I’m struggling with an ESP32 library.
As premise, the ESP32 module I’m using has a 2 MB PSRAM on-board.
I wrote a test code to verify it’s working:

void setup()
{
  Serial.begin(115200);
  while (!Serial);

  log_i("Available PSRAM: %lu bytes", (long unsigned int)ESP.getFreePsram());
  uint8_t *b = (uint8_t*)ps_calloc(655350, sizeof(uint8_t));
  log_i("Available PSRAM: %lu bytes, %p", (long unsigned int)ESP.getFreePsram(), b);
}

this is the output:

[   314][I][main.cpp:98] setup(): Available PSRAM: 2095103 bytes
[   365][I][main.cpp:100] setup(): Available PSRAM: 1439735 bytes, 0x3f800800

the memory is then allocated (even with 18 bytes more, I guess for some overhead).
In the library there is the very same code, line #43:

size_t AudioBuffer::init() {
    if(m_buffer) free(m_buffer);
    m_buffer = NULL;
    if(psramInit() && m_buffSizePSRAM > 0) { // PSRAM found, AudioBuffer will be allocated in PSRAM
        m_f_psram = true;
        m_buffSize = m_buffSizePSRAM;
        m_buffer = (uint8_t*)ps_calloc(m_buffSize, sizeof(uint8_t));
        m_buffSize = m_buffSizePSRAM - m_resBuffSizePSRAM;
    }
    if(m_buffer == NULL) { // PSRAM not found, not configured or not enough available
        m_f_psram = false;
        m_buffer = (uint8_t*)heap_caps_calloc(m_buffSizeRAM, sizeof(uint8_t), MALLOC_CAP_DEFAULT | MALLOC_CAP_INTERNAL);
        m_buffSize = m_buffSizeRAM - m_resBuffSizeRAM;
    }
    if(!m_buffer) return 0;
    m_f_init = true;
    resetBuffer();
    return m_buffSize;
}

where m_buffSize is actually 655350 (I checked it out at runtime).
I slightly changed the code as follow:

if(psramInit() && m_buffSizePSRAM > 0) { // PSRAM found, AudioBuffer will be allocated in PSRAM
    m_f_psram = true;
    m_buffSize = m_buffSizePSRAM;
    log_i("Available PSRAM: %lu bytes", (long unsigned int)ESP.getFreePsram());
    m_buffer = (uint8_t*)ps_calloc(m_buffSize, sizeof(uint8_t));
    log_i("Available PSRAM: %lu bytes %p", (long unsigned int)ESP.getFreePsram(), m_buffer);
    m_buffSize = m_buffSizePSRAM - m_resBuffSizePSRAM;
}

and this is the output:

[   343][I][Audio.cpp:43] init(): Available PSRAM: 2040835 bytes
[   351][I][Audio.cpp:45] init(): Available PSRAM: 0 bytes 0x3f80dbfc

I also tried to use malloc instead of calloc so the allocated area is not zero-ed. In that case it returns the correct available size, but of course the code won’t work anymore. If I zero the memory after:

m_buffer = (uint8_t*)ps_malloc(m_buffSize);
memset(m_buffer, 0, m_buffSize);
log_i("Available PSRAM: %lu bytes, %p", (long unsigned int)ESP.getFreePsram(), m_buffer);

it comes back to the previous behavior:

[   351][I][Audio.cpp:45] init(): Available PSRAM: 0 bytes 0x3f80dbfc

My development environment is:

• Ubuntu 24.10
• Visual Studio Code 1.95.3
• PlatformIO 6.1.16
• Espressif 32 (6.9.0)
• Hardware: DFRobot Firebeetle 2 ESP32-E N16R2
• Compiler: toolchain-xtensa-esp32 8.4.0

What can cause such an odd behavior?

Here my complete test code:

#include <Arduino.h>
#include <FS.h>
#include <SD.h>
#include <SPI.h>

#include "Audio.h"

#define PIN_SPI_SCK 18
#define PIN_SPI_MISO 19
#define PIN_SPI_MOSI 23
#define PIN_SD_CS 2

#define PIN_I2S_BCLK 25
#define PIN_I2S_LRC 26
#define PIN_I2S_DOUT 9

Audio audio;

void audio_process_i2s(int16_t *outBuff, uint16_t validSamples, uint8_t bitsPerSample, uint8_t channels, bool *continueI2S)
{
  log_i("%d", validSamples);
  *continueI2S = false;
}

void audio_info(const char *info)
{
    log_i("%s", info);
}

void setup()
{
  Serial.begin(115200);
  while (!Serial);

  uint32_t flashSize = ESP.getFlashChipSize();
  Serial.printf("Flash Size: %u bytesn", flashSize);
  uint32_t psramSize = ESP.getPsramSize();
  Serial.printf("PSRAM Size: %u bytesn", psramSize);
  uint32_t freeMemory = ESP.getFreeHeap();
  Serial.printf("Free Memory: %u bytesn", freeMemory);
  uint32_t Totalheap = ESP.getHeapSize();
  Serial.printf("Total heap: %u bytesn", Totalheap);
  uint32_t FreePSRAM = ESP.getFreePsram();
  Serial.printf("Free PSRAM: %u bytesn", FreePSRAM);

  SPI.setFrequency(1000000);
  SPI.begin(PIN_SPI_SCK, PIN_SPI_MISO, PIN_SPI_MOSI, PIN_SD_CS);
  if (SD.begin(PIN_SD_CS)) Serial.println("SD card mounted!");
  else Serial.println("Failed to mount SD card");

  File root = SD.open("/");
  audio.setPinout(PIN_I2S_BCLK, PIN_I2S_LRC, PIN_I2S_DOUT);
  audio.setVolume(15); 
  audio.connecttoFS(SD, "songs/bach.mp3");
}

void loop()
{
  audio.loop();
  vTaskDelay(1);
}