Board: SparkFun Triband GNSS RTK Breakout - mosaic-X5
Purchased: August 28, 2026 (board has only been in use for a few days)
Issue:
The USB connection to the module resets/reconnects constantly and continuously — this happens regardless of state. It is not that clicking a button triggers a reboot; the connection itself is unstable and keeps dropping and re-establishing on its own.
Because of this, I only get short windows where the connection is stable enough to see anything:
Most of the time, when I do get a stable-enough window, the web interface at 192.168.3.1 shows the “Upload a SUF File” page with a “Reset to normal firmware” button — meaning the module is in the Ready-for-SUF / protective mode.
On one occasion, I was able to briefly reach what looked like the normal firmware interface (not the SUF upload page) — but even then, the USB connection kept resetting constantly, so I could not do anything useful before it dropped again.
Because the connection never stays up long enough, I have not been able to complete a .suf upload via the web interface, nor via RxTools RxUpgrade over the USB virtual COM ports (USB1/USB2) — the COM port itself keeps disconnecting/re-enumerating mid-transfer.
Troubleshooting already done:
Antenna disconnected before attempting the reset (per the documented 4x-reset trick)
Different USB cables tried, direct connection to PC (no hub)
Tried both the web interface (192.168.3.1) and RxTools RxUpgrade over USB1/USB2 — same constant disconnect/reconnect behavior in both cases
Firmware file on hand: mosaic-X5-4.14.10.1-failsafe.suf (from the SparkFun_RTK_Everywhere_Firmware_Binaries repo)
Question:
Given that this is a brand-new board (purchased just days ago) and the USB connection itself is unstable independent of which mode the receiver is in (normal firmware vs. SUF recovery), does this point to a hardware defect on the module rather than something a firmware/SUF upload could fix? Happy to provide a diagnostic report or SBF support log if that would help.
I can only think of two things that would cause the disconnections:
An intermittent joint on the USB-C data lines
Or, your computer cannot deliver the 300mA-400mA the X5 needs. It needs more than that if you have a microSD card inserted.
Please have a good look at the soldering around the USB-C connector pins. Does anything look suspicious? If you lift the USB cable connector gently “up”, does the connectivity improve? Please post a close-up photo here so we can take a look.
If you have one, please try powering the board from a 5V >1A USB wall adapter. With the antenna connected, after 30-60 seconds, does the PVT LED light up and stay lit? If it does, please try the same test when connected to your computer. Ignore the web page connectivity. Does the PVT LED light and stay lit?
I connected the Module via a externally powered I-tec USB Hub that ist able to deliver higher currents. Then I also tried various other Hubs and direkt connection to my laptop. All the time the same sympthom of a reebooting mosaic-x5.
than I provided 5V via an external laboratory Power supply on VUSB and VIN. Without a connected USB and without SD CArd inserted i can watch the power consumption and on 5V the module starts to draw around 120-140mA and LEDs PWR, PPS on. Than after maybe 20 seconds, LOG, PVT, RTK LED blink shortly and the power consumption pikes to around 200mA just to drop again to 120mA for another 20 sec and that repeats forever
Than I Provided 3.3V via an external laboratory Power supply on 3.3V Pin because I thought maybe the AP2112 is damaged, but the reboot cycle repeats the same
USB Conenctor and Virtual Com port get disconnected constantly
Now I connected a FTDI Serial to USB Transceiver to the boards COM1 while providing 5V via an external power supply.
The Serial ouput now was periodically:
COM1>$TE Septentrio receiver is booting.<\r><\n>
COM1>$TE Septentrio receiver is booting.<\r><\n>
COM1>$TE Septentrio receiver is booting.<\r><\n>
But in short window I was able to stabilize that reboot scenario by sending command :
login, admin, admin
followed by :
factoryReset
gave the result:
COM1>$TE Septentrio receiver is booting.<\r>
<\n>COM1 ssn-linux GRB00** SN 442****: Ready for SUF download …<\n>COM1 ssn-linux GRB0051 SN 4422207: Ready for SUF download …<\n>COM1 ssn-linux GRB00** SN 442****: Ready for SUF download.
Now I was able to Connect the “RxDownload” tool via the FTDI bridge and flash a new/old Firmware “mosaic-X5-4.14.10.1.suf”
But with FW “mosaic-X5-4.14.10.1.suf” the same periodic restart happens. USB Driver keeps disconnecting.
Then I was able to install “mosaic-X5_fwp_4.15.1” via the FTDI bride but same result. USB Ports keeps periodically disconnecting.
After that I installed “mosaic-X5_fwp_4.15.0” via the FTDI bride but same result. USB Ports keeps periodically disconnecting.
Since the module is only 7 days old and obviously damaged. I want to send it back to Sparkfun and get an exchange module.
attached is the picture. But honestly i dont think the error is related to bad USB soldering becaus i can see the reboot cycles by watching the current draw and LEDs periodically cycle.
For me it looks like the Mosaic-X5 boots up while drawing 120mA and then after its booted around 200mA for a few seconds its restarting. Somehow it wont stay in its main software.
That behavious is the same with or wishout connected USB. USB reconnecting is just the symptom not the reason for that behaviour. Somehow the Mosaic doesnt stabilice in its main firmware. Bootloader works, because i can flash new firmware, but starting the firmware regardless of iots version starts the periodically power cycles.
Please proceed with the return. It is clear you need a new board.
Just for interest, please give the RST button a few presses. Does it feel normal? Is there a positive click when you press the button? (I am wondering if the button is faulty and possibly causing random resets? But it seems unlikely that the firmware upgrade would succeed if the button is generating resets.)
