I want to send RTCM correction messages from the (SKU: GPS-15136) base to rover via Xbee (SKU: WRL-15126). I achieve RTK fixed mode when using a wired connection, so I know the two F9P’s are correctly configured per Ublox’s Moving Base Application Note. I have tried without success to replace the wired connection between the base and rover with a WiFi link (ESP8266) but had no success. I am now trying a pair of Xbee’s as it appears that no code is required?
Per Sparkfun’s tutorial, I configured my two Xbee 3’s firmware to the legacy 802.15.4 protocol. I set the Xbee 3’s baud rate to the F9P’s, namely 115200. Other than change the PAN ID, I made no other changes to the XBee 3 default settings in XCTU. My two Xbee 3 modules are talking to each other via Sparkfun Explorer USB’s when I type in either XTCU console log.
My multimeter indicates about 3.3V at the F9P UART2 TX pin which outputs the RTCM messages. However when I connect this output to the Xbee 3 DIN pin, there is no data appearing on the XCTU console log. Also, no messages appear on U center’s UBX-RXM-RTCM monitor, as in the case of my wired connection.
Could you please help me set up this wireless link between the pair of F9P receivers.
I imagine at this point there is an issue with the byte package size the RTK2 jamming into the Xbee to send. I would suggest using a microcontroller as the middle man until you can pass functions to turn off certain features not needed until something is able to send in an acceptable packet size.
The base F9P is configured to send the minimum required 7 RTCM messages for RTK. This is done via the UART2 TX pin (per page 11 of Ublox’s Moving Base Application Note) to the DIN pin of the Xbee/Explorer USB board. I have also connected a F9P GND pin to a Explorer/Xbee GND pin. Your RTK2 Hookup Guide implies this set of RTCM messages are about 2000-3000 bytes per second (say 25 000 bits). This appears to be well within the Xbee3 (WRL-15126) specs of RF 250Kbps, Serial 1Mbps? The Xbee has many settings in XCTU that may require tweaking (such as receive and transmit buffers, or flow control threshold), but I have not been able to find out if this is required in this case?
Can you confirm if the Xbees send/receive data if there is a middle man micro-controller? like GPS-RTK2 → Arduino → Xbee. If that does send, then I would suspect that there are special settings needed in XCTU to send that RTK packet.
RicG:
The Xbee has many settings in XCTU that may require tweaking (such as receive and transmit buffers, or flow control threshold), but I have not been able to find out if this is required in this case?
I ran into what I think might be a similar issue some time ago. Using a [SparkFun XBee Serial Explorer, I noticed that RSSI light wouldn’t blink to acknowledge data received if it was powered on but not connected to a serial port. Further, even if it was plugged into the PC but the port temporarily disabled using my [serial test utility, it wouldn’t turn on.
My Xbee link problem was solved by simply connecting the Xbee’s directly to the F9P GPS module, instead of via the Xbee Explorer USB adaptor. I don’t understand this, but now my two F9P receivers now run in FIXED mode with a wireless connection.