[OpenTRV-dev] V0p2 Bootloader source

[Jeremy Poulter]

Maybe 3.3v should have been enough power run at 8Mhz, IE not on batteries
;-)

Jerem
On 10 Mar 2016 11:56, "Damon Hart-Davis" <dhd at exnet.com> wrote:

> The very next update I am going to do, uploading new code into a REV7, I
> would have to take the unit apart and make a big effort to power it off
> something other than its internal batteries (2xAA), so the ‘assuming 3.3V’
> thing would not work for me!
>
> And only some of our boards present ICP connections (ie SPI), though it is
> nominally available on most newer boards.
>
> I agree that 4800 can be tedious, and it presents me with other issues too.
>
> Rgds
>
> Damon
>
>
> > On 10 Mar 2016, at 11:51, Jeremy Poulter <jeremy at bigjungle.net> wrote:
> >
> > Hi,
> >
> > I was only thinking about doing this when uploading a new firmware,
> doing this at 4800 is a bit tedious. So I think we can make a reasonable
> assumption that the full 3.3v is available so should be able to get the
> full 8MHz. Or do you normally use an ISP to update the firmware?
> >
> > Jeremy
> >
> > On 10 Mar 2016 11:33, "Damon Hart-Davis" <dhd at exnet.com> wrote:
> > Hi,
> >
> > > On 10 Mar 2016, at 09:47, Jeremy Poulter <jeremy at bigjungle.net> wrote:
> > >
> > > Where might I find the source for the bootloader? I wanted to see if I
> could increase the upload speed. You should be able to set the CPU to 8MHz
> for programming and upload at 38400 baud.
> >
> > Can only hit 8MHz if running off a 3.3V (well 2.7V+ IIRC) supply, ie not
> for our 2xAA-powered devices.  At the bottom of our supply voltage range
> 4MHz may be OK, 2MHz would possibly be more reliable.  And note that 1MHz
> is the factory-standard rate for a fresh AVR.
> >
> > Faster UART is probably only a good idea at the higher voltages and CPU
> clock rates, so would not work with all deployments.
> >
> > I *was* contemplating boosting the CPU speed to whatever is safe given
> the current supply voltage for such intensive items as the encryption,
> which if used to with the PICAXE.
> >
> > My feeling is that there are bigger fish to fry and with the current
> V0p2 I don’t want to add more options that are non-standard and that would
> add to confusion.
> >
> > Maybe allowing the UART to run at 9600 would at least be allowing
> movement towards a more ‘standard’ rate.
> >
> > As to source, no, see:
> >
> >
> http://www.earth.org.uk/OpenTRV/Arduino/bootloader/ATmega328P-1MHz/README.txt
> >
> > http://arduino.cc/forum/index.php/topic,160647.msg1204176.html
> >
> > A new bootloader built from source (though we have to be careful about
> licensing) might also allow us to write to Flash for such sensitive data as
> secret keys, with fuses set to prevent reading them out again with
> different code.
> >
> > But maybe these are things we could consider for a V0p3...
> >
> > Rgds
> >
> > Damon
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