I couldn’t find any clear reference design for using the UART to connect to a microcontroller, does one exist, I’m not quite sure what to make of the DTR? The mangOH does have a schematic but the DTR signal tracks to a header with no information how it’s meant to be used.
HL7692 spec has this to say about the DTR signal:
Prevents the AirPrime HL7692 from entering sleep mode,
switches between data mode and command mode, and
wakes the module up.
Checking some other threads, it appears that this is the (only) way to wake up the module if it’s in sleep mode, fair enough.
However the AT command interface guide says this:
DTR/AT&D is only applicable to the USB AT port; it has no effect on UART1
Wut? So when I’m not using USB, DTR is strictly used to keep the module awake with no other function?