BSP Developer's Guide

3
Creating a New BSP
might want to add additional hardware initialization code that is called before the
kernel is started. In this case, you can add a hook right before the call to
kernelInit( ). As an alternative to hooks, you can call routines from the debugger
by using the GDB’s call procedure. For example:
(gdb) call myHwInit2
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The advantage of using hooks instead of the call mechanism is that:
■
Hooks let you avoid executing the original code.
■
Hooks are much faster.
If your board has an “abort” button, consider connecting a debug routine to the
abort interrupt. Then you can set a breakpoint on your interrupt handler from the
debugger. This provides a way for you to gain control of the system if it appears to
have died. In this case it is best to have the abort switch tied to a non-maskable
interrupt (NMI).
! WARNING: Only fatal interrupts such as “abort” can be connected to an NMI. If a
device interrupt is connected to an NMI, the kernel will not work properly.
3.4 Using a Minimal Kernel
A minimal kernel involves adding just a few simple device drivers. Because these
drivers involve connecting interrupt service routines, this section starts with some
ISR guidelines.
3.4.1 ISR Guidelines
After the kernel is started, you can use the intConnect( ) routine and
INUM_TO_IVEC macro to connect interrupt service routines (ISRs) to the interrupt
vector table. For example:
intConnect (INUM_TO_IVEC (intVec), proc, param);
The intVec parameter is the interrupt vector, proc is the C routine to call in response
to the interrupt, and param is a parameter to pass the proc routine. For more
information, see the reference entry for intConnect( ).
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