ESP32 SDCARD speed issue - esp32

Question

I am trying to use SD Card on Wrover kit but it seems that speed is the big issue on the board itself.
At first I wanted to download file from the net and save it to SDCARD but it took too long so to test it I've written a loop to save some chars into file and create ~1MB large file on a SDCARD and it takes forever.
What could be the cause that ~1MB file could be such a long task to do.
I have combined two examples into one to do the task.
Also I have commented everything and left just part with writing to file to demonstrate issue.
/* ESP HTTP Client Example
This example code is in the Public Domain (or CC0 licensed, at your option.)
Unless required by applicable law or agreed to in writing, this
software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied.
*/
#define LOG_LOCAL_LEVEL ESP_LOG_ERROR
#include <string.h>
#include <stdlib.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "esp_system.h"
#include "nvs_flash.h"
#include "app_wifi.h"
#include "esp_http_client.h"
/* SD CARD */
#include "esp_vfs_fat.h"
#include "driver/sdmmc_host.h"
#include "driver/sdspi_host.h"
#include "sdmmc_cmd.h"
/* SD CARD */
#define USE_SPI_MODE
#ifdef USE_SPI_MODE
// Pin mapping when using SPI mode.
// With this mapping, SD card can be used both in SPI and 1-line SD mode.
// Note that a pull-up on CS line is required in SD mode.
#define PIN_NUM_MISO 2
#define PIN_NUM_MOSI 15
#define PIN_NUM_CLK 14
#define PIN_NUM_CS 13
#endif //USE_SPI_MODE
//#define MAX_HTTP_RECV_BUFFER 512
#define MAX_HTTP_RECV_BUFFER 1024
static const char *TAG = "HTTP_CLIENT";
// ------------------ GLOBAL VARS -----------------------------
FILE *fp=NULL;
// ------------------ GLOBAL VARS -----------------------------
/* Root cert for howsmyssl.com, taken from howsmyssl_com_root_cert.pem
The PEM file was extracted from the output of this command:
openssl s_client -showcerts -connect www.howsmyssl.com:443 </dev/null
The CA root cert is the last cert given in the chain of certs.
To embed it in the app binary, the PEM file is named
in the component.mk COMPONENT_EMBED_TXTFILES variable.
*/
extern const char howsmyssl_com_root_cert_pem_start[] asm("_binary_howsmyssl_com_root_cert_pem_start");
extern const char howsmyssl_com_root_cert_pem_end[] asm("_binary_howsmyssl_com_root_cert_pem_end");
esp_err_t _http_event_handler(esp_http_client_event_t *evt)
{
switch(evt->event_id) {
case HTTP_EVENT_ERROR:
ESP_LOGE (TAG, "HTTP_EVENT_ERROR");
break;
case HTTP_EVENT_ON_CONNECTED:
ESP_LOGE (TAG, "HTTP_EVENT_ON_CONNECTED");
break;
case HTTP_EVENT_HEADER_SENT:
ESP_LOGE (TAG, "HTTP_EVENT_HEADER_SENT");
break;
case HTTP_EVENT_ON_HEADER:
ESP_LOGE (TAG, "HTTP_EVENT_ON_HEADER, key=%s, value=%s", evt->header_key, evt->header_value);
break;
case HTTP_EVENT_ON_DATA:
ESP_LOGE (TAG, "HTTP_EVENT_ON_DATA, len=%d", evt->data_len);
if (!esp_http_client_is_chunked_response(evt->client)) {
// Write out data
// printf("%.*s", evt->data_len, (char*)evt->data);
if(fp == NULL){
fp = fopen("/sdcard/muzika.mp3","wb");
}
if(fp != NULL){
fwrite(evt->data,1,evt->data_len,fp);
ESP_LOGE (TAG, "---------- HTTP_EVENT_ON_DATA - WRITING TO SD CARD ----------");
}
}
break;
case HTTP_EVENT_ON_FINISH:
ESP_LOGE (TAG, "HTTP_EVENT_ON_FINISH");
fclose(fp);
fp = NULL;
break;
case HTTP_EVENT_DISCONNECTED:
ESP_LOGE (TAG, "HTTP_EVENT_DISCONNECTED");
break;
}
return ESP_OK;
}
static void http_download_chunk()
{
esp_http_client_config_t config = {
//.url = "http://httpbin.org/stream-bytes/8912",
.url = "http://www.theoctopusproject.com/mp3/whatthey.mp3",
.event_handler = _http_event_handler,
};
esp_http_client_handle_t client = esp_http_client_init(&config);
esp_err_t err = esp_http_client_perform(client);
if (err == ESP_OK) {
ESP_LOGI(TAG, "HTTP chunk encoding Status = %d, content_length = %d",
esp_http_client_get_status_code(client),
esp_http_client_get_content_length(client));
} else {
ESP_LOGE(TAG, "Error perform http request %s", esp_err_to_name(err));
}
esp_http_client_cleanup(client);
}
static void http_test_task(void *pvParameters)
{
app_wifi_wait_connected();
ESP_LOGI(TAG, "Connected to AP, begin http example");
http_download_chunk();
ESP_LOGI(TAG, "Finish http example");
vTaskDelete(NULL);
}
void app_main()
{
esp_err_t ret = nvs_flash_init();
if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
ESP_ERROR_CHECK(nvs_flash_erase());
ret = nvs_flash_init();
