Writing to flash in a mesh application

Question

I would like to use the flash in legacy way. My application collects data in small chunks and I would like to store it in a continuous area. 
 The recommended flash manager is not suitable, because the data stored with header. This is not what I need. 
 The fsorage works fine as long as the mesh stack is not started. After start I get timeout because of the well known timeslot problem. Can I somehow pause the mesh before the flash operation? 
 The nrf_nvmc and nrfx_nvmc does not work, I get application memory access error. I tried to write to addr 0x4A000. My linker file don't use this area. Why do I get this error? 
 Is there any way to use some part of the flash as a continuous storage area?

Peter Gombos · Answer

Hi Marjeris! 
 Thank you for the answer. 
 As I mentioned in my first post, the flash manager is not able to store more than 128 bytes records. Moreover it is not able to merge small chunks into larger area. Finally to store 4 byte long data uses extra 4 byte header. This is not what I need. 
 I found a working solution while studying the flash manager implementation. Here is the sniplet: 
 #include "flash_manager_internal.h"

static void* get_address(uint32_t offset)
{
 return (void*)(0x4A000 + offset);
}

ret_code_t fs_write(const uint32_t offset, const uint32_t* data, const uint32_t len)
{
 uint16_t token = 0;
 flash_operation_t op;

 op.type = FLASH_OP_TYPE_WRITE;
 op.params.write.p_start_addr = get_address(offset);
 op.params.write.p_data = data;
 op.params.write.length = len;
 return mesh_flash_op_push(MESH_FLASH_USER_APP, &op, &token);
}

ret_code_t fs_erase(const uint32_t offset, const uint32_t len)
{
 uint16_t token = 0;
 flash_operation_t op;

 op.type = FLASH_OP_TYPE_ERASE;
 op.params.erase.p_start_addr = get_address(offset);
 op.params.erase.length = len;
 return mesh_flash_op_push(MESH_FLASH_USER_APP, &op, &token);
}
 
 Seems stable. A completion callback can be set also for user MESH_FLASH_USER_APP. The address and length must be 32 bit word aligned in write and flash page aligned in erase. Reading is simple using pointers. Make sure the pages are not protected by BPROT->CONFIG registers. 
 What do you think about this solution? Is it safe? Any disadvantage?