feat: add PSRAM-DMA flag + runtime API for ESP32-S2/S3; remove 16MHz heuristic

Add a Kconfig switch (CONFIG_CAMERA_PSRAM_DMA) to enable camera to PSRAM
DMA copy on ESP32-S2 and ESP32-S3 targets, in favor of removing the
undocumented "set XCLK=16MHz to enable PSRAM DMA" heuristic.

cam_hal.c:
- Select psram_mode = true when CONFIG_CAMERA_PSRAM_DMA && target is S2/S3.
- Otherwise psram_mode = false.
- Log whether PSRAM DMA mode is enabled.

Kconfig:
- New bool CAMERA_PSRAM_DMA (default n) under Camera configuration.

Runtime control:
- New public API:
  - esp_camera_set_psram_mode(bool enable)
  - esp_camera_get_psram_mode(void)
  - esp_camera_reconfigure(const camera_config_t *cfg)

README/test:
- Remove stale 16MHz XCLK comments.
- Add short note describing CONFIG_CAMERA_PSRAM_DMA.

Author: RubenKelevra

Kconfig

@@ -214,6 +214,14 @@ menu "Camera configuration"
             Maximum value of DMA buffer
             Larger values may fail to allocate due to insufficient contiguous memory blocks, and smaller value may cause DMA interrupt to be too frequent.
 
+    config CAMERA_PSRAM_DMA
+        bool "Enable PSRAM DMA mode by default"
+        depends on IDF_TARGET_ESP32S2 || IDF_TARGET_ESP32S3
+        default n
+        help
+            Enable DMA transfers directly from PSRAM on supported targets
+            (ESP32-S2 and ESP32-S3) by default.
+
     choice CAMERA_JPEG_MODE_FRAME_SIZE_OPTION
         prompt "JPEG mode frame size option"
         default CAMERA_JPEG_MODE_FRAME_SIZE_AUTO

README.md

@@ -38,6 +38,8 @@ This repository hosts ESP32 series Soc compatible driver for image sensors. Addi
 - Using YUV or RGB puts a lot of strain on the chip because writing to PSRAM is not particularly fast. The result is that image data might be missing. This is particularly true if WiFi is enabled. If you need RGB data, it is recommended that JPEG is captured and then turned into RGB using `fmt2rgb888` or `fmt2bmp`/`frame2bmp`.
 - When 1 frame buffer is used, the driver will wait for the current frame to finish (VSYNC) and start I2S DMA. After the frame is acquired, I2S will be stopped and the frame buffer returned to the application. This approach gives more control over the system, but results in longer time to get the frame.
 - When 2 or more frame bufers are used, I2S is running in continuous mode and each frame is pushed to a queue that the application can access. This approach puts more strain on the CPU/Memory, but allows for double the frame rate. Please use only with JPEG.
+- The Kconfig option `CONFIG_CAMERA_PSRAM_DMA` enables PSRAM DMA mode on ESP32-S2 and ESP32-S3 devices. This flag defaults to false.
+- You can switch PSRAM DMA mode at runtime using `esp_camera_set_psram_mode()`.
 
 ## Installation Instructions
 
@@ -135,7 +137,7 @@ static camera_config_t camera_config = {
     .pin_href = CAM_PIN_HREF,
     .pin_pclk = CAM_PIN_PCLK,
 
-    .xclk_freq_hz = 20000000,//EXPERIMENTAL: Set to 16MHz on ESP32-S2 or ESP32-S3 to enable EDMA mode
+    .xclk_freq_hz = 20000000,
     .ledc_timer = LEDC_TIMER_0,
     .ledc_channel = LEDC_CHANNEL_0,
 

driver/cam_hal.c

@@ -16,6 +16,7 @@
 #include <string.h>
 #include <stdalign.h>
 #include "esp_heap_caps.h"
+#include "freertos/FreeRTOS.h"
 #include "ll_cam.h"
 #include "cam_hal.h"
 
@@ -41,6 +42,14 @@
 
 static const char *TAG = "cam_hal";
 static cam_obj_t *cam_obj = NULL;
+#if defined(CONFIG_CAMERA_PSRAM_DMA)
+#define CAMERA_PSRAM_DMA_ENABLED CONFIG_CAMERA_PSRAM_DMA
+#else
+#define CAMERA_PSRAM_DMA_ENABLED 0
+#endif
+
+static volatile bool g_psram_dma_mode = CAMERA_PSRAM_DMA_ENABLED;
+static portMUX_TYPE g_psram_dma_lock = portMUX_INITIALIZER_UNLOCKED;
 
 /* At top of cam_hal.c – one switch for noisy ISR prints */
 #ifndef CAM_LOG_SPAM_EVERY_FRAME
@@ -411,11 +420,12 @@ esp_err_t cam_config(const camera_config_t *config, framesize_t frame_size, uint
     CAM_CHECK_GOTO(ret == ESP_OK, "ll_cam_set_sample_mode failed", err);
 
     cam_obj->jpeg_mode = config->pixel_format == PIXFORMAT_JPEG;
-#if CONFIG_IDF_TARGET_ESP32
-    cam_obj->psram_mode = false;
+#if CONFIG_IDF_TARGET_ESP32S2 || CONFIG_IDF_TARGET_ESP32S3
+    cam_obj->psram_mode = g_psram_dma_mode;
 #else
-    cam_obj->psram_mode = (config->xclk_freq_hz == 16000000);
+    cam_obj->psram_mode = false;
 #endif
+    ESP_LOGI(TAG, "PSRAM DMA mode %s", cam_obj->psram_mode ? "enabled" : "disabled");
     cam_obj->frame_cnt = config->fb_count;
     cam_obj->width = resolution[frame_size].width;
     cam_obj->height = resolution[frame_size].height;
@@ -612,3 +622,15 @@ bool cam_get_available_frames(void)
 {
     return 0 < uxQueueMessagesWaiting(cam_obj->frame_buffer_queue);
 }
+
+void cam_set_psram_mode(bool enable)
+{
+    portENTER_CRITICAL(&g_psram_dma_lock);
+    g_psram_dma_mode = enable;
+    portEXIT_CRITICAL(&g_psram_dma_lock);
+}
+
+bool cam_get_psram_mode(void)
+{
+    return g_psram_dma_mode;
+}

driver/esp_camera.c

@@ -95,6 +95,7 @@ typedef struct {
 static const char *CAMERA_SENSOR_NVS_KEY = "sensor";
 static const char *CAMERA_PIXFORMAT_NVS_KEY = "pixformat";
 static camera_state_t *s_state = NULL;
+static camera_config_t s_saved_config;
 
 #if CONFIG_IDF_TARGET_ESP32S3 // LCD_CAM module of ESP32-S3 will generate xclk
 #define CAMERA_ENABLE_OUT_CLOCK(v)
@@ -298,6 +299,7 @@ static pixformat_t get_output_data_format(camera_conv_mode_t conv_mode)
 esp_err_t esp_camera_init(const camera_config_t *config)
 {
     esp_err_t err;
+    s_saved_config = *config;
     err = cam_init(config);
     if (err != ESP_OK) {
         ESP_LOGE(TAG, "Camera init failed with error 0x%x", err);
@@ -517,3 +519,32 @@ bool esp_camera_available_frames(void)
     }
     return cam_get_available_frames();
 }
+
+esp_err_t esp_camera_reconfigure(const camera_config_t *config)
+{
+    if (!config) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    if (s_state) {
+        esp_err_t err = esp_camera_deinit();
+        if (err != ESP_OK) {
+            return err;
+        }
+    }
+    s_saved_config = *config;
+    return esp_camera_init(&s_saved_config);
+}
+
+esp_err_t esp_camera_set_psram_mode(bool enable)
+{
+    cam_set_psram_mode(enable);
+    if (!s_state) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    return esp_camera_reconfigure(&s_saved_config);
+}
+
+bool esp_camera_get_psram_mode(void)
+{
+    return cam_get_psram_mode();
+}

driver/include/esp_camera.h

@@ -138,7 +138,7 @@ typedef struct {
     int pin_href;                   /*!< GPIO pin for camera HREF line */
     int pin_pclk;                   /*!< GPIO pin for camera PCLK line */
 
-    int xclk_freq_hz;               /*!< Frequency of XCLK signal, in Hz. EXPERIMENTAL: Set to 16MHz on ESP32-S2 or ESP32-S3 to enable EDMA mode */
+    int xclk_freq_hz;               /*!< Frequency of XCLK signal, in Hz. */
 
     ledc_timer_t ledc_timer;        /*!< LEDC timer to be used for generating XCLK  */
     ledc_channel_t ledc_channel;    /*!< LEDC channel to be used for generating XCLK  */
@@ -245,6 +245,35 @@ void esp_camera_return_all(void);
  */
 bool esp_camera_available_frames(void);
 
+/**
+ * @brief Enable or disable PSRAM DMA mode at runtime.
+ *
+ * @param enable  True to enable PSRAM DMA mode, false to disable it.
+ * @return
+ * - ESP_OK on success
+ * - ESP_ERR_INVALID_STATE if the camera is not initialized
+ * - Propagated error from reinitialization on failure
+ */
+esp_err_t esp_camera_set_psram_mode(bool enable);
+
+/**
+ * @brief Reinitialize the camera with a new configuration.
+ *
+ * @param config  Updated camera configuration structure
+ * @return
+ * - ESP_OK on success
+ * - ESP_ERR_INVALID_ARG if config is NULL
+ * - Propagated error from deinit or init if they fail
+ */
+esp_err_t esp_camera_reconfigure(const camera_config_t *config);
+
+/**
+ * @brief Get current PSRAM DMA mode state.
+ *
+ * @return True if PSRAM DMA is enabled, false otherwise.
+ */
+bool esp_camera_get_psram_mode(void);
+
 
 #ifdef __cplusplus
 }

driver/private_include/cam_hal.h

@@ -59,6 +59,9 @@ void cam_give_all(void);
 
 bool cam_get_available_frames(void);
 
+void cam_set_psram_mode(bool enable);
+bool cam_get_psram_mode(void);
+
 #ifdef __cplusplus
 }
 #endif

test/test_camera.c

@@ -144,7 +144,6 @@ static esp_err_t init_camera(uint32_t xclk_freq_hz, pixformat_t pixel_format, fr
         .pin_href = HREF_GPIO_NUM,
         .pin_pclk = PCLK_GPIO_NUM,
 
-        //EXPERIMENTAL: Set to 16MHz on ESP32-S2 or ESP32-S3 to enable EDMA mode
         .xclk_freq_hz = xclk_freq_hz,
         .ledc_timer = LEDC_TIMER_0,
         .ledc_channel = LEDC_CHANNEL_0,