[OpenTRV-dev] V0p2 Bootloader source

[Damon Hart-Davis]

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