pw_hdlc#
Simple, robust, and efficient serial communication
Stable Python C++17 TypeScript Code Size Impact: 1400 to 2600 bytes
Simple: Transmit RPCs and other data between devices over serial
Robust: Detect corruption and data loss
Efficient: Stream to transport without buffering
pw_hdlc implements a subset of the High-Level Data Link Control (HDLC) protocol.
HDLC is a data link layer protocol intended for serial communication between
devices and is standardized as ISO/IEC 13239:2002.
Encoding looks like this:
// Writes a span of data to a pw::stream::Writer and returns the status. This
// implementation uses the pw_checksum module to compute the CRC-32 frame check
// sequence.
#include "pw_hdlc/encoder.h"
#include "pw_hdlc/sys_io_stream.h"
int main() {
pw::stream::SysIoWriter serial_writer;
Status status = pw::hdlc::WriteUIFrame(123 /* address */, data, serial_writer);
if (!status.ok()) {
PW_LOG_INFO("Writing frame failed! %s", status.str());
}
}
# Read bytes from serial and encode HDLC frames
import serial
from pw_hdlc import encode
ser = serial.Serial()
address = 123
ser.write(encode.ui_frame(address, b'your data here!'))
And decoding looks like this:
// Read individual bytes from pw::sys_io and decode HDLC frames.
#include "pw_hdlc/decoder.h"
#include "pw_sys_io/sys_io.h"
int main() {
std::byte data;
std::array<std::byte, 128> decode_buffer;
pw::hdlc::Decoder decoder(decode_buffer);
while (true) {
if (!pw::sys_io::ReadByte(&data).ok()) {
// Log serial reading error
}
Result<Frame> decoded_frame = decoder.Process(data);
if (decoded_frame.ok()) {
// Handle the decoded frame
}
}
}
# Decode data read from serial
import serial
from pw_hdlc import decode
ser = serial.Serial()
decoder = decode.FrameDecoder()
while True:
for frame in decoder.process_valid_frames(ser.read()):
# Handle the decoded frame