Help needed with LoRaSerial (enclosed) for RTK project

GPS/GNSS
1

I am using a pair of SparkFun GNSS Flex pHAT - ZED-X20P kits for GNSS-RTK base and rover. I got everything working nicely with NTRIP over WiFi, but that greatly limited my range.

I bought a SparkFun LoRaSerial Kit - 915MHz (Enclosed), SKU: WRL-20029, but I’m having throughput problems.

I am runing MultiPoint mode, sending RTCM3 messages 1006, 1077, 1097, and 1127 at 1Hz. My USB speed is set to 115200 baud and AT-AirSpeed set to 19200. I should be able to send up to 1743 bytes/sec.

In testing, I have been able to send about up to 1100 bytes/sec for 20 to 30 seconds before the send rate drops and messages don’t get sent. This often results in a serial error and I lose the connection.

The issue seems to be back pressure as described in the Product Manual – Hardware Overview. However, there is no explanation of how to work around the problem.

What are my options?

2

I think you have a few things to try - increase the air speed, increase the Bandwidth, decrease spreadfactor, increase timeouts/ACK, etc…there are several you can tweak and test to see here

For things like number of resend attempts it might help to raise or lower, depending

If you get a working set of settings for your situation feel free to post it/the results here

1 Like
3

Thanks for the reply.

My error. It’s working better now. I will do some more testing and follow up in the near future.

I went back to the Product Manual and read it again. I failed to property set the operating mode to Multipoint. I read that one radio must be designated as the Server radio, and confused the AT-Server command with the AT-OperatingMode command. I was only setting AT-Server to 1 on the base radio.

After setting AT-OperatingMode on both radios to 0, I am not seeing any dropped outgoing messages. My receiving radio is connected to my desktop computer indoors for testing, and about 50 meters from the base radio outside. I’m seeing a few CRC errors at the receiver, but receiving 80% to 85% of all messages sent over a one hour test period.

My next step is to run some field tests with the rover.

3 Likes