> From: John Samperi
>
> .... (USB Bootloader) ....
>
> I would suspect that would be rather large because of the USB
> firmware, but if you have the room why not.
>
> Most boot-loaders have been designed to squeeze into the least
> amount of flash. ....
>
> All of my boards just have a 4 or 6 pin header with the USART pin
> and power, I can then plug in anything, USB or RS323 or even ethernet
> dongles to communicate with the chip. No real estate taken.
Hi John,
I agree that your approach does, indeed, minimize board and code footprint.
The boards I am making are installed in the field and maintained by
inexperienced volunteers. I want to be able to email new firmware (fairly
frequent at the moment due to rolling out new features, etc.) to them and
make it as foolproof as possible for them to load it.
Since serial ports are scarce on modern laptops and I have had issues with
USB-Serial adapters in the past I was intrigued by the USB bootloader I
mentioned because my 'user' would not have to keep track of extra hardware,
just a USB cable which is more common than serial cables these days. The
only external hardware required by the bootloader appeared to be 5-6 passive
components (no level shifter required) and the code size of the minimal
configuration seemed fairly small.
In doing some more reading I discovered that one needs to check to see if
the USB bootloader needs a custom driver on the PC side - more complication
when dealing with volunteers.
Considering all this, I think I'll stick with a header and make an external
adapter for them to use. I guess if they could keep track of a USB cable,
they should be able to keep track of a USB-Serial adapter :-)
stevech11, DLC: Thanks for the pointers to the bootloaders, I'll check them
out.
Cheers,
Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck