gnupic: Re: [gnupic] [ANN] Pikme PIC Bootloader (for 16F819 etc)
Subject:
Re: [gnupic] [ANN] Pikme PIC Bootloader (for 16F819 etc)
From:
"Frank Sergeant" ####@####.####
Date:
25 Jul 2006 22:19:26 +0100
Message-Id: <11091.1153862377@bed.utoh.org>
Tamas Rudnai ####@####.#### wrote:
> I am still wondering what are the advantage of a bootloader /
> bootstrap? Is is because you would like to make it possible to update
> the firmware by the user / engeneer?
I had been pleased with the JDM-style serial PIC hardware programmers
(the PG1 and PG2 made by Olimex and also sold by Spark Fun). They are
*very* reasonably priced and had been working fine for me (via pikdev on
Linux).
Recently, I couldn't get some 16F819 chips to program and verify
reliably. No, I did not change my desktop PC or its serial port. I
tried 3 or 4 PCs. I measured the Vpp (only statically, so it still
might have been marginal). Did I get a "bad" batch of '819 chips that
might have needed e.g. 13.5 V rather than only e.g. 11 V?
Besides, the JDM approach does not use the PC's serial port ground as
the circuit ground, which meant, even when I was using chips that PG1 or
PG2 could program ok, that I often needed to unplug the programmer from
my development circuit before I could test it, and then unplug whatever
from the development circuit before I could re-attach the programmer. I
hate the plugging and unplugging (and sometimes forgetting).
So, I bought the Olimex PG3 parallel PIC hardware programmer from Spark
Fun. (I should have bought their parallel cable at the same time, as a
number of my parallel cables did not work -- fortunately one I had did
work). Here, ground is ground, and I've been very happy with it.
However, there can still be a lot of plugging and unplugging, if your
project's circuit's use of pins conflicts with the hardware programmer's
pins.
So, to summarize: fast turn around while developing. I like a
bootloader to eliminate the plugging and unplugging. There are other
ways to eliminate the plugging and unplugging, but I think a bootloader
is the simplest. My bootloader takes just one pin on the PIC -- a pin
that my circuit does not need for any other purpose. I can leave it
connected the PC's serial port all the time.
I have mixed feelings about a (remote) user/customer upgrading the
firmware. Yes, a bootloader can be used for this. I have indeed used
it for this. I guess it depends on the circumstances.
I might like the idea of a bootloader for burning the application at
production time, but I worry too much about whether the bootloader
itself would get burned correctly into the chip before it is soldered
onto the PCB. If it didn't, then what do you do? I think you have to
be sure you can attach a hardware programmer. I like Spark Fun's
approach of not soldering a programming connector, but just leaving the
holes in the PCB. Then the connectory is held in place manually when
programming. If you use a DIP, you could use a DIP-clip (if nothing else
on the PCB prevents the clipping part). You could use a bed-of-nails
approach. You could just throw the bad board away. In other words, I
am nervous about relying totally on a bootloader for production
programming of the application.
Just some quick thoughts.
--
Frank
