[sdiy] Retaining button state after power off?

[Ove Ridé]

On 2 February 2014 07:46, cheater00 . <cheater00 at gmail.com> wrote:
> Hi Ove,
>
> On Sun, Feb 2, 2014 at 1:56 AM, Ove Ridé <nitro2k01 at gmail.com> wrote:
>> On 1 February 2014 08:34, Ullrich Peter <Peter.Ullrich at kapsch.net> wrote:
>>> Yes, an ATTiny35, 45 oder even 12 or 13 could do the job also quite nice, but you have to take care of the maximum write endurance... If you have lots of writes then the FRAM based MSP430 types could help... Nearly unlimited writes possible there...
>>>
>>
>> The ATTiny EEPROM is speced at 100k write/erase cycles, possibly more
>> than the switch. With some clever programming, you could also program
>> one byte at a time, so you'll only consume one write/erase cycle per,
>> say 256 writes, for a 256 byte EEPROM device. You start from the fully
>> erased state, then for each button press, you write 00 to the next
>> available byte in EEPROM. The state is the number of 00 bytes mod 4.
>> When all bytes are 00 and the user presses the button again, the
>> program issues an erase. That should give you an expected 25.6 million
>> button presses.
>
> You're really high-balling it here. If he only ever uses the 4th
> setting, then it's going to be 256/4 * 100000 = 6.4 million. What if
> the user presses the button 6400001 times and it suddenly doesn't work
> - are you going to fix his synth, Ove? Such irresponsible advice.
>
> ;-)
>
> D.

<snarky mode>
If the user only ever uses the 4th setting, I suspect he will never
press the button.
</snarky mode>

-- 
/Ove

Blog: <http://blog.gg8.se/>

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