Memory allocation?

ezflyr · Joined: 25 Oct 2010 Posts: 1019 Location: Tewksbury, MA

Hi,

Is there a way to see how RAM is being allocated in a project? A file perhaps?

I am working with a 16F648a device and I'm unexpectedly getting a "not enough RAM" error. My code contains two 80 character arrays, and about 10 int8 variables, so the 264 bytes of RAM in the 16F648a should be enough, I think? Am I missing something?

Suggestions?

Thanks!

John

dyeatman · Joined: 06 Sep 2003 Posts: 1931 Location: Norman, OK

Look at the .STA and .SYM files in the same directory as your project.
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ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

ezflyr · Joined: 25 Oct 2010 Posts: 1019 Location: Tewksbury, MA

Hi all,

Thanks for the input!

The addition of the #device *=16 directive did not solve my problem. A look at the .sym file indicates that the compiler is indeed trying to use more RAM memory than I have available.

Let me step back and describe my situation. I am re-writing a GPS NMEA receive routine based on the EX_SISR.c example program (circular receive buffer). Originally, I had the program working nicely with a linear buffer, but in only worked properly when all NMEA messages were turned off except the one I wanted ($GPRMC). I really wanted a more flexible solution, so I decided to implement the circular buffer strategy.

My original program contained a receive buffer of 80 characters. The re-written version uses an 80 character circular receive buffer (written to only allow the desired string to enter), and an 80 character message buffer. Is there a general rule-of-thumb as to how big the circular buffer needs to be relative to the message buffer? Obviously, I want to have the circular buffer long enough to avoid overwriting characters before they can be processed......

Given the description of what I need to accomplish, is my buffer (circular and message) allocation OK? Do I just need to find a PIC with more RAM?

Thanks,

John

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

ezflyr · Joined: 25 Oct 2010 Posts: 1019 Location: Tewksbury, MA

Hi PCM,

I'm not declaring any variables as 'static', so I'm not sure how those threads effect my problem? I believe that the compiler is free to reuse RAM for non-static variables, correct?

As I said, maybe I'm just going about the design of my program incorrectly - I've never implemented a circular buffer before. I've got an 80 character free-running circular receive buffer being filled by my INT_RDA interrupt, and an 80 character message buffer (the NMEA message of interest is about 76 characters long) being processed in Main. Does that sound about right?

So, at least in my mind, I've got two primary questions:

1. Is my program design appropriate, ie. are my buffer allocations reasonable?

2. What is the minimum number of actual RAM locations I need for a correctly designed circular buffer implementation requiring the receipt of a 76 character message?

Thanks,

John