Re: Adding USB Interface to Low-Cost 8-Bit Microcontroller

On 2008-06-10, David T. Ashley <dta@xxxxxxxx> wrote:

However, what is required to implement a USB interface in the product (for
an 8-bit microcontroller), and what is required as far as a driver on the PC
side? The goal would be that we distribute a re-FLASHing application to the
customer that runs on the PC. They would run this application with a USB
cable connected from the PC to our product.

Others have already directly answered your question so I'm not
going to. However, are you sure that you really need USB? You
seem to have gone from requirements to that conclusion in a single
bound so I can't help suspecting maybe there is a little tunnel
vision here.

Many flash memory card formats have integral SPI interfaces - Secure
Digital comes to mind. Since you already have an SPI interface
you can add SD support to the hardware with little more than adding
a connector assembly and making whatever modifications are necessary
to the PCB and case. USB card readers are cheap - SD readers are
under a fiver retail here in the UK, and that cost and the cost of
the card itself are only necessary if the customer wishes to upgrade
- I suspect that will be a minority for most consumer devices.

Of course, you will need software on your device to read the card
and reprogram the device accordingly, but you will need some software
however you go, and that software will almost certainly be simpler
than adding USB support. The software will be greatly simplified
if you can dump your new flash image to the card as a raw device,
rather than needing to deal with a filesystem layer.

--
Andrew Smallshaw
andrews@xxxxxxxxxxxxxxxx
.

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