Make file with objects in one directory

Hi,
I am new to unix make and so, this question may sound little silly. But
please help.

I need to compile a list of .c and .cpp source files that are in a big
directory structure.

Ex:

/code_root
 /design/tools/test1.c
 /design/tools/test2.c
 /design/src/tcpstack.cpp
 /design/src/tcpsrlze.c
 /design/src/util/charconv.cpp
 /arch/src/frmwrk/frmroot.cpp

like wise there are about 700 files in the directory structure.

I need to write a unix make file that can compile all these files and
then create the objects in one directory namely
/code_root/obj

Can some please help on how to write?

I have the following, but it compiles into the source itself.

$OBJECTS= \
/code_root/design/tools/test1.o \
/code_root/design/tools/test2.o \
/code_root/design/src/tcpstack.opp \
/code_root/design/src/tcpsrlze.o \
/code_root/design/src/util/charconv.opp \
/code_root/arch/src/frmwrk/frmroot.opp \

all: $(OBJECTS)

%.o:%.c
   $(CC) -c $< -o $@

%.opp:%.cpp
   $(CC) -c $< -o $@

Well, I downloaded this code from some where and I kind of understood
what it is doing. But couldn't change it to get what I want.

Thanks in advance for your help.