I recently bought two RTK Express units and both of them failed within a week or two. They worked fine up until the display didn’t show anything when I tried to turn the unit on. There was some serial output on the ESP32 USB port when I powered it up but it only ran for a couple of seconds before disconnecting the USB and becoming unresponsive. They both had more than 50% battery charge when they failed.
Error: I2C Bus Not Responding Display not detected LittleFS Started SparkFun RTK Surveyor v3.2-Mar 8 2023 settingsFile not found in LittleFS settingsFile not found in LittleFS Error reading from serial device
Has anyone else had a similar problem, or have an idea what’s causing this?
Some additional info. I don’t if it’s relevant to the problem or not.
Latest ESP and UBLOX firmware installed In Rover mode and updating location every 3 seconds Data for PPP being written to a uSD card Unit failed while it was outdoors. Max air temp was in the low 90s Unit failed within 10 hours of being placed outdoors
When you say the units where outdoors for multiple hours, was there possibility of water ingress? The units are IP53 so there is some resistance, but certainly not weather proof.
That said, I suspect the accelerometer is causing the I2C bus to fail. Please consider sending the units back to us for repair: https://www.sparkfun.com/returns We can get most repairs done in ~24 hours.
Can you tell me more about why you think the accelerometer is causing I2C bus problems? I don’t think I need an accelerometer and, if it will bring a failing RTK Express back to life, I have the skills and tools needed to do surface mount work and could remove the accelerometer IC.
tldr; If you know what you’re doing, feel free to remove the accel using hot air.
The package is very small (2x2mm) and likes to trap flux under the IC. We use a no-clean process due to the ZED-F9x module but there is still residue. We suspect with humidity and exposure, over time, a chemical combination forms under the IC causing intermittent shorts between SCL/SDA and possibly 3.3V or GND to either I2C line.
Once SDA or SCL become inoperable, the display, GNSS, and fuel gauge can no longer communicate with the ESP32.
The accelerometer is only used for the digital bubble feature so we’re starting to remove the feature that has little value, but poses a potential unit failure.
The PCB is four layer with two internal ground layers so use high heat, with a short amount of time to avoid delamination.
Thanks for that info. I didn’t have any trouble removing the accelerometer chip. There was a lot of gunk on the nearby capacitors and some underneath the accelerometer chip. I cleaned it all up with 100% isopropyl alcohol and now the chip pads look clear of any shorts.
The result is that the display does come up now when I hold down the power button, but the unit powers back off right after the display shows which version of the ESP32 software is loaded (3.2). Here’s what comes out of the USB serial port in the brief time the unit stays up:
ZED-F9P firmware: HPG 1.32
LittleFS Started
SparkFun RTK Surveyor v3.2-Mar 8 2023
settingsFile not found in LittleFS
settingsFile not found in LittleFS
settingsFile not found in LittleFS
s
I don’t see any more I2C errors but the unit still isn’t working. Suggestions?
You’ve cleared the I2C bus error. The display is either broken, or there is a disconnect between the ESP32 and the display (bad cable or bad connector).
I presume you had to disable the unit to work on the accel. Be sure the Qwiic cable is connected. There are two Qwiic ports on the display board, try the other one.
If you exhaust those paths, you can either return the unit for a part swap or we can send you parts.