Serial Interface
RockREMOTE Mini and Mini OEM provide a physical serial interface for local device control, configuration, firmware maintenance, positioning data and Iridium Messaging Transport (IMT) messaging.
Connect the serial interface​
RockREMOTE Mini​
Use the 12-way Power, Serial and GPIO cable. See the connector pinout and wiring table, or the installation guide when planning a permanent installation.
RockREMOTE Mini OEM​
The OEM product exposes the serial interface through its 30-way header. Refer to the Mini OEM pinout and electrical interface notes before designing or connecting an interface board. The Mini OEM pinout is different from the RockBLOCK Pro OEM pinout.
Default settings​
| Setting | Default |
|---|---|
| Interface mode | RS232 |
| Baud rate | 115200 |
| Data bits | 8 |
| Parity | None |
| Flow control | None |
The physical port can be changed to a supported RS4XX mode or another baud rate in user.cfg. See Serial Communication in the RockREMOTE Mini User Configuration guide.
Use the serial interface​
- Use the shared AT command reference for device control, configuration, positioning and IMT messaging.
- Follow the firmware and configuration update process when transferring firmware or configuration files over the physical serial port.
- Configure GNSS NMEA forwarding in the User Configuration guide.
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.
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:
- Session ramp-up: approximately 5 seconds to establish a session with the satellite network.
- Transmission: the time taken to send the data, which increases with the amount of data.
- Gateway to cloud: the time taken for the data to travel from the Iridium gateway to its destination.
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.