gnupic: Re: [gnupic] About a USB programmer I found
Subject:
Re: [gnupic] About a USB programmer I found
From:
Byron A Jeff ####@####.####
Date:
19 Aug 2006 15:19:33 +0100
Message-Id: <20060819141336.GA13878@cleon.cc.gatech.edu>
On Sat, Aug 19, 2006 at 09:58:45AM +0100, ####@####.#### wrote:
> Mornings guys,
>
> I found this programmer:
>
> http://www.create.ucsb.edu/~dano/CUI/#Sec2
It's not a programmer. It's a bootloader. To quote the page at the end of
section 1.0:
"Program the PIC18F4550 by downloading the .hex file via bootloader using the
PDFSUSB.EXE program."
I'm a bootloader fan. So it's probably a cool idea. Thanks for pointing out
the page to me.
> And I have received a 18f4550 from microchip, and got almost all the components needed.
Using USB there isn't too very much there.
> I just wondered, if someone could confirm me that once I build the circuit,
> I'd be able to upload the boot file to it (if it's the first thing I should
> do, still don't know), so I could start programming and testing with it?
No. The page was also clear about that. In section 4.4:
"The easiest way to download your bootloader into the PIC is through the ICD2
programmer menus in MPLAB."
Of course the authors simply glossed over the classic chicken and egg bootloader
problem. The bootloader eliminates the need for a programmer in most circumstances.
However to get started, you still need a programmer.
> The thing is that I haven't got a programmer, and instead of buying one (no
> one is selling programmers where I live so I must buy it through internet),
> I've been quite a while googling for one that would be self-programmable so
> to speak, so I don't need external programmers or other things.
It doesn't exactly work like that. You at least need to put together some
simple programming hardware to load the bootloader. This is one of the main
purposes of my Trivial PIC programmer project, found here:
http://www.finitesite.com/d3jsys
The goal is to generate a rather cheap, generally reliable, simple to build
programmer to dump the bootloader into the PIC. The Trivial programmer is
simple enough so that you can build one on a breadboard in less than a 1/2
hour, use it to dump your bootloader, and then disassemble until the next time
that you need it.
I have some additional notes sice I haven't update my web pages for a while:
1) The 18F4550 requires a Vihh (programming voltage) of Vdd + 4.0V. So if you
use my Trivial High Voltage Programmer (http://www.finitesite.com/d3jsys/proghvp.html)
then instead of 13V you can use anywhere between 9V and 12V. The easiest voltage
source probably would be a 15-16V wall wart and a LM7812 voltage regulator.
2) That schematic doesn't have any cable termination. One of my users discovered
that grounding the shield through a small valued capacitor on the target side
allows for long cables (longer than 2ft) to work.
3) WinPicProg by Nigel Goodwin (http://www.winpicprog.co.uk) has several good reports
working with the Trivial Programmers. Check the forums for configurations.
4) If you don't have an HCT part such as the 74HCT573, you can use a 74LS part
with a pullup resistor in its place.
The Trivial Programmer is a junkbox programmer. You build it out of the components
in your junkbox, program your part, then throw the parts back into the junkbox.
If you have any other questions, you can direct them to my forum. It'll E-mail
me when new posts show up, so I usually reply within a day or so.
>
> If not, if someone knows about some other circuit I could build with an
> 18f4550 it would be great. I'm trying to get advantage on USB since I use a
> laptop, which hasn't got any serial or parallel port. I use linux as well.
You then have another problem. The bootloader software that comes with the board
that you were planning to build is Windows based. There are no guarantees that
it'll run under Wine.
And you're where I argued that most PC users will be in a short amount of time.
With no other ports than USB, you'll have to purchase a programmer in order to
program the bootloader. You'd almost be better off spending the $50 and buying
the premade board.
You only other option is to get someone to dump the bootloader into a 18F4550
and send it to you.
Can you get temporary access to another machine with a parallel port? The good
thing about using a bootloader is that programming it is a one time operation.
So you don't need to keep a machine with another type of port, just use one
long enough to get the bootloader into the PIC.
And you must still resolve the software issue. You asked about another path
and I think one exists. Take a look at this page here:
http://pic18fusb.online.fr/wiki/wikka.php?wakka=UsbBootload
It's a detailed tutorial on building a PICDEM clone with Microchip's USB bootloader.
Now there's Linux software to use this bootloader. You can find it here:
http://www.internetking.org/fsusb
Of course you're still stuck in the chicken/egg loop of getting the bootloader
onto the part. My THVP programmer with WinPicProg will do the job, but you need
a parallel port to pull it off.
I hope these resources help you. I'm glad you asked the question as it gave me
a chance to do some USB bootloader research on a Linux platform. In fact I
think I have a 18F4550 floating around here somewhere... Hmmm.
BAJ
