I hope the UART-forum is the right one for my request. If not, please move it to the correct place.
According to the documentation (Telit_AT_Commands_Reference_Guide_r17.pdf), the module checks the DTR port-level if start mode 0 is selected. In our circuit-board, there is a 2.8V-LDO as VCCIO for an FTDI-USB-UART-Chip. The communication with the GC864-QUAD-V2 works fine. The 2.8V-LDO is only activated when a USB-cable is plugged in (USB 5V are the power supply for the chip). This is supposed to be used as a check whether or not the script shall be executed (if a USB-cable is plugged in, the terminal mode for programming is needed and thus, the script must not be executed). Conected to the DTR is also a pull-down resistor so in normal operating mode, the script is started.
The problem is, that no matter what the level on the DTR-pin, the script always starts. I have also used Pythons SER.getDTR()-function, but either way, with USB cable connected and disconnected, the return value is always 0.
All relevant connections are shown in the following image:
[Blocked Image: http://i.imgur.com/G7AVq1a.png]
If there is anything left unclear, feel free to ask and I will answer. Hopefully, someone can help me with this issue.