 1 bar. Do not duplicate this check in your application. Do not delay, block or skip a transmission based on a signal reading; send the data and the transceiver will transmit it when conditions allow.

Signal readings remain useful for diagnostics, installation checks and monitoring.

Latency and cold starts​

Latency is defined as the time taken for a transmission to be sent from the Iridium transceiver to the end destination.

  • IMT messages: on Ground Control airtime, the end destination is Cloudloop. From there, messages can be API pulled or pushed/forwarded to your own systems.
  • IP data: Latency for IP data is measured per packet between the transceiver and the IP destination.

End-to-end latency of an Iridium transmission, whether an IMT message or IP data, consists of three stages:

  1. Session ramp-up: approximately 5 seconds to establish a session with the satellite network.
  2. Transmission: the time taken to send the data, which increases with the amount of data.
  3. Gateway to cloud: the time taken for the data to travel from the Iridium gateway to its destination.
Session ramp-up in practice

Approximately 5 seconds is the average session ramp-up time quoted by Iridium. In practice it depends heavily on signal strength and the antenna's view of the sky. Ground Control regularly observes ramp-up times of 5 to 12 seconds, and occasionally longer.

Session ramp-up applies only to the first transmission in a session. Further transmissions while the session is active are sent without this delay.

If no data is transmitted for approximately 15 seconds or longer, the satellite link closes. The next transmission then requires a new session (a cold start) and incurs the full session ramp-up time.

On Iridium Certus 9770 products, an active IP data session also reduces IMT delivery time. Where ring alerts are used, MT delivery takes approximately 2 seconds longer.

Latency in an active session and after a cold startThree bars of equal length, each divided into stages. Single transmission: a short session ramp-up, a long transmission, then a short gateway-to-cloud stage. Consecutive transmissions in an active session: one session ramp-up, then transmissions 1, 2 and 3 in sequence, then gateway to cloud; transmissions 2 and 3 are sent without session ramp-up. Cold start: session ramp-up, transmission 1 and gateway to cloud, then a period of approximately 15 seconds or more without transmission during which the link closes, followed by a new session ramp-up, transmission 2 and gateway to cloud.Session ramp-up (typically 5–12 s)TransmissionGateway to cloudLink closedSingle transmissionRamp-upTransmissionConsecutive transmissions in an active sessionRamp-upTransmission 1Transmission 2Transmission 3Transmissions 2 and 3 are sent without session ramp-upCold start after approximately 15 seconds without transmissionRamp-upTransmission 1Link closedRamp-upTransmission 2Transmission 2 requires a new session ramp-up
Source: Iridium partner proprietary document, from which valid information has been taken to be shared with the public.

Virtual Serial Interface​

Once the RockBLOCK Pro is connected via Type-C to an end device it will enumerate with two virtual ports.

On Windows the ports will show as any other COM* port, on Linux they will show as /dev/ttyACM* and on a MacOS they will show as /dev/tty.usbserial* or /dev/cu.usbmodem*

note

On Windows, com ports can be viewed in Device Manager or listed in Command Prompt (CMD) with mode
On Linux and MacOS, com ports can be listed in Terminal with ls /dev/tty*

The lower numbered VCP (Virtual Com Port) will use whichever AT interface is selected, and the RockBLOCK Pro will respond accordingly

The higher numbered VCP will display a Statistics page with useful information as can be seen below VCP Statistics page

On APNT hardware the Statistics page also displays the APNT position data, which can also be polled from the AT command terminal with AT+GNSS or AT+APNT.

APNT licence key​

On APNT hardware, the 28 character APNT Licence Key can be loaded over USB-C or the serial interface, as well as with Cloudloop Device Manager or the RockCONNECT IoT app (see APNT Licence Key).

File system over Type-C​

The File system (MSD - Mass Storage Drive) on the RockBLOCK Pro allows the enumeration of a folder named “ROCKBLOCK P” when connected over Type-C.

This file system allows the user to drag-and-drop or copy-and-paste a text file containing the APNT Licence Key, after a reboot the Licence Key will be loaded in.

In addition to the APNT Licence Key text file, the user needs to make sure there is a separate “manifest.txt“ file uploaded as well - containing the name of the APNT Licence Key text file that must be specifically named “APNT-Key.txt” and containing:

<APNT MODULE SERIAL NUMBER>
<APNT MODULE KEY>
Example manifest.txt

Example APNT-Key.txt

tip

Make sure that both files are uploaded and have followed the specified format, and after which reboot the RockBLOCK Pro by either removing the USB-C and re-plugging after 10 seconds or via the Reboot AT Command

AT+CMD over Serial (Physical and Virtual)​

The serial AT Command interface can be accessed over Physical RS232/RS485 connection with the provided Power, Serial and GPIO cable, or, via Virtual Com Ports over Type-C.

  • AT+APNTWK=<KEY> allows the user to enter a licence key where <KEY> is the licence key in question. i.e (AT+APNTWK=C5EXX2511RRR69W2ZMIT274V3111)
  • AT+APNTGS allows the user to read the APNT module Serial Number.
  • AT+APNTUK allows the user to restore the licence key.
danger

+APNTUK will erase the current APNT Licence Key and fallback to the previous one, in a case where there is only one APNT Licence Key loaded, running this command may result in losing the only Licence Key

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