const array - 'auto' compile error ?

Technical Programming
1

I have this User Code in OperatorControl immediately after the Variable block:


rom const unsigned char L3] = {000,001};

There is a compile error “local ‘L3’ in program memory can not be auto”. This is just a test before I use larger arrays - what’s wrong with the code?

2

I think the error message means that I can’t declare a const there because only automatic local variables are allowed. If only I could add a User Code block between Globals and Begin in Main! Guess it’s time to read the manual.

3

I got the same error, I just removed the rom classification to make it work.

4

Wouldn’t this make it be stored in RAM, not ROM? I think the purpose of putting it in ROM is because there isn’t enough room in RAM…

Just speculating, haven’t actually tried it.

Jacob

5

Removing the word rom, and with an array of length 256 (unsigned char) I get this error:

stack frame too large

So I don’t think that is creating the array in program space? Smaller arrays do compile.

6

mmmm…

I think you have a total of 254 chars, including the ones you use in your program. I just seem to remember this number. I could be completely off the mark.

Jacob

7

This will not work:

 rom const unsigned char L3] = {000,001};

This will work:

 rom const unsigned char L3[2] = {000,001};

You have to tell the compiler the size of the array in ROM data space.

Mike

8

I changed my code:


rom const unsigned char LUT4[256] = {000,003,006,009,012,014,017,020,023,025,028,030,033,035,038,040,042,044,047,049,051,053,055,057,059,061,063,065,067,069,070,072,074,076,077,079,080,082,083,085,086,088,089,090,092,093,094,095,096,098,099,100,101,102,103,104,105,106,107,108,108,109,110,111,111,112,113,114,114,115,116,116,117,117,118,118,119,119,120,120,121,121,121,122,122,122,123,123,123,124,124,124,124,125,125,125,125,125,125,126,126,126,126,126,126,126,126,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,128,128,128,128,128,128,128,128,129,129,129,129,129,129,130,130,130,130,131,131,131,132,132,132,133,133,133,134,134,135,135,136,136,137,137,138,138,139,140,140,141,142,143,143,144,145,146,146,147,148,149,150,151,152,153,154,155,156,158,159,160,161,162,164,165,166,168,169,171,172,174,175,177,178,180,182,184,185,187,189,191,193,195,197,199,201,203,205,207,210,212,214,216,219,221,224,226,229,231,234,237,240,242,245,248,251,255};

Still didn’t work for me, but maybe I don’t have the code in the right part of the project. Where should the code go? Seems like it can’t be in a User Function, and there is no way to enter it in Main…Globals and there is no way to add User Code to Main. I’m sure I could get it to work in MPLAb, but Easyc Pro is fighting me.

9

I did not realize you are using easyC. I am not sure how to work in that environment.

In MPLAB, it would go before the first function call in the file.

10

One way that works with easyC Pro to use the new C source file feature that was just added this year.

Create a source file (go into the project tab, right click “Source Files” and create a file). In there put the definition of the array with the initialization:

rom const unsigned char L3[2] = {000,001};

Then edit the file UserInclude.h and insert an extern declaration for the array like this:

extern rom const unsigned char L3];

Now you can use references to the L3 array in assignment statements or other expressions throughout your block-based easyC program. The only problem is that the array will not show up in the list of variables when you are creating expressions.

11

Thanks Brad. That did the trick.