Hi
I am having an issue with the SARA R4 board I bought a couple of months ago. Today I connected a lipo cell to it and it worked fine for a while. I beleive that I also hot-plugged the sim card once in the process.
Now I have a major issue.
I have a FTDI serial adapter connected to the board so that I can write AT commands to the modem. The problem that have arrisen now is that AT commands only work for around 5 seconds after startup, then it seem like something gets connected to my computer over the USB on the SARA R4…
To be exact the device that appears in device manager is named “Qualcomm HS-USB MDM Diagnostics 90B2”. Only one device appears and “Qualcomm HS-USB Modem 90B2” does NOT appear in the list. (just to be clear, I am not trying to use USB at all, this is just the properties of the issue)
I also recently found out that if I unplug the SIM-card I can actually access the AT interface over the FTDI uart adapter I connected to it and now it does not time out. Also when there is no SIM-card inserted it does not add any interface on the connected windows-computer.
What could have happened? I know there is a VUSB_DET jumper on the back side, but this jumper is open and I have not done any changes. Could this be a known bug or something?
Kind regards
Jens
Hi Jens.
This isn’t a bug as far as I can tell. We’ve not had anyone report this before.
I suspect the module on the board is establishing a connection via USB to your computer and that’s disabling the UART on the module. I’m assuming you’re using the USB connector for power, have you tried connecting the USB connector to a phone charger rather than a computer to see if that keeps the UART active?
One other thing to try is to make sure the module is powered on and then press and hold the reset button on the shield for at least 10 seconds. That should restore the modules factory defaults in case a setting somewhere is causing trouble.
You are correct I am using USB for power only. It was connected to my computer.
Now I switched to a red “charge only” port on my USB hub and it gives the same results. After a couple of seconds the boards stops echoing or replying to commands.
And even though it tries to switch to usb communication, wouldnt that be impossible since the VUSB_DET jumper on the back side is open and not closed?
I have also tried to reset it by holding reset for 10 seconds.
Also as I wrote, I can write commands forever, unless I put a working SIM card in, then the behaviour returns. So
Sim card inserted - just 5 seconds of commands
Sim card ejected - can write AT commants forever.
Isnt this strange?
Some more info
If I actually connect the USB to a real USB on my mac, at the same time I lose connectivity with the serial port the device shows up like this when I run lsusb
$ lsusb
…
Bus 020 Device 011: ID 05c6:90b2 Qualcomm, Inc QHSUSB__BULK Serial: fba2f9a1
…
Googling for QHSUSB__BULK I see a lot of pages regarding bricked Android devices with Qualcomm chipsets. This makes me think that the SARA R4 might be broken and end up in some kind of recovery mode.
Anyone seen anything like this?
Have anyone seen anything like this? Is my board broken?
Hello Jens.
I’ve been able to replicate your issue here and it seems that you can’t have UART and USB active at the same time. The SARA module monitors the USB connector for power and if it sees power there, it disables the UART interface. Try powering the module with 5 volts DC at the 5V and GND pins and see if that clears things up for you.
One other thing. Did you purchase the shield directly from SparkFun and are you in the United States?