I'm using SDK17.0.2
I need to keep a noinit variable in memory so that I have the correct flag when I execute the DFU. So I use the following method, but it doesn't seem to work
I defined a noinit area for the end of memory in the .sct file
LR_IROM1 0x00026000 0x0005A000 { ; load region size_region
ER_IROM1 0x00026000 0x0005A000 { ; load address = execution address
*.o (RESET, +First)
*(InRoot$$Sections)
.ANY (+RO)
}
RW_IRAM1 0x20002C00 0x0000D3FC { ; RW data
.ANY (+RW +ZI)
}
NOINIT 0x2000FFFC UNINIT 0x00000004 {
.ANY (NOINIT)
}
}
At the same time, the variables are mapped to the address in the main program
uint32_t OTA_mode
__attribute__((section("NOINIT")))
__attribute__((used));
Then I can see the variable location in the .map file
HEAP 0x2000bfa8 Section 8192 arm_startup_nrf52.o(HEAP)
Heap_Mem 0x2000bfa8 Data 8192 arm_startup_nrf52.o(HEAP)
STACK 0x2000dfa8 Section 8192 arm_startup_nrf52.o(STACK)
Stack_Mem 0x2000dfa8 Data 8192 arm_startup_nrf52.o(STACK)
__initial_sp 0x2000ffa8 Data 0 arm_startup_nrf52.o(STACK)
NOINIT 0x2000fffc Section 4 main.o(NOINIT)
__tagsym$$used 0x2000fffc Number 0 main.o(NOINIT)
In the .map file, the address belongs to the Noinit zone
Execution Region NOINIT (Exec base: 0x2000fffc, Load base: 0x00052730, Size: 0x00000004, Max: 0x00000004, ABSOLUTE, UNINIT)
Exec Addr Load Addr Size Type Attr Idx E Section Name Object
0x2000fffc 0x00052730 0x00000004 Data RW 6 NOINIT main.o
After that，I automatically increment the variables and print the values in the main program, with a 500ms delay, and do a soft reset
uint32_t OTA_mode
__attribute__((section("NOINIT")))
__attribute__((used));
void main()
{
log_init();
OTA_mode += 1;
NRF_LOG_INFO("ota_mode:0x%X", OTA_mode);
NRF_LOG_INFO("REG32:0x%X", REG32(0x2000FFFC));
NRF_LOG_PROCESS();
NRF_LOG_PROCESS();
nrf_delay_ms(500);
NVIC_SystemReset();
}
Under normal circumstances, this variable should be self-incrementing. But the logs I actually got look like this
00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1 00> 00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1 00> 00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1 00> 00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1 00> 00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1 00> 00> <info> app: ota_mode:0x1 00> 00> <info> app: REG32:0x1
I'm guessing this piece of RAM is actually reset. I hope I can get some revelations
