Data logger clock and array

[skimask]

Let's say I use interrupt for 1 second using 16bit timer. 8mhz / 4 cycles / 16bit timer 65536 = 0.000030517578125 multiply by 256 prescaler = 0.0078125. 1 second / 0.0078125 = 128. As I understand it should interrupt the software 128 times per second. How do I figure it out if it will not conflict during ADC, CCP, EEPROM, CCP sampling, writing and erasing? I know I can disable interrupt routine during any of these sampling but it'll mess up the time. Is it even possible to do that without external RTC?

8Mhz / 4 = 2Mhz...
Clocking a 16 bit timer off the instruction clock @ 2Mhz = 2Mhz / 65536 = 30.517578125 interrupts per second (have to take the 1/x of the result, that's the part you forgot).
Set up the interrupt routine to count to 30, then take a sample. Yes, you'll be 16.69ms off for each second, unless you reload that particular timer at each interrupt with a correction factor to make it exactly one second. Look up the phrase PIC Multi-Calc.
If you clock an 8 bit timer off the instruction clock @ 2Mhz, 2Mhz / 256 = 7812.5 interrupts per second. Set up that interrupt routine to count to 7812, then take a sample. With the 8 bit timer, you'll only be 65us off in each second.

[Macgman2000]

Ok, I have been watching this thread and I have to jump in. I understand that every gram counts in an RC chopper, I have built some from scratch. The dead bug approach to soldering the PIC without a circuit board is not a good idea. I suggest you take as thin a pcb as possible, use a 16F88 or something with 18 to 20 pins in a SSOIC package, ICP setup will be your best option. You can then buy from RFM or similar an ASK 4mm square surface mount 900Mhz TX. You can then assemble all of these components and it should not weight more 5gm. I know because I have done it. The RX side is an ASK receiver connected to a serial port on your pc. TX every 1sec and log it on laptop PC, write your own app or buy an app, there are lots out there. My advise is intended to save you hours of wondering why things don't work.

Nick

[PicLearner]

Ok, I have been watching this thread and I have to jump in. I understand that every gram counts in an RC chopper, I have built some from scratch. The dead bug approach to soldering the PIC without a circuit board is not a good idea. I suggest you take as thin a pcb as possible, use a 16F88 or something with 18 to 20 pins in a SSOIC package, ICP setup will be your best option. You can then buy from RFM or similar an ASK 4mm square surface mount 900Mhz TX. You can then assemble all of these components and it should not weight more 5gm. I know because I have done it. The RX side is an ASK receiver connected to a serial port on your pc. TX every 1sec and log it on laptop PC, write your own app or buy an app, there are lots out there. My advise is intended to save you hours of wondering why things don't work.

Nick

Thank you for your advice. The project is not intended to be for sale but it is just for fun and learning experience. I've been learning Microchips for the past couple of month and it is very hard for me but every day I learn something new from reading the forum. The whole point of the project just to make it work. Will I even use it in the future? I don't know but it is a lot of fun just to build it and make it work the way I want to. Like I said it's fun to learn something new.

[PicLearner]

8Mhz / 4 = 2Mhz...
Clocking a 16 bit timer off the instruction clock @ 2Mhz = 2Mhz / 65536 = 30.517578125 interrupts per second (have to take the 1/x of the result, that's the part you forgot).
Set up the interrupt routine to count to 30, then take a sample. Yes, you'll be 16.69ms off for each second, unless you reload that particular timer at each interrupt with a correction factor to make it exactly one second. Look up the phrase PIC Multi-Calc.
If you clock an 8 bit timer off the instruction clock @ 2Mhz, 2Mhz / 256 = 7812.5 interrupts per second. Set up that interrupt routine to count to 7812, then take a sample. With the 8 bit timer, you'll only be 65us off in each second.

Oh my god, it looks so much simpler after you explained it to me. I've been reading about the timer and I still was wrong but after your explanation it is so clear to me now. Thank you!!!!!!! Just to make sure about prescaler. For example using 16bit timer with a prescaler 1:1 it would interrupt approximately 30 times per second and using prescaler 1:2 it should interrupt approximately 60 times. Is it correct?

I was just reading thread about instruction execution time by Darrel Taylor and after testing I can easily calculate what it takes to do ADC, CCP, etc. Probably I can even make a simple software clock and add to the clock execution time to compensate missing nanoseconds/milliseconds. I think interrupt clock is much easier and faster to write but what would you recommend interrupt or software clock?

[skimask]

For example using 16bit timer with a prescaler 1:1 it would interrupt approximately 30 times per second and using prescaler 1:2 it should interrupt approximately 60 times. Is it correct?

Nope...

Scaler = Divider, prescaler = predivider, postscaler = postdivider

I was just reading thread about instruction execution time by Darrel Taylor and after testing I can easily calculate what it takes to do ADC, CCP, etc. Probably I can even make a simple software clock and add to the clock execution time to compensate missing nanoseconds/milliseconds. I think interrupt clock is much easier and faster to write but what would you recommend interrupt or software clock?

Must've missed my suggestion to search for PIC Multi-Calc...
If you're using interrupts, you don't have to count the ADC, the CCP, any of that. The interrupt will INTERRUPT every xxx microseconds (or instruction cycles, whatever) and run the interrupt subroutine. Look in the PBP manual under ON INTERRUPT, or if you're feeling froggy, search here for Instant Interrupts.
And think about this...do you really need an exact 1 second interrupt? I'd just concentrate on getting it all working first, then add in some interrupt routines.