[OpenTRV-dev] V0p2 Bootloader source

Jeremy Poulter jeremy at bigjungle.net
Thu Mar 10 11:51:22 GMT 2016


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?

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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