[syslinux] syslinux vs isolinux - com32 serial port output problem

[Janz, Burt]

I have a need to display text to COM2 before loading a kernel.  The easiest way to do this was to invade menu.c32 (menumain.c) and add a function to send the string out to the serial port just before the selected menu "label" is executed. In menumain.c, my function is called just before 'if (cmdline)'.


The code I wrote to initialize the hardware and send individual characters to COM2 works as expected when I boot from a USB drive (syslinux): the text is seen on COM2.  However, when I boot from the CD, I don't see any output on COM2.?


syslinux.cfg and isolinux.cfg are identical.  menu.c32 executes properly on the CD, so I'm assuming that I have all the needed com module support on the CD.


In both cases, the system boots up as expected.  The only difference appears to be the missing output on COM2 when booting from a CD.  Yes, I have tried this using different CD drives.  I have even tried this on a couple of different systems (a "final ship" and an open-frame "test fixture").


Any ideas?


--
Burt Janz
Principal Embedded Engineer
Exelis / Harris
85 Northwest Blvd.
Nashua, NH  03063
603-459-2255

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