LoRaSerial operating modes for RTK RTCM, and AT-operatingmode values.

GPS/GNSS Development Boards
1

The LoRaSerial documentation mentions two operating modes, Point-to-Point and Multipoint.

Which is the best mode for RTK RTCM data?

What is the correspondence between the operating modes and the numeric values for the at-operatingmode command?

My understanding from the documentation is that Point-to-Point does packet retransmission, and that Multipoint does not. For the RTCM link transmitting from an RTK Base to an RTK Rover, I presume packet retransmission is undesirable, as (a) the retransmissions would clog up the data link and (b) every second there’s a new (set of) data (and packets) that supercede the previous second’s data. The data get old quickly, so don’t bother retransmitting missed packets; and the receiver doesn’t even need to ACK/NAK.

The AT command documentation for AT-operatingmode says a setting of “1” is the default, “0” is the min, and “2” is the max. But it doesn’t say what numbers correspond to Point-to-Point and Multipoint.

Does 1 = Point-to-Point?

Does 2 = Multipoint?

What does 0 mean?

2

I submitted a issue ticket for the missing documentation of the numeric values, but I’d still like to know the recommended operating mode for RTCM please.

https://github.com/sparkfun/SparkFun_Lo … issues/584

3

Perfect, thanks toeknee!

The operating modes are defined here: https://github.com/sparkfun/SparkFun_Lo … ngs.h#L311

typedef enum
{
  MODE_MULTIPOINT = 0,
  MODE_POINT_TO_POINT,
  MODE_VIRTUAL_CIRCUIT,
} OPERATING_MODE;

0 is multipoint. 2 is something called Virtual Circuits which is like a mesh network that has not yet reached maturity in its development.

Multipoint is ideal for long range RTCM, with the down side of longer sync up times. So when I use the radios for Rover/Base, I use P2P mode by default. If I really need to push the range, then I’ll use Multipoint but this can lead to longer sync times because the remote units have to wait for the main unit to come back around in the hop table. P2P mode has much faster detection of link down, and re-establishment of the link.

4

I’ll get this added to the docs shortly.

5

Docs updated.