water flow meter..

[BigWumpus]

Don't write to often to the EEPROM on the same position !
Think about a ring-buffer !

Maybe:
Get the olf value.
Count...
Write the new value to the next position and a checksum out of the new and the old value (asume a fixed value for non-existing old values!). If you reach the end of EEPROM, begin on the first position.

After Power-On
0: store 0 as backup-value.
1: read a value, check checksum.
2: if checksum is ok, store the value as Backup, goto 1
3: if checksum is bad, use the backup-value and exit

Just read to manual !
Maybe you can build hardware to buffer the pic fpr around 10ms to write the eeprom and then turn off. Use the Brown-Out-Reset !!!!

[BobK]

Hi Ecca,

Can you provide us with some information on the flow meter, such as the manufacturer and part number, perhaps a web site to look at this sensor closer?

Thanks,


BobK

[Darrel Taylor]

For saving to the EEPROM, choose a PIC with a LVD (Low Voltage Detect) interrupt.

When the power is turned off, the interrupt gets triggered, quickly save to EEPROM while the chip is still running on the capacitor charge.

The rest of the time, the value is available in RAM. No need to save it on every loop.
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[mister_e]

Or a comparator interrupt OR modify the power supply. You place a diode between the bridge and the capacitor, then send the bridge side on a interruptable pin.

Just another idea

How many different ways exist to skin a cat?

[Charles Linquis]

The 18F8722 datasheet claims the EEPROM is typically good for a million write cycles. I would probably trust it for 500K cycles.

[ecca]

Right then, having returned from holidays..... I continue.
I only require a 3 digit LCD with about 12mm digits.
What's around at the moment ?
Thanks for help all,
Ecca