-`Resource Allocation <#cam-resource-allocation>`__ - covers how to allocate camera controller instances with properly set of configurations. It also covers how to recycle the resources when they are no longer needed.
A Camera Controller Driver can be implemented by the CSI peripheral, which requires the configuration that specified by :cpp:type:`esp_cam_ctlr_csi_config_t`.
If the configurations in :cpp:type:`esp_cam_ctlr_csi_config_t` is specified, users can call :cpp:func:`esp_cam_new_csi_ctlr` to allocate and initialize a CSI camera controller handle. This function will return an CSI camera controller handle if it runs correctly. You can take following code as reference.
If a previously installed Camera Controller Driver is no longer needed, it's recommended to recycle the resource by calling :cpp:func:`esp_cam_ctlr_del`, so that to release the underlying hardware.
Before starting camera controller operation, you need to enable the camera controller controller first, by calling :cpp:func:`esp_cam_ctlr_enable`. This function:
* Switches the driver state from **init** to **enable**.
..code:: c
ESP_ERROR_CHECK(esp_cam_ctlr_enable(handle));
Calling :cpp:func:`esp_cam_ctlr_disable` does the opposite, that is, put the driver back to the **init** state.
Before receiving camera signal from camera sensor, you need to start the Camera Controller Driver first, by calling :cpp:func:`esp_cam_ctlr_start`. This function:
After the Camera Controller Driver starts receiving, it can generate a specific event dynamically. If you have some functions that should be called when the event happens, please hook your function to the interrupt service routine by calling :cpp:func:`esp_cam_ctlr_register_event_callbacks`. All supported event callbacks are listed in :cpp:type:`esp_cam_ctlr_evt_cbs_t`:
-:cpp:member:`esp_cam_ctlr_evt_cbs_t::on_get_new_trans` sets a callback function when the Camera Controller Driver gets a new transaction which is passed from :cpp:func:`esp_cam_ctlr_receive`. As this function is called within the ISR context, you must ensure that the function does not attempt to block (e.g., by making sure that only FreeRTOS APIs with ``ISR`` suffix are called from within the function).
-:cpp:member:`esp_cam_ctlr_evt_cbs_t::on_trans_finished` sets a callback function when the Camera Controller Driver finishes a transaction. As this function is called within the ISR context, you must ensure that the function does not attempt to block (e.g., by making sure that only FreeRTOS APIs with ``ISR`` suffix are called from within the function).
The factory function :cpp:func:`esp_cam_new_csi_ctlr` and :cpp:func:`esp_cam_ctlr_del` are guaranteed to be thread safe by the driver, which means, user can call them from different RTOS tasks without protection by extra locks.
-:ref:`CONFIG_MIPI_CSI_ISR_IRAM_SAFE` controls whether the default ISR handler should be masked when the cache is disabled
.._cam-iram-safe:
IRAM Safe
^^^^^^^^^
By default, the CSI interrupt will be deferred when the cache is disabled because of writing or erasing the flash.
There is a Kconfig option :ref:`CONFIG_MIPI_CSI_ISR_IRAM_SAFE` that:
- Enables the interrupt being serviced even when the cache is disabled
- Places all functions that used by the ISR into IRAM
- Places driver object into DRAM (in case it is mapped to PSRAM by accident)
This allows the interrupt to run while the cache is disabled, but comes at the cost of increased IRAM consumption. So user callbacks need to notice that the code and data inside (the callback) should be IRAM-safe or DRAM-safe, when cache is disabled.
