This example demonstrates how to use the IPC ISR feature (which allows an IPC to run in the context of a High Priority Interrupt). The level of the IPC ISR interrupt depends on the `CONFIG_ESP_SYSTEM_CHECK_INT_LEVEL` option. The IPC ISR feature can be useful in cases where users need to quickly get the state of the other CPU (consult the [IPC documentation](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/ipc.html)). The `asm_funcs.S` file contains the callback that will be run on the other core. The callback should be fairly simple and must be entirely in assembly.
The second assembly callback `extended_ipc_isr_asm()` demonstrates a more complex callback that uses a buffer (provided as the callback's argument) to save some registers and return multiple values from the callback. The callback's `void *arg` points to a buffer containing the following:
-`uint32_t regs[];` that gives the callback an area to save some of the CPUs registers. Saving the registers gives the callback more scratch registers to use.
-`uint32_t in[];` that gives the callback multiple input arguments
-`uint32_t out[];` that gives the callback multiple output arguments
The `extended_ipc_isr_asm()` callback will simply save/restore registers to/from `regs[]`, then use the arguments passed by `in[]` to do some work, then write the results to `out[]`.
Example should be able to run on any commonly available ESP32 development board. The chip should have two cores.
### Configure the project
-`CONFIG_FREERTOS_UNICORE` - disabled,
-`CONFIG_ESP_IPC_ISR_ENABLE` - enabled.
```
idf.py menuconfig
```
### Build and Flash
```
idf.py build flash monitor
```
(To exit the serial monitor, type ``Ctrl-]``.)
See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
