Where's the rest of the internal memory?

[vonnieda]

I started to run into some memory issues in my project this morning, so I am spending some time debugging memory. I noticed there seems to be less internal memory than the datasheet indicates and am wondering how to access it.

I'm using a WROVER32KIT v3 and if I build the following tiny app, it reports "227560" on startup.

Code: Select all

#include "sdkconfig.h"
#include "esp_system.h"
#include "esp_log.h"

#define TAG "TEST"

void app_main()
{
	ESP_LOGI(TAG, "%d", esp_get_free_heap_size());
}

The datasheet says that the ESP32 has "520 kB (8 kB RTC FAST Memory included) of on-chip SRAM for data and instructions." So where is the other 290k hiding, and is there a way to use it?

FWIW: I'm aware of the SPI RAM, and am using it in my project. This came about because I ran out of internal RAM specifically when allocating FreeRTOS task stacks.

Thanks in advance for any light you can shine!

Thanks,
Jason

[WiFive]

Code: Select all

heap_caps_get_free_size(MALLOC_CAP_8BIT)
heap_caps_get_free_size(MALLOC_CAP_32BIT)

First will show DRAM, second will show DRAM+IRAM

[vonnieda]

Code: Select all

heap_caps_get_free_size(MALLOC_CAP_8BIT)
heap_caps_get_free_size(MALLOC_CAP_32BIT)

First will show DRAM, second will show DRAM+IRAM

Thank you for the response WiFive, but I'm still not seeing the full amount. Here's the new test program and output:

Code: Select all

#include "esp_system.h"
#include "esp_log.h"
#include "esp_heap_caps.h"

#define TAG "TEST"

void app_main()
{
    ESP_LOGI(TAG, "MALLOC_CAP_8BIT %d", heap_caps_get_free_size(MALLOC_CAP_8BIT));
    ESP_LOGI(TAG, "MALLOC_CAP_32BIT %d", heap_caps_get_free_size(MALLOC_CAP_32BIT));
}

I (256) TEST: MALLOC_CAP_8BIT 299304
I (256) TEST: MALLOC_CAP_32BIT 395940

So it seems like there is at least another 124k missing?

[ESP_igrr]

There is also statically allocated memory (both IRAM and DRAM), you can see the amount by running "make size". Plus a 64kB region of IRAM used for CPU caches.

[vonnieda]

There is also statically allocated memory (both IRAM and DRAM), you can see the amount by running "make size". Plus a 64kB region of IRAM used for CPU caches.

Thank you ESP_igrr, I think that clears it up for me. If I add up all those numbers I get close enough to 520k.

Thanks,
Jason