Re: Upload Options

Tom Lucas wrote:

I'm designing a system based around a Sharp 79524 ARM7 part which will be
required to be occasionally reprogrammed in the field with around 16MB of
data from a PC.

Serial - Too slow but nice and simple. Perhaps I've missed a revolution and
PCs can now handle super high rates but I suspect that 115K is the limit for
most.

Should take 20 minutes. That's not too slow for an occasional upgrade
*if* the host application displays a believeable progress indicator,
such as counting minutes until done. It is too long to sit at a simple
'please wait' screeen with no indication that it's not dead.

USB - The Sharp has a client controller built in which helps but I've heard
that getting it all working is a nightmare. Commercial stacks seem to be
pretty expensive too. Good for plug and play.

That probably is the best option of it's done frequently. Also with
serial you may need to supply some customers with a USB-to-serial
dongle anyway. Another option is to build one like the CP2102 ($5 from
digikey) into your product - though that may not go all that much
faster than a serial port. Or they may - hyperterminal just let me
open a belkin usb-to-serial dongle (different chip) at 921600 baud,
though if it actually works there is a mystery.

Compact Flash/SD card - Simple to program and cheap but requires taking the
back off the system to insert the card

Put the card slot on the front panel then. Customer shouldn't program
the card, you should and mail it to them. Don't use a filesystem, or
at least don't use a standard one (use something very simple just
capable of steering you around bad blocks). Program the card in a
linux box and mail it, customer inserts it. No worry with customer pc
configuration at all.

JTAG - Perhaps with customized probe? Fairly quick and not too tricky for a
user to use (pig of an application to write though!) but does give them
rather too much access to the inner workings of the system.

No way is JTAG faster than serial unless you have a specialized pod
driven by USB or something ($100+) the classic cheap parallel port
cable is bit-bang serial, wheras an ordinary serial port has hardware
shift registers and hardware buffering. Note you don't have to give
them jtag access to the processor, you could give them a jtag chain
containing only a serial flash chip where your code resides.

.

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