ve3id wrote:Both lines work fine with both modems and the laptop.
The second line (which is giving the trouble) fails to receive anything more than RING and OK on an incoming call when I run standard terminal programs like minicom, screen, kermit, and also ser2net. I will test the first line with the pi tonight!
thanks for your consideration
Well it's a conundrum. Given the description of the situation I strongly suspect that it is *not* that the Pi is not *receiving* the caller-ID data, but rather that the modem is not *sending* caller-ID, although I don't know why. Either there's a hardware override, or the modem didn't actually receive the instruction to send caller-ID.
I suspect two things.
1) The serial port control lines
If you are using the Pi console port then there are no control lines (DTR, RTS etc.). How about making a wiring adapter for the laptop that connects only TxD, RxD and GND straight through, and try running the software on the laptop again.
2) Buffer overflow
Can you delay the commands sent by the Pi to configure the modem so that there is an inter-character delay, or a delay between AT strings? Is there a typo in the command string?
If you have a storage oscilloscope you could capture the bitstream sent by the laptop and compare it to the Pi (but not many people do).
How about using the laptop to configure the modem and then plugging the Pi into the modem? The laptop configures the modem and the configuration should persist.