On Mon, Jun 27, 2011 at 12:42:16PM -0400, PICdude wrote:
> I've looked into bootloaders in the past primarily to be able to =20
> program with less pins.  However, the usual TX/RX pins are in use for =20
> something else in my app, so they haven't been a good option.  =20
> One-wire would be really nice for this, but the PIC would have to be =20
> the master, and the code storage device (since I don't want to call it =20
> a programmer here) would have to be the slave. Anyone ever seen one of =20
> these?

That's an interesting idea. Seems to me that the CSD would still need to be
an active component acting as a server and a protocol converter. At first
glance the right part for the job sould be something like a PIC 12F1822.
It's 8 pins, has a full MSSP so it can do I2C and SPI along with a full
hardware EUSART. And it can be configured so that both pieces of hardware
can run at the same time. So something like this:

1. 12F1822 with half duplex one pin serial interface to the target.
Could be a simple as a wire OR config using diodes along with a pullup akin
to the I2C interface.

2. sdcard interface connected to MSSP running in SPI mode.

The target initiates by syncing with the CSD to establish the data
transmission rate and existance of the CSD. The CSD responds with available
load options (or none of no card is plugged in.). The target chooses the
firmware to be loaded which the CSD provides.

Just a quick thought on the process.

BAJ


>=20
> Cheers,
> -Neil.
>=20
>=20
> Quoting Michael Rigby-Jones <Michael.Rigby-Jones@oclaro.com>:
>=20
> > There is no "bootloader" mode required by a programmere, you simply nee=
d
> > a standard programmer (e.g. ICD, Pickit etc) in order to burn the
> > bootloader code to the micro, and then you need some method of sending
> > data to your bootloader (often some kind of serial protocol over RS232,
> > but could be I2C, CAN etc. depending on your application.)
> >
> > Mike
>=20
>=20
>=20
>=20
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--=20
Byron A. Jeff
Department Chair: IT/CS/CNET
College of Information and Mathematical Sciences
Clayton State University
http://cims.clayton.edu/bjeff
--=20
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