RPC over HDLC example project¶
The pw_hdlc module includes an example of bringing up a
pw_rpc server that can be used to invoke RPCs. The example code
is located at
pw_hdlc/rpc_example. This section walks through invoking RPCs
interactively and with a script using the RPC over HDLC example.
These instructions assume the STM32F429i Discovery board, but they work with any target with pw::sys_io implemented.
Getting started guide¶
1. Set up your board¶
Connect the board you’ll be communicating with. For the Discovery board, connect
the mini USB port, and note which serial device it appears as (e.g.
2. Build Pigweed¶
Activate the Pigweed environment and run the default build.
source activate.sh gn gen out ninja -C out
3. Flash the firmware image¶
After a successful build, the binary for the example will be located at
Flash this image to your board. If you are using the STM32F429i Discovery Board, you can flash the image with OpenOCD.
openocd -f targets/stm32f429i_disc1/py/stm32f429i_disc1_utils/openocd_stm32f4xx.cfg \ -c "program out/stm32f429i_disc1_debug/obj/pw_hdlc/rpc_example/bin/rpc_example.elf"
4. Invoke RPCs from in an interactive console¶
The RPC console uses IPython to make a rich interactive
console for working with pw_rpc. Run the RPC console with the following command,
/dev/ttyACM0 with the correct serial device for your board.
$ python -m pw_hdlc.rpc_console --device /dev/ttyACM0 Console for interacting with pw_rpc over HDLC. To start the console, provide a serial port as the --device argument and paths or globs for .proto files that define the RPC services to support: python -m pw_hdlc.rpc_console --device /dev/ttyUSB0 sample.proto This starts an IPython console for communicating with the connected device. A few variables are predefined in the interactive console. These include: rpcs - used to invoke RPCs device - the serial device used for communication client - the pw_rpc.Client An example echo RPC command: rpcs.pw.rpc.EchoService.Echo(msg="hello!") In :
RPCs may be accessed through the predefined
rpcs variable. RPCs are
organized by their protocol buffer package and RPC service, as defined in a
.proto file. To call the
Echo method is part of the
is in the
pw.rpc package. To invoke it synchronously, call
In : rpcs.pw.rpc.EchoService.Echo(msg="Your message here!") Out: (<Status.OK: 0>, msg: "Your message here!")
5. Invoke RPCs with a script¶
RPCs may also be invoked from Python scripts. Close the RPC console if it is running, and execute the example script. Set the –device argument to the serial port for your device.
$ pw_hdlc/rpc_example/example_script.py --device /dev/ttyACM0 The status was Status.OK The payload was msg: "Hello" The device says: Goodbye!
Local RPC example project¶
This example is similar to the above example, except it use socket to connect server and client running on the host.
1. Build Pigweed¶
Activate the Pigweed environment and build the code.
source activate.sh gn gen out pw watch
2. Start client side and server side¶
Run pw_rpc client (i.e. use echo.proto)
python -m pw_hdlc.rpc_console path/to/echo.proto -s localhost:33000
Run pw_rpc server
Then you can invoke RPCs from the interactive console on the client side.