esp-idf/examples/system/ipc/ipc_isr/riscv/README.md

Supported Targets	ESP32P4

IPC ISR Example

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). Unlike ESP32 or ESP32S3, for this chip, the callback function can be written in C.

The first callback get_mstatus_other_cpu() demonstrates a callback that simply returns the MSTATUS register of other core.

The second callback extended_ipc_isr_func() demonstrates how to return multiple values from the callback. The callback's void *arg points to a structure that contains the following:

• uint32_t in[]; that gives the callback multiple input arguments
• uint32_t out[]; that gives the callback multiple output arguments

The extended_ipc_isr_func() callback uses the in[] arguments does some work and then writes to out[].

How to use example

Hardware Required

Example should be able to run on any commonly available ESP32P4 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 for full steps to configure and use ESP-IDF to build projects.

Example output

I (411) example: Start
I (421) example: call get_mstatus_other_cpu
I (421) example: MSTATUS = 0x3880
I (421) example: call extended_ipc_isr_func
I (431) example: in[0] = 0x1
I (431) example: in[1] = 0x2
I (441) example: in[2] = 0x3
I (441) example: out[0] = (in[0] | in[1] | in[2]) = 0x3
I (451) example: out[1] = (in[0] + in[1] + in[2]) = 0x6
I (451) example: out[2] = MCAUSE of other cpu = 0xb800002c
I (461) example: out[3] = MSTATUS of other cpu = 0x3880
I (461) example: End