What should be the maximum size of a variable that we can use

[Pavan kumar]

Hi all, In my project I have a structure its length was about 2KB, I'm saving it as a static variable after using this I come across with a weird behavior from the board, Some times its hang up when I gets disconnected from the phone, and I'm able to resolve that by changing the compiling order of .c files in makefile(not sure how could it effect). And now I'm seeing it works fine if I don't write data to uart and getting hang when I'm writing data through uart,

I felt like it may be because of some segfault(correct me if I'm wrong). And I'm really wonder to know what should be the maximum size of a static variable that we can use in a project

PS: My board configurations were nrf51822 with 16KB of RAM and 256KB of flash and I'm using SDK11 on the board I'm using 2KB for stack and 0bytes for Heap

I'm attaching my .map files. My code with this mapfile1.map mapfile getting hanged on disconnected, and code with this mapfile mapfile 2.map resolves issue when disconnects but getting hanged on writing data to uart

The only change that I made for both two is changing the order of .c files in makefile like order1.png to order2.png no changes in code

here is my sensor_conditioner.c and custom_app_uart_fifo.c

EDIT: I did some sort of debugging and found the reason for crashing the app is because of changing value of a variable that storing call back handler address m_application_table[0].ntf_cb but not sure how could it happens. I'm attaching my results,

We can observe before calling the function ble_sh35_update_sat_temp(), m_application_table[0].ntf_cb points to a valid call back address 0x1d4f5 but just after calling that function the value getting changed to 0x20001d04 this value keep on changing while tracing and points to some undesired location, that's why when I disconnected from the phone it should call this call back function but it encounters a hard fault can any one understood what should be the reason for it and for small info m_application_table located at address 0x200035B4 in my map file and end address of RAM is 0x20004000 and the start address of RAM is 0x20003800

Thanks in advance

[Hung Bui]

@Pavan: I don't think there is a limit of the max size of a static structure instance except for the limit of the actual application RAM size allocated. As far as I understand the static variable will be located in .data in RAM, not the stack.

nRF51822 with 16kB RAM is pretty limited and could be that you already over run the RAM size. Note that some function requires aligned address, check if it's your case.

Could you send the project ? Or at least the .map file after you compile.

[Pavan kumar]

Thanks for reply Hung I'm attaching my mapfile and the order that I used in makefile to compile them. Please check them

[Hung Bui]

Could you tell the variable name of the struct that has 2kB size ?

What exactly happened when it crashed ? Have you tried to put a break point in app error handler ?

Maybe you want to send me the custom_app_uart_fifo.c and the sensor_conditioner.c

Have you check the RAM usage ? if you use more RAM the chip has ?

[Pavan kumar]

The name of the variable is pstorage_data, Nothing happens when I connected from phone and write data to uart Its crashed and disconnected from phone and not advertising I need to reset the board to get that back, That's why I felt its segfault. I don't know how to check the RAM usage I used linker script that says RAM address will be

MEMORY { FLASH (rx) : ORIGIN = 0x1b000, LENGTH = 0x25000 RAM (rwx) : ORIGIN = 0x20002180, LENGTH = 0x1e80

APP_VERSION_ADDRESS (rw) : ORIGIN = 0x29FFC, LENGTH = 0x04 }

[Pavan kumar]

And I attached my files to the post custom uart doesn't do much than it will only have some more baudrates support like #define UART_BAUDRATE_BAUDRATE_Baud90000 0x0170A3D7UL /**< 90000 baud. */ Its for 90K and in sensor conditioner will read data using UART and on the first byte it starts a timer and after timer expires it read the buffer and extract the data