eRPC

eRPC

About

eRPC (Embedded RPC) is an open source Remote Procedure Call (RPC) system for multichip embedded systems and heterogeneous multicore SoCs.

Unlike other modern RPC systems, such as the excellent Apache Thrift, eRPC distinguishes itself by being designed for tightly coupled systems, using plain C for remote functions, and having a small code size (<5kB). It is not intended for high performance distributed systems over a network.

eRPC does not force upon you any particular API style. It allows you to export existing C functions, without having to change their prototypes. (There are limits, of course.) And although the internal infrastructure is written in C++, most users will be able to use only the simple C setup APIs shown in the examples below.

A code generator tool called erpcgen is included. It accepts input IDL files, having an .erpc extension, that have definitions of your data types and remote interfaces, and generates the shim code that handles serialization and invocation. erpcgen can generate either C/C++ or Python code.

Example .erpc file:

// Define a data type.
enum LEDName { kRed, kGreen, kBlue }

// An interface is a logical grouping of functions.
interface IO {
    // Simple function declaration with an empty reply.
    set_led(LEDName whichLed, bool onOrOff) -> void
}

Client side usage:

void example_client(void) {
    // Initialize client running over UART.
    erpc_client_init(
        erpc_transport_cmsis_uart_init(Driver_USART0),
        erpc_mbf_dynamic_init());

    // Now we can call the remote function to turn on the green LED.
    set_led(kGreen, true);
}

Server side usage:

// Implement the remote function.
void set_led(LEDName whichLed, bool onOrOff) {
    // implementation goes here
}

void example_server(void) {
    // Initialize server running over UART.
    erpc_server_init(
        erpc_transport_cmsis_uart_init(Driver_USART0),
        erpc_mbf_dynamic_init());

    // Add the IO service.
    erpc_add_service_to_server(create_IO_service());

    // Run the server.
    erpc_server_run();
}

A number of transports are supported, and new transport classes are easy to write.

Supported transports:

CMSIS UART
NXP Kinetis SPI and DSPI
POSIX and Windows serial port
TCP/IP (mostly for testing)
NXP RPMsg-Lite / RPMsg TTY
SPIdev Linux
USB CDC
NXP Messaging Unit

eRPC is available with an unrestrictive BSD 3-clause license. See the LICENSE file for the full license text.

Releases

eRPC releases

Edge releases

Edge releases can by found on eRPC CircleCI webpage. Choose build of interest, then platform target and choose ARTIFACTS tab. Here you can find binary application from chosen build.

Documentation

Documentation is in the wiki section.

eRPC Infrastructure documentation

Examples

Example IDL is available in the examples/ folder.

Plenty of eRPC multicore and multiprocessor examples can be also found in NXP MCUXpressoSDK packages. Visit https://mcuxpresso.nxp.com to configure, build and download these packages.

To get the board list with multicore support (eRPC included) use filtering based on Middleware and search for 'multicore' string. Once the selected package with the multicore middleware is downloaded, see

<MCUXpressoSDK_install_dir>/boards/<board_name>/multicore_examples for eRPC multicore examples (RPMsg_Lite or Messaging Unit transports used) or

<MCUXpressoSDK_install_dir>/boards/<board_name>/multiprocessor_examples for eRPC multiprocessor examples (UART or SPI transports used).

eRPC examples use the 'erpc_' name prefix.

Another way of getting NXP MCUXpressoSDK eRPC multicore and multiprocessor examples is using the mcux-sdk Github repo. Follow the description how to use the West tool to clone and update the mcuxsdk repo in readme Overview section. Once done the armgcc eRPC examples can be found in

mcuxsdk/examples/<board_name>/multicore_examples or in

mcuxsdk/examples/<board_name>/multiprocessor_examples folders.

You can use the evkmimxrt1170 as the board_name for instance. Similar to MCUXpressoSDK packages the eRPC examples use the 'erpc_' name prefix.

References

This section provides links to interesting erpc-based projects, articles, blogs or guides:

Directories

doc - Documentation.

doxygen - Configuration and support files for running Doxygen over the eRPC C++ infrastructure and erpcgen code.

erpc_c - Holds C/C++ infrastructure for eRPC. This is the code you will include in your application.

erpc_python - Holds Python version of the eRPC infrastructure.

erpcgen - Holds source code for erpcgen and makefiles or project files to build erpcgen on Windows, Linux, and OS X.

erpcsniffer - Holds source code for erpcsniffer application.

examples - Several example IDL files.

mk - Contains common makefiles for building eRPC components.

test - Client/server tests. These tests verify the entire communications path from client to server and back.

utilities - Holds utilities which bring additional benefit to eRPC apps developers.

Building and installing

These build instructions apply to host PCs and embedded Linux. For bare metal or RTOS embedded environments, you should copy the erpc_c directory into your application sources.

The primary build system is makefile based. It builds a static library of the eRPC C/C++ infrastructure, the erpcgen executable, and optionally the unit tests.

The makefiles are compatible with gcc or clang on Linux, OS X, and Cygwin. A Windows build of erpcgen using Visual Studio is also available in the erpcgen/VisualStudio_v14/ directory. There is also an Xcode project file in the erpcgen/ directory which can be used to build erpcgen for OS X.

Requirements

Windows

Steps are described in erpcgen/VisualStudio_v14/readme_erpcgen.txt.

Linux and Cygwin

Install these packages:

bison: GNU yacc-compatible parser generator
flex: A fast lexical analyzer generator
make: the GNU version of the 'make' utility
python: Python language interpreter 3.6+ work
gcc-7: GNU C compiler (recommended version)
g++-7: GNU C++ compiler (recommended version)

Mandatory for case, when build for different architecture is needed

gcc-multilib, g++-multilib

Mac OS X

Install these packages with homebrew:

bison: GNU yacc-compatible parser generator (version 3.7.3 is recommended)
flex: A fast lexical analyzer generator (version 2.6.4 is recommended)

Building

To build the library and erpcgen, run from the repo root directory:

make

To install the library, erpcgen, and include files, run:

make install

You may need to sudo the make install.

By default this will install into /usr/local. If you want to install elsewhere, set the PREFIX environment variable. Example for installing into /opt:

make install PREFIX=/opt

List of top level Makefile targets:

erpc: build the liberpc.a static library
erpcgen: build the erpcgen tool
test: build the unit tests under the test/ directory
all: build all of the above
install: install liberpc.a, erpcgen, and include files

eRPC code is validated with respect to the C++ 11 standard.

Installing for Python

To install the Python infrastructure for eRPC see instructions in the erpc_python folder readme.

Known issues and limitations

Static allocations controlled by the ERPC_ALLOCATION_POLICY config macro are not fully supported yet, i.e. not all erpc objects can be allocated statically now. It deals with the ongoing process and the full static allocations support will be added in the future.

Code providing

Repository on Github contains two main branches. Master and develop. Code is developed on develop branch. Release version is created via merging develop branch into master branch.

EmbeddedRPC/erpc

EmbeddedRPC

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