changing code from 16F to 18F microprocessor

[SCC_699]

Do I need to define / configure all of the ports on the chip or just the ports used in the program? I don't recall defining the ports that way for the 16f and it seemed to compile fine and run well except for the wide range in the counts from the timer loop.

[sougata]

Hi,

Have you tried with MPASM ? Could you actually locate the "18F2620.INC" . Default configurations are always there. So I seriously doubt why the program would not compile and issue configuration error. Here it does compile okay.

[Acetronics2]

Do I need to define / configure all of the ports on the chip or just the ports used in the program? I don't recall defining the ports that way for the 16f and it seemed to compile fine and run well except for the wide range in the counts from the timer loop.

Hi,

The compiler did it for you ... as your first projects were using the DEFAULT config provided !!!
For "bigger" chips the compiler DEFAULT config lines are not so numerous as the offered features ... it's you to define what you want !!!

You, of course, have to define all ports as I or Os , and initialize them ... if you do not want to get unexpected behaviour.

May be a "midrange" series chip as a second one ( if i understood your post ...) as a 16F628, 16F648 ,16F876a or 16F877a could help for the transition ... with their "limited bunch" ( lol ! ) of peripherals ...

Alain

[SCC_699]

Alain Thanks for the reply. I would like to use the pic16f877 (since I have a few onhand) but I was concerned it would behave similar to the 16f84a that I am currently using.

I was experiencing a large variation in the incremented variable despite the fact that the time between the sensors was very precise. (I use the raw counts in a flow calculation.) The actual time between the sensors varies from 2 - 5 seconds depending on the flow. The raw counts for the variable (value) are approximately 33,000 for 1 ml/min flow. The variablity was more than 25% between successive measurements and I also observe a decay in the counts.

I thought a chip with more capacity would help. I realize now that it is a large leap from one to the other since I will have to rewire the processor board to the 18f pinout.

If there is a chip you could recommend that would meet the data and calculation needs while trimming down the unused peripherals that would be appreciated as well.

Thanks

[Ioannis]

I think the closest to F877 is the 18F452. It is pin to pin compatible and has twice the memory. Once I remember porting the almost 7,5K of program directly to the F452 with a couple of DEFINEs on top. Piece of cake.

Ioannis

[skimask]

I think the closest to F877 is the 18F452. It is pin to pin compatible and has twice the memory. Once I remember porting the almost 7,5K of program directly to the F452 with a couple of DEFINEs on top. Piece of cake.
Ioannis

Agreed 100%.
Started out a project a long time ago on a 16F877A. Ran out of memory, plugged in an 18F452, changed a couple of define's, a few register settings, ran great. Ran out of memory again, plugged in an 18F4620, changed a few more register settings...Same program, ran like a champ (then ran out of code space again, built up an 80pin TQFP-> 40 pin DIP adapter for an 18F8722, plugged it in, changed 1 or 2 register settings, doubled the code space, ran great again).

[Ioannis]

Agreed 100%.
Started out a project a long time ago on a 16F877A. Ran out of memory, plugged in an 18F452, changed a couple of define's, a few register settings, ran great. Ran out of memory again, plugged in an 18F4620, changed a few more register settings...Same program, ran like a champ (then ran out of code space again, built up an 80pin TQFP-> 40 pin DIP adapter for an 18F8722, plugged it in, changed 1 or 2 register settings, doubled the code space, ran great again).

... then run out of memory again and plugged a ... x86 core 2 with 2gb of memory!

Ioannis

[skimask]

... then run out of memory again and plugged a ... x86 core 2 with 2gb of memory!
Ioannis

I could run the 18F8722 in external mode and 2GB of flash....and skip the Core2 altogether

But that's what I get when I kept adding crap on top of crap on top of crap
I went thru the code awhile back and tried a fair amount of optimizing. Turns out I could've stuck with the '452 if I'd have just been a bit more diligent in the code writing in the first place.

[Acetronics2]

I thought a chip with more capacity would help. I realize now that it is a large leap from one to the other since I will have to rewire the processor board to the 18f pinout.

If there is a chip you could recommend that would meet the data and calculation needs while trimming down the unused peripherals that would be appreciated as well.

Thanks

Hi, You can try the 18F1320 instead of a 16F84 ... pinout is COMPATIBLE ( care ... pins names are not the same !!! ... so you only have to rename them . )

Alain