■ BY PETER BEST
FLIGHT TESTING THE ARM
WE GOT OUR ARM PROJECT TO “HOVER” LAST MONTH. This go-round, we’re
going to do a bit more flight testing. Right now, our ARM system consists of
the bare essentials. For starters, we will add another serial port in addition
to the existing serial port that is doing double-duty as the ICSP portal. We’ll
also design in a 20-pin JTAG interface that will allow us to go beyond
the capabilities offered up by the free LPC2000 Flash Utility. I’ve noted the
additions in the updated LPC2136 schematic (see Schematic 1).
If you’ve been around microcontrollers, it doesn’t take very long to
realize that the really important part
of any microcontroller tool chain is
the debugger. A good compiler makes
life a bit easier on the coding side, but
a good debugging system provides a
bird’s eye view of the microcontroller’s CPU and internal peripherals.
The big advantage of owning a good
ARM debugging system is that if
you’re new to the ARM microcontroller and its associated compiler,
you can use the debugger to halt exe-
cution of example code and study its
operation and note what effects the
code is having on the ARM hardware.
As I alluded to earlier, a high
quality C compiler will help you avoid
some of the traps laid by lower quality C compilers that contain bugs and
“gotchas” that can ruin your programming day. You get what you pay for
and a higher quality compiler will
most likely have fewer bugs and
“gotchas” associated with it. And,
you’re probably going to get a better
technical support structure with a
quality C compiler you purchase from
a proven C compiler vendor.
Debugging is fun (at least to me it is),
but all good things must come to an
end. Once you’re happy with your
ARM code, you’ve got to put it into
ARM Flash before it can be useful.
Thus, a suitable ARM programming
mechanism is also essential.
It is important to consider flexibility when collecting parts and
pieces for your ARM tool chain. Do
the ARM debugging and compilation
components you’ve chosen allow you
to move to other similar microcon-
■ PHOTO 1. This unassuming little box
holds the key to the magic of debugging
and programming our LPC2136 using
a JTAG interface. This is a must-have
device as it can interface to an ARM
target using free and more feature-rich
licensed debugging tools.
troller platforms from differing manufacturers? Unless you work for Royal
Philips, every ARM project you
produce most likely won’t include a
Philips ARM microcontroller. Buying
C compilers and debugging hardware
for various types of ARM microcontrollers can get expensive. If you feel
that you’re going to do more than one
ARM project, invest in quality tools.
You’ll find that you pay a bit more for
a C compiler and debugger that can
handle the whole ARM7 family.
However, you’ll also come to realize
that it will cost you more to buy
multiple cheaper C compilers and
I test drove a number of ARM C
compilers and debuggers. One of the
better sets of JTAG-based debuggers
and supporting debugging software I
came across is manufactured and produced by Segger. Segger also offers an
ARM Flash programming system and
the Segger programming/debugging
software runs seamlessly with the ARM
C compiler from IAR. I’m really anxious
to show you the cool ARM stuff I’ve discovered. So, let’s take a look at my collection of Segger/IAR ARM tools.
J-LINK FOR ARM
Although my J-Link sports an IAR