Memory master ram serial number lookup2/13/2024 ![]() Available Heap DRAM Īt startup, the DRAM heap contains all data memory that is not statically allocated by the app. This will allocate memory with the capability MALLOC_CAP_DEFAULT, which is byte-addressable.īecause malloc() uses the capabilities-based allocation system, memory allocated using heap_caps_malloc() can be freed by calling the standard free() function. When calling malloc(), the ESP-IDF malloc() internally calls heap_caps_malloc_default(size). In that case, IRAM can still be used as a "reserve" pool of internal memory if the users only access it in a 32-bit aligned manner, or if they enable CONFIG_ESP32_IRAM_AS_8BIT_ACCESSIBLE_MEMORY). If ran out of MALLOC_CAP_8BIT, the users can use MALLOC_CAP_IRAM_8BIT instead. ![]() Users can call heap_caps_get_free_size(MALLOC_CAP_8BIT) to get the free size of all DRAM heaps. The external RAM is integrated into the ESP32's memory map via the cache, and accessed similarly to DRAM.Īll DRAM memory is single-byte accessible, thus all DRAM heaps possess the MALLOC_CAP_8BIT capability. It is also possible to connect external SPI RAM to the ESP32. If accessed as generic memory, all accesses must be aligned to 32-Bit Accessible Memory.ĭ/IRAM is RAM that is connected to CPU's data bus and instruction bus, thus can be used either Instruction or Data RAM.įor more details on these internal memory types, see Memory Types. IRAM (Instruction RAM) is memory that is connected to the CPU's instruction bus and usually holds executable data only (i.e., instructions). ![]() This is the most common kind of memory accessed as a heap. The ESP32 contains multiple types of RAM:ĭRAM (Data RAM) is memory that is connected to CPU's data bus and is used to hold data. If you want to have a memory with certain properties (e.g., DMA-Capable Memory or executable-memory), you can create an OR-mask of the required capabilities and pass that to heap_caps_malloc(). However, in order to fully make use of all of the memory types and their characteristics, ESP-IDF also has a capabilities-based heap memory allocator. A capabilities-based memory allocator allows apps to make heap allocations for different purposes.įor most purposes, the C Standard Library's malloc() and free() functions can be used for heap allocation without any special consideration. See xTaskCreateStatic() for the alternative where stacks are statically allocated.īecause ESP32 uses multiple types of RAM, it also contains multiple heaps with different capabilities. By default, each of these stacks is allocated from the heap when the task is created. ESP-IDF applications use the common computer architecture patterns of stack (dynamic memory allocated by program control flow), heap (dynamic memory allocated by function calls), and static memory (memory allocated at compile time).īecause ESP-IDF is a multi-threaded RTOS environment, each RTOS task has its own stack.
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