How to use a Global Struct Array in psram esp32-wrover

PlatformIO IDE
1

I’m not sure if this is possible to do, but someone may know a solution.

I have a structured array:

struct Plot
  {
    float lng, lat;
  };
struct Plot roundplot[50000];

But this is too big for the internal memory.
So I was hoping to put this array in the PSRAM.

But this needs to be global so I can call a function and others that can access it like this for example:

void my_function()
{
  roundplot[roundplotIndex] = {longitude, latitude};
  roundplotIndex++;
}

I have seen this;

But I can’t get it working.

I’m using v1.0.6 and my “platformio.ini” is…

[env:esp-wrover-kit]
platform = espressif32@3.4.0
board = esp-wrover-kit
framework = arduino
build_flags = 
	-D_BSD_SOURCE
	-DBOARD_HAS_PSRAM
	-mfix-esp32-psram-cache-issue
upload_speed = 1500000
monitor_speed = 921600
lib_deps = 
	vshymanskyy/TinyGSM@^0.11.5
	knolleary/PubSubClient@^2.8
	bblanchon/ArduinoJson@^6.19.4
	adafruit/Adafruit GFX Library@^1.11.3
	adafruit/Adafruit SSD1306@^2.5.6

I assume I have to change some settings in a config file somewhere?

Any help would be appreciated.

1 Like
2

Well first of all, is PSRAM generally detected initialized correctly? Run a simple

#include <Arduino.h>

void setup() {
  log_d("Total heap: %d", ESP.getHeapSize());
  log_d("Free heap: %d", ESP.getFreeHeap());
  log_d("Total PSRAM: %d", ESP.getPsramSize());
  log_d("Free PSRAM: %d", ESP.getFreePsram());
}

void loop() {}

what does it output?

1 Like
3

Yes, I have this (I’m using flash FFS too):

FFS available memory:        1378241 bytes
FFS memory used:                9789 bytes
PSRAM size:                  4194252 bytes
PSRAM available memory:      4194252 bytes

I get this if I do this in setup():

Plot *roundplot = (Plot *)ps_malloc(128000 * sizeof(Plot));
Serial.printf("PSRAM available memory:     %8d bytes\n", ESP.getFreePsram());

PSRAM available memory:      3170236 bytes

So it looks like it’s allocating the psram memory usage.

4

Great, just change your global variable to be

struct Plot* roundplot;

in which you allocated then and it should be fine.

1 Like
5

Many thanks @maxgerhardt

I’ve stitched in the code as below to my project and is looking good, it compiles no errors or warnings and runs, the psram memory allocation looks correct too.

#include <Arduino.h>

struct Plot
{
  float lng, lat;
};
struct Plot* roundplot;

void setup() 
{
Serial.printf("PSRAM size:                 %8d bytes\n", ESP.getPsramSize());
Serial.printf("PSRAM available memory:     %8d bytes\n", ESP.getFreePsram());

roundplot = (Plot *)ps_malloc(128000 * sizeof(Plot));

Serial.printf("PSRAM available memory:     %8d bytes\n", ESP.getFreePsram());
}

void loop(){};
1 Like
6

Attribute to force static allocation in PSRAM is:

EXT_RAM_BSS_ATTR uint8_t Buffer[30000];

In IDF you have to enable a few SDK settings to get this to work. In Arduino the pre-compiled SDK does not have this enabled, you you have to use this:

__ attribute __((section(“.ext_ram.bss”))) uint8_t Buffer[30000]; // remove spaces around underline

Dynamic allocation in PSRAM is achieved by:

uint8_t *Buffer = nullptr;
Buffer = (uint8_t *) heap_caps_malloc(30000, MALLOC_CAP_8BIT | MALLOC_CAP_SPIRAM);

Alternatively, you can use:

ps_malloc // same as above, just cleaner + checks for PSRAM presence
ps_calloc // same as all above + initializes memory to zero

Verify where it is actually located:

printf(“Address: %p\n”, (void *)Buffer);

7

Can you name the settings please?
I would like to try this with pioarduino’s hybrid compile feature.

In Espressif32 Arduino a simple malloc > 4096 bytes will allocate from PSRAM automatically if PSRAM is available.

