Lpc2000

Guillermo Prandi wrote:

>If you use 'const', they will stay in flash, rest assured.
>
>  
>
Ah, thanks, so all I have to do is assume that if I put "const" on the 
structure tag then it will go into Flash...  Hmmm....

I prefer to check those things out, like looking inside the lst file on 
occasion and surveying what the compiler is doing.

Regards,

TomW










>This is my compile command for 'console.c' (not using thumb, just 
>ARM):
>
>gcc -c -mcpu=arm7tdmi -I. -gdwarf-2 -DREENTRANT_SYSCALLS_PROVIDED
>-DROM_RUN -DGCC_ARM7 -I ./include -O2 -Wall -Wcast-align
>-Wimplicit -Wwrite-strings -Wpointer-arith -Wswitch -Wreturn-type
>-Wunused -Wshadow -Wa,-adhlns=lib/console.lst
>-fmerge-constants -IARG -IARG/include -MD -MP
>-MF .dep/console.o.d -Wstrict-prototypes -Wmissing-declarations
>-Wmissing-prototypes -std=gnu99 lib/console.c -o lib/console.o
>
>And this is the linker command for the 'project' executable:
>
>gcc -mcpu=arm7tdmi -I. -gdwarf-2 -DREENTRANT_SYSCALLS_PROVIDED
>-DROM_RUN -DGCC_ARM7 -I ./include -O2 -Wall -Wcast-align
>-Wimplicit -Wwrite-strings -Wpointer-arith -Wswitch
>-Wreturn-type -Wunused -Wshadow -Wa,-adhlns=build/crt0.lst
>-fmerge-constants -MD -MP -MF .dep/project.elf.d
>build/crt0.o lib/console.o --output project.elf -nostartfiles
>-Wl,-Map=project.map,--cref  -lc  -lm -lc -lgcc
>-Tbuild/LPC2138-ROM.ld
>
>The -Map=project.map option will output the map file. The --cref 
>addition will output the final assembler listing (.lss). I don't 
>recall which of these linker options will give you the project.sym 
>file. In this file (.sym) you will be able to see whether your 
>variable will reside in flash or in RAM: flash addresses are below 
>0x00080000, whilst RAM addresses will be between 0x4000000 and 
>0x40007fff. Also, a letter before the symbol name will give you the 
>name of the section where they will be placed (t=.text, d=.data, 
>b=.bss). For example, these are tables that will reside in flash 
>(.text):
>
>0001ca4c t hex
>0001ca60 t leds.1409
>0001ca78 t badptr.1408
>0001ca88 t SectorsByCPU
>0001caa0 t LPC2138sectors
>0001cbf0 t cOffPat
>0001cbfc t LED_Bits
>
>These are tables that will be copied to RAM at system startup (.data):
>
>40000014 d sGPSMaxWait
>40000018 d sGPSMinSats
>4000001c d sGPSMinData
>40000020 d sGPSOffDuty
>40000024 d sGPSOnDuty
>
>Finally, these are variables that will be zero-filled and reside in 
>RAM from start (.bss):
>
>40001e00 b sNextAction
>40001e04 b sMainShutDown
>40001e08 b sMainThreadHandle
>
>
>The t, d, and b flags come also in uppercase flavor, although I don't 
>know what is the difference between t and T, d and D or b and B.
>
>All this is provided you start from 'standard' crt0.asm and .ld 
>scripts, like those from the WinARM or FreeRTOS examples for gcc.
>
>Guille
>
>--- In lpc2000@yahoogroups.com, G B <microsys@...> wrote:
>  
>
>>That's the ticket!
>>
>>How can you tell the compiler to put the string in flash?
>>
>>Glen
>>
>>
>>Guillermo Prandi wrote:
>>    
>>
>>>Hi, Sean. From tests I did with GCC 4.0.1, I came into the 
>>>      
>>>
>conclusion 
>  
>
>>>that:
>>>
>>>char* test1 = "TEST1"; <--- doesn't get copied to RAM
>>>char  test2[] = {'T','E','S','T','2'}; <--- does get copied to 
>>>      
>>>
>RAM.
>  
>
>>>i.e., omiting the const modifier is not enough to make strings be 
>>>copied to RAM. Strings declared with double quotes are considered 
>>>const whether we say so or not. There are options to explore 
>>>      
>>>
>besides 
>  
>
>>>this. For instance, you can specify the section where you want 
>>>      
>>>
>your 
>  
>
>>>variable placed (.text, .data, etc.); I did no tests with that.
>>>
>>>Guille
>>>
>>>      
>>>
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> 
>Yahoo! Groups Links
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-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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