Bob Blick wrote:
> But since you have not used a bootloader, you have not had the chance to
> see how useful it can be, even when one already has an ICD or ICE.

I have used everything you mentioned (ICE, ICD2, bootloader) plus direct
load via ICSP, and replace chip in socket that you didn't mention.

Of all these methods, the ICE is definitely the best for debugging.  You can
see everything going on in the chip in the real target circuit environment
without requiring additional resources, which can often be a serious
limitation.  The downside is that an ICE is relatively expensive for
hobbyists (it's a no-brainer for professionals where time=money and you get
the heft discount) and lately there have been more and more limitations as
the chips get faster.  Still, this is currently my debug method of choice
for most projects simply because it's the fastest way to get to working
code.

The ICD2 is a good value for the money, but I use it only grudgingly because
there seem to be some flakies and it has some annoying properties even when
it's working right.  Still, it's probably the best value for a serious
hobbyist.

Most modern PIC circuits are designed for ICSP.  For those it's easy to dump
a new version into the PIC and try it.  I usually set up a build script that
automatically dumps the HEX file to the PIC via a programmer if the build
succeeded.  As long as your circuit is set up for ICSP, this is better than
a bootloader in all cases since it requires no extra hardware resources, and
takes about the same time or less.  The only drawback from a hobbyist point
of view is that you need a programmer, preferably one capable of releasing
the programming lines to high impedence when done depending on how the
circuit is wired and the PGC/PGD pins used.  I think a minimum programmer is
a must for a hobbyist anyway, and that relying solely or mostly on a
bootloader is not a good idea.  I use a ProProg for this since the EasyProg
was not designed to release the lines when done.  The new USB programmer is
designed for that (working very nicely from a serial port by the way, faster
than the EasyProg and ProProg, USB software/firmware in progress).

I have used a bootloader a few times, generally when that was required for
the finished project anyway.  In that case it's about equivalent to an ICSP
dump since the hardware is designed for bootloader access.  In one case the
circuit wasn't designed for ICSP but the project required a bootloader for
field upgrades, so I used that.  However it's been a few years since the
last time I saw a circuit not designed for ICSP.  The drawbacks of a
bootloader are that there are too many things that can go wrong, it requires
hardware resources, and you still have to get the bootloader in the chip the
first time plus whenever you mess up and overwrite it.  Also many chips are
not capable of bootloading or a bootloader would take too large a fraction
of the limited program memory.  My 16F UART based bootloader is around 300
words if I remember right, and my dsPIC external IIC EEPROM bootloader is
about the same number of instructions.  Both were carefully designed for
reliability, so it should be possible to make smaller quick and dirty
bootloaders.  However, I think that is a bad idea since there are already
enough risks and hassles when using bootloaders.

In the end, I usually use a combination of initial test with the simulator,
then real debugging with the ICE, then testing incremental changes using
ICSP dump-and-run.  Once the firmware is basically working, bugs are minimal
and when they do occur you can usually find them from the symptom fairly
quickly.  At that stage I only haul out the ICE when I'm really stumped and
can't figure it out with a few minutes of testing.


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