After getting ssh access to the dongle, I was able to install and configure gammu-smsd. After checking the serial ports I found:
/dev/ttyAMA0: ELM327, the OBD Adapter
/dev/ttyUSB0: From messages log: “usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0”
/dev/ttyUSB1: No answer to AT command. What is it used for?
/dev/ttyUSB2: AT commands checking for GPS (“AT+QGPSLOC=2” “+CME ERROR: Notfixed now”)
/dev/ttyUSB3: Answers to AT commands. So possibly usable for gammu-smsd
So configured gammu-smsd to use ttyUSB3. Started and received some SMS. So I thought everything is fine.
The bad awakening comes after a reboot. No AP anymore, no cloud connection. So the only posibility I figured out, was to open the housing and connecting a monitor and a keybord, Then I realised that the PI hungs up completely with salt hanging at 100% CPU, 10s after booting has finished. So needed to mount the SD card externally to disable gammu-smsd.
So my conclusion for now:
- /dev/ttyUSB3 is used by salt stack. It is not really a bug, but there should be a timeout and error checking on all serial communication, and even a log, There could even be a hardware fault which can’t be found in any log actually, when PI hungs up.
- The PI’s onboard serial ttyAMA0 can’t not be used as serial console, because it is connected to OBD adapter.
- gammu-smsd can’t be used, because it needs a serail port with at commands.
- Handling incomming SMS needs to be implemented in salt stack and made visible in cloud.