[sdiy] Retaining button state after power off?

Roman Sowa modular at go2.pl
Sat Feb 1 23:20:13 CET 2014

I was refering to power cycles of the entire device and not each button 
press, because the clean way to do it is to write last config state when 
power is actually being turned off. PIC monitors power line, and if it 
drops below some threshold, it initiates EEPROM write, which takes about 
3ms. Power lines usually don't drop nearly that fast so it will be 
finished before the raill goes to, say, 2V. That's why insane daily 
rebooting gives 100 years, while more civilized use means impossible to 
imagine 1000 years of operation.

And as a side note about Polysixes, as I did a few myself - always 
replace the NiCad with a socket for CR2032. That one does not leak, and 
works for decades. I have seen 30-year old synths with lithium battery 
still in fair condition. So battery is not a bad thing in general, NiCad is.


W dniu 2014-02-01 19:07, Tom Wiltshire pisze:
> I agree with Roman. The 12F EEPROM has an expected life of 1,000,000
> writes, so if you write the current setting to the EEPROM every time
> you press one of the buttons, most cheap buttons will fail before the
> EEPROM does. Of course, if you put expensive MEC buttons on it
> (10,000,000 operations expected life) then you probably will have to
> replace the uP at some point, if the rest of it hasn't died by then.
> It's an odd world we live in when a whole computer on a DIP costs
> less and takes up less space than a couple of flip-flops, but that's
> how it is.
> Personally, I don't like the CMOS+batteries idea, but then I've seen
> the inside of too many Polysixes. Ugh. Who'd want to add that feature
> to their design?!
> T.
> On 1 Feb 2014, at 16:26, Roman Sowa <modular at go2.pl> wrote:
>> With typical PIC12F family EEPROM endurance and ridiculous 20 daily
>> reboots of the device you still have way more than 100 years before
>> having to worry about endurance. And by that time the circuit will
>> be long dead because of dried capacitors, solder whiskers, dust,
>> humidity, worn out pots and switches, and electrostatic discharge.

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