The threshold of 4096 bytes can be changed by calling heap_caps_malloc_extmem_enable(size_t limit);

1 Like
8

SDK setting is: CONFIG_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY

You are correct that malloc will automatically decide on the memory location, however sometimes user should be able to decide what to do. In my case I have a static 3kB array that is rarely used and in a non time critical code. I wanted to place it in PSRAM exclusively, so there is more space for fast operations in an integrated RAM.

9

Thank you for the reply!

I’m utlizing pioarduino’s hybrid compile feature which allows to change SDK config via the platformio.ini. But just changing CONFIG_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY=y leads to a crash on my ESP32-S3 DevKit C1 N16R8:

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x400570e8
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce2820,len:0x1188
load:0x403c8700,len:0x4
load:0x403c8704,len:0xbf0
load:0x403cb700,len:0x30e4
entry 0x403c88ac
Guru Meditation Error: Core  1 panic'ed (IllegalInstruction). Exception was unhandled.
Memory dump at 0x42006e0c: 08e0e666 03eb8000 89048d80
Core  1 register dump:
PC      : 0x42006e11  PS      : 0x00060034  A0      : 0x803768b4  A1      : 0x3fcec9e0  
A2      : 0x3fceca50  A3      : 0x00000000  A4      : 0x00000004  A5      : 0x3fc96eb0  
A6      : 0x00000001  A7      : 0x3fcec9ec  A8      : 0x00600000  A9      : 0x3fcec9c0  
A10     : 0x00000000  A11     : 0x3fc93cc0  A12     : 0x60020000  A13     : 0x00000002  
A14     : 0x7fffffff  A15     : 0x00000000  SAR     : 0x00000006  EXCCAUSE: 0x00000000  
EXCVADDR: 0x00000000  LBEG    : 0x400570e8  LEND    : 0x400570f3  LCOUNT  : 0xffffffff  


Backtrace: 0x42006e0e:0x3fcec9e0 0x403768b1:0x3fceca30 0x40378034:0x3fceca50 0x42006d7d:0x3fcecb10 0x403768b1:0x3fcecb60 0x40378034:0x3fcecb80 0x3ffffffd:0x3fcecc40 |<-CORRUPTED

[env:esp32s3]
platform = https://github.com/pioarduino/platform-espressif32/releases/download/53.03.13/platform-espressif32.zip
board = esp32-s3-devkitc-1
framework = arduino

board_build.arduino.memory_type = qio_opi
board_build.flash_mode = qio
board_build.psram_type = opi
board_upload.flash_size = 16MB
board_upload.maximum_size = 16777216
board_build.extra_flags = 
  -DBOARD_HAS_PSRAM

custom_sdkconfig = 
  CONFIG_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY=y

custom_component_remove =
    espressif/esp_hosted
    espressif/esp_wifi_remote
    espressif/esp-dsp
    espressif/esp32-camera
    espressif/libsodium
    espressif/esp-modbus
    espressif/qrcode
    espressif/esp_insights
    espressif/esp_diag_data_store
    espressif/esp_diagnostics
    espressif/esp_rainmaker
    espressif/rmaker_common

monitor_speed = 115200

#include <Arduino.h>

EXT_RAM_BSS_ATTR uint8_t buffer[4*1024*1024];

void setup() {
    Serial.begin(115200);
    Serial.printf("Free PSRAM: %d\r\n", ESP.getFreePsram());
    memset(buffer, 0, 4*1024*1024);
}

void loop() {}
10

Interesting. There must be something else behind, that causes crash.
I am using those lines of code without any issues on ESP32-S3:

__ attribute__((section(“.ext_ram.bss”))) uint8_t gBuffer[3000];
__ attribute__((section(“.ext_ram.bss”))) uint8_t GIFimage[100000]; // 100 kB, typ image is 50 kB

11

I’ll crosscheck this against an Arduino as ESP-IDF component project.

12

I don’t know why, but now it works :slight_smile:

Maybe I have forgotten a full clean in between my tests.

Using pioarduino’s platform-espressif32 with the settings shown in the platformio.ini above and
EXT_RAM_BSS_ATTR uint8_t buffer[4 * 1024 * 1024]; will reduce my available PSRAM by 4 MB as expected.

Nice to know - thanks again @aly-fly!

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