I’ve been trying to get the sprkfun lora serial radios to transmit rtcm correction data from my facet to multiple rovers. Evedently the default airspeed is to slow because the age on my rtk surveyors starts out at about 1-2sec, then jumps up to 10sec, then it starts only getting a correction every min and in the meantime the radios act like they reboot. My RFD900+s work perfectly, 0 to 1 on the age, i just need multi point capability now. I’ve been trying to figure out how to get the airspeed faster but ATW doesn’t seem to save the settings. When I cycle the power, all related airspeed settings revert back to default. Is there another way to save the settings? Thanks
Did you reboot (ATZ) after using ATW to write the settings?
I had a similar experience a couple weeks back. It was my first field test of the LoRaSerial radios with my RTK Facets. The latency jumped around like you experienced, and the RTK fixes were erratic. I had a couple folks waiting on me, and I had no time to experiment. So I yanked the LoRaSerial radios, attached my RFD900x radios, and everything worked perfectly.
The LoRaSerial radios worked with my Facets at home when I tested, the latency was 1 second or so, and the RTK fixes were solid. I was probably seeing fewer satellites at home, so my theory is the RTCM overwhelms the default factory airspeed of 4800 (according to the Sparkfun docs) went I’m out in the open seeing 30-40 satellites. My commercial GNSS equipment compresses the RTCM stream, and I do not believe the Facets do any compression on the RTCM.
When I query the radio settings (ATR, AT-?) the air speed is reported set to 0. I don’t know what a value of zero means; couldn’t find it in the docs.
I’ll try setting the airspeed to 9600 or higher the next time I’m heading out into the field.
Yes, I believe i tried that. I’ll try it again though. I have it working fairly good. Every once in awhile i loose it for about 30sec while the rssi lights flash real quick for a bit and then it gets reconnected and i have 0to2sec again. What i eneded up doing was hooking it to the computer, changing the airspeed to 9600, hooking the data port to the facet, then unpluged the laptop, that way the radio never turned off. Then did the same with the 2 radios connected to the rtk surveyers. I think im going to bump it up to 19200 and try it yet.
So yes, I’m convinced that the default airspeed of 4800bps isn’t sufficient for RTCM. Sparky did say somewhere in these forums that to use the 4800bps airspeed on the LoRaSerial radios, one would need to be careful with the RTCM data messages in use.
I think 9600bps would be sufficient.
All the above is transmitting the RTCM from the base to the rover at 1Hz.
How do you change the rtcm data output rate? My gnss measurement rate is at 1hz. Is that the rate I need to change? I tried the airspeed at 19200 this morning, and it still lost corrections a few times, for a bit. And I don’t believe it was distance issues because i was fairly close.
There are a set of parameters for the base rates. I recall that, when in base mode, the GNSS measurement rate is fixed at 1Hz. However, the wonderful folks at SparkFun updated the firmware in April 2023 to allow the configuration of different message rates for the RTCM messages.
So there are two different things to keep straight when thinking about this:
First, the rate at which the GNSS chip (F9P) is measuring (calculating GNSS position solutions).
Second, there are individual “message rate” transmit settings for each RTCM message type the F9P supports.
Those two different rates work together to define the ultimate rate at which messages are transmitted. If the measurement rate is 1Hz, and a specific RTCM message rate is 4, then that specific RTCM message is transmitting 1Hz/4, or 0.25Hz, or once every four seconds. (I’m typing this all from memory, double-check me.)
The SparkFun folks also helpfully provided a “reset to low bandwidth link” easy button in the WiFi AP base configuration menu.
Here’s the issue/featurerequest that prompted this:
So I haven’t been able to make the Lora radios work with the kind of accuracy I need, between them going for 10sec without an update from time to time and it rebooting every once in awhile. The rebooting and not saving airspeed settings are frustrating. They do work well enough for surveying, just not for the fine control I’m trying to do. I figured out how to install the multipoint firmware on the rfd900s and have been using them. They sit at .8 to 1.2 sec, every once in awhile it’ll hit 2sec, all day long, never miss a beat. But the default airspeed is set at 64kbps. That seems to make enough difference in accuracy that I can work with it.
I keep going back to my RFD900 radios too. I also see the latency on the RTK solution going up to 10 or 20s when I use the SparkFun LoRa radios. The RFD900s just seem to work better and my latencies are always under 2 seconds.