Technical information

Cterm Serial Solutions

Menuout() deals with the function keys and the ALT-C

key. It reads the second byte of the extended key code and

interprets it as a request to perform a certain action, and calls

cmdout() for help, quit and commands, and setup() for the setup

option. Cmdout() decodes a character string as a command

(whether the string is from the keyboard, a file or a literal in the

program does not matter), calling one of the command execution

routines to do the actual work. Setup() present the user with a

group of menus to allow set up the serial port. It gets options

from the user and calls the command execution routines to

perform them.

Note the use of the function screen() throughout for output

to the screen. This function at this time simply calls printf(), but

is used so that future versions of CTERM can easily use

separate windows or a marking scheme to separate the three type

of text that appear on the screen- characters from the serial port

(’fromport’), echoed characters from the keyboard (’fromecho’),

and control information from the program (’fromctrl’). The

second parameter of screen() flags this. Figure 7-7 contains

examples of this.

Figure 7-7. Screen Output Examples.________________________________

if( echo & echos ) /* May need to echo character to screen. */

screen(c,fromecho);

inxlat(bf); /* Read in some characters. */

if(*bf != ’\0’ ) /* If some read in ok. */

screen(bf,fromport);

screen("Command not recognised\n",fromctrl);

The actual commands which access the serial port are

comparatively simple to use, and are almost hidden by the

remainder of Cterm. The user should not find any great

difficulty in using serial port from C.

Chapter 7 Page 127