Datalogger project

[eye1984]

Hi everyone, I am new in pic and C programming, but i need for my school project to develop a datalogger, which will be inserted in the wall under the switch for lights (so small and for 1 year living from battery). I need it cheap, because I need log that in more rooms so i have chosen 12f675 for its small size and sleep function, pcf8583 for save time and eeprom 24lc512 for storing data. Circuit is in picture, but i need strong help with program. I think the best solution for battery lifetime is that:

1) pic read switch (turned off), read time from pcf8583, enable eeprom by log 1 on GP2, write it to eeprom V:hh:mm/DD:MM, disable pin GP2 to save battery power, sleep procesor/wait for turn on.
2) After switch turned on - wake up procesor, read time from pcf8583, enable eeprom by GP2 , write time to it Z:hh:mm/DD:MM, disable eeprom by GP2 get low, sleep procesor/wait for turn off.

If it will by readable from eeprom by hyperterminal and time/date possible to set up, it will be very comfortable for my research. But microcontrollers are not my specialization and this is only one project for me and to learn for one project complete i2c communication and C programing for pic is too difficult. I have only one month to do that. (If I will not buy datalogger in shop for about 70eur which in 10 rooms mean 700eur).
Because of that i will ask if is here some good soul who have function parts of that what i need (I browsed forum for 3 days and found only little things about intosc and fuses or something about eeprom writing but for another processor). Or if someone will help me with program that stuff.

thx for help

[asmboy]

you need to try to code this and see how far you get.

this is not a resource for doing your creative THINKING for you .

or the homework for that matter, either.

BTW: R Y sure U sized your storage big enough ??

[eye1984]

i don't know if 512kb is enough, but it is the biggest eeprom in my local store.

i am trying it, but after one week i have only blinking led until switch is pressed.
after that i try to implement ex_wakup.c to 12f675 from ccs c, but i think it is not working, i would to blink led on gp4 2 times, after switch is on, and go sleep....but when i use #int_EXT it is not working for me, when i use #int_RA with the same code in routine as in #int_EXT, i think it works but led will not blink 2 times but only once and after switch turned off it again blink only once. this is my code for now:

[asmboy]

OK the code does have a way to go before you are ready to be critiqued on function.

But here is a conceptual thing i wonder about?

you are using an I2C EEPROM that has page or byte mode - lucky it has BYTE mode because your pic has not got enough RAM to buffer a page


But it only has 64K bytes of storage and you said you want perhaps a year of data ... your data format if it was expressed w/o delimiters as ASCII will take 18 bytes for every on/off cycle. thats a total of only 3640 total captures on/off events. Lets stipulate that given a compact binary STRUCT for your data could take less space:

such as V || Z is a single bit
&& that V!Z is the high order bit of a single BYTE conveying the seconds value in binary - && similar compression of the other data.
Then this could be packed in say 12 bytes or less for each full cycle of recorded events .. BUT , thats still only 5460 events or put another way about 15 times ON/off per day that you have space to record.

Is that an amount that will actually be enough?

ALSO - your code must have a bullet proof way of managing and storing the pointer to WHERE the next block of data will be written.

Have you thought about how you will handle your external EEPROM when power is applied - to find out what is written and what is not ?

I am still thinking about your concept for using sleep in between events,
as it may be harder to implement than you think, given your honest admission about your program skills.

[asmboy]

also LOOK AT YOUR SCHEMATIC CLOSELY

where is PIN 2 of the PIC connected --

what does the switch ACTUALLY DO ?????

what do you think >

[asmboy]

also
HOW WILL YOU SET your RTC ????

[eye1984]

How to set up the rtc i don't know, if through pic/rs232 or only leave it unset if it starts counting from power up and correct dates in PC after downloading data from eeprom.
I think that in most rooms there will be on/off cycle for 5-10-times per day maximum, so i think it will be enough.

And thank you for warning, it is mistake, pin2 is connected between SW and resistor of course.

Its everything new for me and that are only ideas how i think it can be done. It is for research lab to make graphs from that data to show how long was turned on lights in every room of building. So at the end i will download data to Excel and make graphs based on months to show how is weather and year seasons influencing to need of light turned on, and for graphs how long people stays in rooms (when light is on) in rooms without windows.

[asmboy]

It is an interesting project - and of a sort that has often been done before.

Getting your data out of the EEPROM ought to be considered before you go a lot further, as well as proper RTC management control.

I would have a super-cap OR memory battery for the RTC
AND perhaps using the RTC user RAM for my "next write pointer".

also

I personally would do this with a higher function PIC
such that there is RS-232 for:

1- setting the RTC
2- playing BACK the EEPROM data
3- design so you can switch the PIC from 32khz RTC mode to Internal 4 or 8 mhz during RS-232 operation with a host

Are you going to seriously produce number of these or just hand in a prototype??

[eye1984]

Only prototype - little series in about 10 pcs. I have selected 12f675 for price, size of only 8 pins and i2c, sleep and low power consumption and internal oscillator for minimum parts. But if it is better solution with bigger pic, it is no problem to change it. Only requirement is that all that parts with 3V battery must be on pcb - round of maximum diameter 5cm.

[asmboy]

You can have it all - including an RS-232 TTL I/O system with twice the program memory in the 12F1822.

Check it out and adjust your schematic.

With this small change you can have external setting of the RTC and a way to play back your data by simply diode coupling and upping your VCC to 5v externally and provide a MAX232 or FTDI UM232 to get a standard EIA RS-232 PC connect or a USB connection - respectively.

[ckielstra]

[ckielstra]

A good suggestion from Asmboy is to use the non-volatile RAM in the clock chip as a storage for the EEPROM write address pointer. Otherwis, if you are not planning on using the clock chip's RAM you could change the PCF8583 for a PCF8563 which has a lower power consumption of typical 0.4uA @ 3V

[asmboy]

[ckielstra]

[eye1984]

today i have searched in all eshops and local stores in my city(eshops in my country) and 12f1822 / 12lf1822 is not possible to buy :(


12f are possible only 12f508/509/510/629/675