On Mon, 26 Apr 2010 13:29:56 -0700, Vitaliy wrote:
> Matt, thank you very much for sharing this information. We'll definitely
> take another look.
>
> So can you say whether the UART interface is (or can be made to be)
> "transparent"? In other words, can it work as a serial cable replacement
> "out of the box", without the need to send it configuration commands from
> the micro?

I took a quick look through the Programmer's Reference as well as looked
through the drivers to see if there was any hint of using the UART function
for the Host interface.

I didn't find any functions for changing the Host interface from SPI to
UART at all. The only reference to the UART was for status messages from
the module's CPU so I am assuming that the firmware in the module CPU
limits it to this function, possibly some debug commands too. There is
nothing in the hardware design guide that hints you could change the
function by strapping a pin to a certain logic level either.

I will say that using the UART as the Host interface is likely to be a bit
slow in terms of data throughput. Most of the Host writes to the module
registers require transferring numerous bytes. A quick look at a few
commands in the driver look like ~9-11 byte transfers, not counting data
bytes. I know in our product we are using a 20 MHz SPI interface and we
don't have to wait on the module.

You have me curious now though. I may have to start prodding my Microchip
contacts to see what the status of these modules is and if any new
information is available.

FWIW, we have had very little trouble with them, they seem to just work.
There was one small issue connecting with some Linksys routers but ZeroG
had a workaround that fixed it. They may have updated their firmware by now
to correct it (it was actually a bug with the Linksys router).

Matt Pobursky
Maximum Performance Systems


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