I'm trying to upload a hex file, generated from multiple C source files with
xc8 in Proteus, into a PIC18F4520. Usually, I don't have any problems doing this but yesterday I ported some Arduino TFT display code to the PIC and tried to upload and test some basic screen functions. The HEX was uploaded and the PIC drove the screen perfectly except for a problem with the colour of text. I went through the code and found the problem was due to a variable that I accidentally declared as
uint8_t instead of
uint16_t thereby causing the colour to be truncated. The variable is one of a bunch of
static variables with file scope:
static uint8_t _width = ST7735_TFTWIDTH; static uint8_t _height = ST7735_TFTHEIGHT; static uint8_t rotation = 1; static uint8_t cursor_y = 0; static uint8_t cursor_x = 0; static uint8_t textsize = 1; static uint8_t textcolor = 0xFFFF; // this is the relevant line static uint8_t text_wrap = 1; static uint8_t colstart = 0, rowstart = 0;
I corrected the declaration and built a new HEX in Proteus and tried to re-upload with the PICkit 2 application. When I imported the hex file to begin the upload, I got the warning:
Hex file loaded is larger than device, which didn't make any sense since the memory summary is:
Memory Summary: Program space used 17DBh ( 6107) of 8000h bytes ( 18.6%) Data space used 6Dh ( 109) of 600h bytes ( 7.1%) Configuration bits used 7h ( 7) of 7h words (100.0%) EEPROM space used 0h ( 0) of 100h bytes ( 0.0%) ID Location space used 8h ( 8) of 8h bytes (100.0%) Data stack space used 0h ( 0) of 580h bytes ( 0.0%)
xc8 output in MPLABX this time, I found this message at the bottom:
Warning: C:/.../train85.X.production.hex contains code that is located at addresses that do not exist on the PIC18F4520. This correlates with other answers I found online; it seems code is being written to non-existent addresses. The methods used by others to solve it seem varied: some made changes to the arrangement of CONFIG variables, making them more compact (which I've tried) while others edited the HEX itself manually. Some observations that may be pertinent:
- If I undo that single correction to the declaration above, the warning is no longer present.
- There are 2 large arrays for font details, that are stored in program memory with the
constkeyword. They are about 2.4k in size and are accessed through pointers in structs.
- If I move one of the font arrays to data memory by removing the
constqualifier, the warning also goes away.
- When I ignored the warning and uploaded the HEX to the PIC with the PICkit application, there didn't seem to be any problems; the TFT display was driven perfectly and the text colour issue was solved.
The HEX, SYM, MAP and startup ASM files, pre- and post-correction, are located here in case you need them. I can't post my code here as there are several files, but I can provide a link to it, if necessary.
In case my question wasn't clear, I need to know the exact cause of the warning, as it relates to my code (HEX) and a solution to it. Is it safe to ignore it, like I did? Thanks in advance.