I am attempting to connect a TI-89 graphing calculator as a serial terminal to a Raspberry Pi running the latest version of Raspbian. The calculator is emulating a PL2303 serial adapter at /dev/ttyUSB0 and is able to send and receive text from minicom running on the Pi. However, when trying to start a command-line on the device there is no prompt to login. The Pi is using systemd and when I run
systemctl start serial-getty@ttyUSB0.service it executes without error.
systemctl status serial-getty@ttyUSB0.service returns the following:
● serial-getty@ttyUSB0.service - Serial Getty on ttyUSB0 Loaded: loaded (/lib/systemd/system/serial-getty@.service; disabled) Active: active (running) since Mon 2016-04-25 01:30:27 UTC; 9s ago Docs: man:agetty(8) man:systemd-getty-generator(8) http://0pointer.de/blog/projects/serial-console.html Main PID: 6523 (agetty) CGroup: /system.slice/system-serial\x2dgetty.slice/serial- getty@ttyUSB0.service └─6523 /sbin/agetty --keep-baud 115200 38400 9600 ttyUSB0 vt102 Apr 25 01:30:27 calcpi systemd: Started Serial Getty on ttyUSB0.
The calculator at this point receives two carriage returns and nothing more. Tying to send any commands from the calculator to the Pi has no response, including the ASCII control codes: ACK, SYN, DC1, and ENQ. I have been looking for information in regards to the protocol used here in case there is supposed to be a response on the calculator side before the login prompt with no luck. Any suggestions on how to get a login prompt to appear would be greatly appreciated.
Update: When trying to start the command-line using just agetty rather than systemd I was able to pass an initial string as an argument and the first character of the string is displayed on the calculator. So for example
sudo agetty -I "Hello world" -L 9600 ttyUSB0 vt100 displays H on the calculator.