As of build 946.6 of 26 Novenber 2005, A-Shell/ATE supports ZTERM-type serial passthrough.

Enable passthrough:

? chr(27); chr(27); chr(3); params$; chr(0);

Disable passthrough:

? chr(27); chr(27); chr(4);

params$ is of the form:

"<port#>,<baud>,<parity>,<databits>,<stopbits>"

For example:

"1,9600,E,7,2" (COM1, 9600 baud, even parity, 7 bits, 2 stopbits)

When enabled, input from the serial port is merged into the keyboard channel input. Output characters are not normally sent to the serial port. To enable that, send ^X (ASCII 24); send ^T (ASCII 20) to disable. Note that these are the standard AUX PORT ON/OFF commands for the AM6x emulation, but when they are sent while serial passthru is enabled, they have the effect of sending the output to the defined serial port rather than to the printer port.