RE: Eagle 100 (Stellaris LM3S6918)

["Christophe Coutand" <ccoutand@stmi.com>]

Hi Frank,

> -----Original Message-----
> From: Frank Pagliughi [mailto:fpagliughi@mindspring.com]
> Sent: 23. juni 2011 18:48
> To: John Dallaway
> Cc: Christophe Coutand; eCos Development List
> Subject: Re: Eagle 100 (Stellaris LM3S6918)
> 
> On 06/23/2011 10:30 AM, John Dallaway wrote:
> > Hi Christophe and Frank
> >
> > Christophe Coutand wrote:
> >
> >> I had the same thinking as Frank when adding the lm3s family, i.e.
> create
> >> a new package every time a new LM3S series is added, in the present
> case,
> >> a new lm3s6xxx layer that covers all 19 devices.
> >>
> >> The interrupt mapping in lm3s/var/include/var_intr.h should cover
> all series
> >> as far as I could see. Few interrupts are currently missing, they
> shall be
> >> filled as new series are added. The lm3s/var/include/var_io.h can be
> extended
> >> to include Ethernet, CAN, USB register definitions etc.. I use the
> >> lm3s8xx/include/plf_io.h to refine the set of peripherals included
> in each
> >> device of the 800 series. Since sub-series of the 6000 series have
> different
> >> memory sizes, the memory layout must be included in the board
> specific package.
> >>
> >> In addition, current device drivers for the LM3S (I2C, ADC) are only
> >> constrained to use the LM3S HAL and not constrained by series or
> sub-series.
> >> In practice, this means that using the LM3S ADC driver with the
> LM3S800 for
> >> instance, will not raise any dependency error during configuration.
> Since the
> >> LM3S800 does not have an ADC peripheral, the
> lm3s8xx/include/plf_io.h will not
> >> allow the lm3s/var/include/var_io.h to define the ADC registers,
> therefore,
> >> the ADC driver will not compile. I believed this to be ok, users
> most have a
> >> minimal knowledge of the hardware in use.
> > As long as the refining of definitions performed in the "LM3S series"
> > HAL packages such as lm3s8xx provide information that is truly
> specific
> > to that series and cannot be inferred simply by testing for the
> presence
> > of various peripheral driver packages, then I don't see any problem
> here
> > and it would make sense for Frank to follow this pattern by creating
> an
> > lm3s6xxx HAL package.
> 
> That makes some sense. But two things:
> 
> (1) I worry a little about the implementation of a lot of code that I
> wouldn't be able to test - like creating the plf_io.h definitions for
> all 19 chips in the lm3s6xxx without the ability to test any but one.
> But I suppose that would shake out in the long run.

The same dilemma applies to the lm3s8xx package that covers 9 chips. It's not possible to guarantee that the package will work on all devices without any bug fixing but I think the priority is to avoid duplicating code. 

> (2) I'm still unsure of how to implement the package when the different
> chips have different memory sizes. A quick look through the existing
> hal
> and all I find is hard-coded constants in the pkgconfig files.

One way to workaround that is to keep the memory layout in the board specific package. You can have something like:

lm3s\lm3s6xxx                      -> code common to all 19 chips
lm3s\ek_eagle100\                  -> board specific code
lm3s\ek_eagle100\include\pkgconf\  -> memory layout
 
> For both those reasons, I started wondering if it wouldn't be better to
> either create separate packages for each of the different individual
> chips. That way each package would be relatively small, easy to
> implement, and fully tested when implemented. But that would result in
> over 180 packages just for Stellaris!
>
>
> Then I thought maybe we group the chips by memory sizes, like a package
> called "lm3s256x64" for all the chips with 256k Flash and 64k RAM. But
> that would make it difficult to track chips by part number.
> 
> > Regards
> >
> > John Dallaway
> > eCos maintainer
> > http://www.dallaway.org.uk/john
> >