}
ESP_ERROR_CHECK(ret);
// -- app_wifi_initialise();
/* SDCARD SETUP */
#ifndef USE_SPI_MODE
ESP_LOGI(TAG, "Using SDMMC peripheral");
sdmmc_host_t host = SDMMC_HOST_DEFAULT();
// This initializes the slot without card detect (CD) and write protect (WP) signals.
// Modify slot_config.gpio_cd and slot_config.gpio_wp if your board has these signals.
sdmmc_slot_config_t slot_config = SDMMC_SLOT_CONFIG_DEFAULT();
// To use 1-line SD mode, uncomment the following line:
// slot_config.width = 1;
// GPIOs 15, 2, 4, 12, 13 should have external 10k pull-ups.
// Internal pull-ups are not sufficient. However, enabling internal pull-ups
// does make a difference some boards, so we do that here.
gpio_set_pull_mode(15, GPIO_PULLUP_ONLY); // CMD, needed in 4- and 1- line modes
gpio_set_pull_mode(2, GPIO_PULLUP_ONLY); // D0, needed in 4- and 1-line modes
gpio_set_pull_mode(4, GPIO_PULLUP_ONLY); // D1, needed in 4-line mode only
gpio_set_pull_mode(12, GPIO_PULLUP_ONLY); // D2, needed in 4-line mode only
gpio_set_pull_mode(13, GPIO_PULLUP_ONLY); // D3, needed in 4- and 1-line modes
#else
ESP_LOGI(TAG, "Using SPI peripheral");
sdmmc_host_t host = SDSPI_HOST_DEFAULT();
sdspi_slot_config_t slot_config = SDSPI_SLOT_CONFIG_DEFAULT();
slot_config.gpio_miso = PIN_NUM_MISO;
slot_config.gpio_mosi = PIN_NUM_MOSI;
slot_config.gpio_sck = PIN_NUM_CLK;
slot_config.gpio_cs = PIN_NUM_CS;
// This initializes the slot without card detect (CD) and write protect (WP) signals.
// Modify slot_config.gpio_cd and slot_config.gpio_wp if your board has these signals.
#endif //USE_SPI_MODE
// Options for mounting the filesystem.
// If format_if_mount_failed is set to true, SD card will be partitioned and
// formatted in case when mounting fails.
esp_vfs_fat_sdmmc_mount_config_t mount_config = {
.format_if_mount_failed = false,
.max_files = 5,
.allocation_unit_size = 16 * 1024
};
// Use settings defined above to initialize SD card and mount FAT filesystem.
// Note: esp_vfs_fat_sdmmc_mount is an all-in-one convenience function.
// Please check its source code and implement error recovery when developing
// production applications.
sdmmc_card_t* card;
ret = esp_vfs_fat_sdmmc_mount("/sdcard", &host, &slot_config, &mount_config, &card);
if (ret != ESP_OK) {
if (ret == ESP_FAIL) {
ESP_LOGE(TAG, "Failed to mount filesystem. "
"If you want the card to be formatted, set format_if_mount_failed = true.");
} else {
ESP_LOGE(TAG, "Failed to initialize the card (%s). "
"Make sure SD card lines have pull-up resistors in place.", esp_err_to_name(ret));
}
return;
}
// Card has been initialized, print its properties
sdmmc_card_print_info(stdout, card);
// Use POSIX and C standard library functions to work with files.
// First create a file.
ESP_LOGE(TAG, "Opening file");
FILE* f = fopen("/sdcard/hello.txt", "w");
if (f == NULL) {
ESP_LOGE(TAG, "Failed to open file for writing");
return;
}
// ------------------------ WRITE INTO FILE -------------------
int j=0;
for(int i = 0 ; i < 1048576 ; i++,j++){
//fprintf(f, "Hello %s!\n", card->cid.name);
fprintf(f, "X");
if(j > 1024){
vTaskDelay(3);
j = 0;
}
}
fclose(f);
ESP_LOGE(TAG, "File written");
// ------------------------ WRITE INTO FILE -------------------
//-- xTaskCreate(&http_test_task, "http_test_task", 8192, NULL, 5, NULL);
//xTaskCreate(&http_test_task, "http_test_task", 16384, NULL, 5, NULL);
}

Answer 1

Your example is writing one byte at a time. That won't get you an accurate idea of how the overall speed of writing to the SD card - your code will spend a disproportionate amount of time processing the individual writes.
If you want to get a more accurate idea of how fast you can write to the card, try writing 1024 bytes (or even more) at a time. Benchmarks that measure maximum throughput and performance-sensitive applications will always write as much data as they can at a time in order to minimize the overhead of the write.
Also, don't use fprintf() if possible. It has extra overhead because it parses the format string. Try fwrite() - it will have less overhead and will give you a better idea of what you can expect in the best case.
Try something like this instead:
char *buf = malloc(1024);
if(buf) {
for(int i = 0; i < 1024; i++) {
fwrite(buf, 1, 1024, f);
vTaskDelay(3); // you'll speed this up if you can omit this
}
ESP_LOGE(TAG, "File written");
free(buf);
} else
ESP_LOGE(TAG, "malloc() failed");
fclose(f);