Examples

Three examples share one bus definition, examples/config/baton_user_config.h (the Baton Inspector bus definition tools/baton_inspector/examples/example_bus.json describes the same bus): master 0x01, slaves 0x11 and 0x12, the state NODE_STATUS (uptime in seconds) and the events CMD_SET_OUTPUT and OUTPUT_REPORT.

Example	Role	Platform	Built and run in CI
Bare metal	Slave 0x11	Any MCU; runs on a PC against a simulated board	Yes, as a self-checking test
Host serial master	Master 0x01	Linux, macOS, Windows	Built
Zephyr	Slave 0x12	Any Zephyr board	No — needs a Zephyr workspace; not compiled in this repository

cmake --preset "BATON[Examples]"
cmake --build "build/BATON[Examples]"
ctest --test-dir "build/BATON[Examples]" -L example --output-on-failure

Bare metal

File	Content
examples/bare_metal/board.h	Four board functions: board_init(), board_millis(), board_uart_write(), board_idle(); the application provides app_uart_rx_isr()
examples/bare_metal/main.c	The slave: configuration, main loop, uptime state, output commands
examples/bare_metal/board_host.c	board.h on a PC: a simulated single-wire bus with the master and slave 0x12 as further Baton nodes; checks the results

Structure. The UART receive interrupt calls app_uart_rx_isr(), which passes the byte to baton_node_rx_isr(). The main loop calls baton_node_process() every millisecond, publishes NODE_STATUS once per second, and in on_message applies CMD_SET_OUTPUT and answers with an OUTPUT_REPORT event to the sender. Everything runs in the main loop, so no critical section is configured.

On a PC. board_idle() advances a simulated clock by 1 ms and moves one byte per transmitter over the bus; every byte reaches every node, the sender included (echo). Before each of the three requests a burst of line noise — a broken header A5 11 01 00 with an invalid length, and a stray byte — is put on the idle bus. Real output:

bare-metal example: slave 0x11 at 9600 bit/s on a simulated single-wire bus
  1502 ms  master -> 0x11  CMD_SET_OUTPUT output 0 = 0x01 (after line noise)
  1563 ms  master <- 0x11  OUTPUT_REPORT output 0 = 0x01
  2202 ms  0x12   -> 0x11  CMD_SET_OUTPUT output 1 = 0x55 (after line noise)
  2290 ms  0x12   <- 0x11  OUTPUT_REPORT output 1 = 0x55
  3106 ms  master -> 0x11  CMD_SET_OUTPUT output 2 = 0x00 (after line noise)
  3147 ms  master <- 0x11  OUTPUT_REPORT output 2 = 0x00
master: 274 polls (0 without answer), 3 CRC errors, 0 frames aborted by timeout
ok    master got 2 OUTPUT_REPORT events
ok    last report to the master: output 2 = 0x00
ok    slave 0x12 got 1 OUTPUT_REPORT event
ok    report to 0x12: output 1 = 0x55
ok    master sees the uptime state of 0x11
ok    slave 0x12 sees the uptime state of 0x11
ok    no collisions on the bus
EXAMPLE PASSED

The three CRC errors are the three noise bursts (their length byte is invalid).

Porting. Implement board.h for the MCU:

Function	Implementation
board_init()	Clock the UART, configure single-wire half duplex 8N1 at the baud rate, enable the RX interrupt (and the TX interrupt in the driver)
board_millis()	A 1 ms SysTick counter
board_uart_write()	Store the buffer and start an interrupt or DMA transmission; return 0
board_idle()	__WFI(); the SysTick interrupt wakes the loop every millisecond

Host serial master

File	Content
examples/host_serial/main.c	Command-line master baton_master
examples/host_serial/serial_port.h	Five functions: open, write, read with timeout, close, millisecond clock
examples/host_serial/serial_port_posix.c	termios implementation (Linux, macOS)
examples/host_serial/serial_port_win32.c	Win32 implementation

baton_master <port> [--baud N] [--echo] [--seconds N] [--set ADDR OUTPUT VALUE]...
baton_master /dev/ttyUSB0 --set 0x11 0 1
baton_master COM3 --echo --seconds 30

The master polls 0x11 and 0x12, prints every message it receives and, once per second, the number of polls, the answered ones and the CRC errors. Each --set queues a CMD_SET_OUTPUT event. Use --echo with a single-wire adapter that receives its own bytes; without it, the end of serial_write() is taken as the end of the transmission (baton_node_tx_done_isr()). The example has not been run against hardware yet; without an adapter it reports cannot open <port>.

Zephyr

File	Content
examples/zephyr/src/main.c	Slave 0x12: UART interrupt driver, one protocol thread
examples/zephyr/CMakeLists.txt	Includes baton.cmake, links zephyr_interface
examples/zephyr/prj.conf	Serial, interrupt-driven UART, no heap
examples/zephyr/app.overlay.example	The chosen node baton,uart

west build -b <board> examples/zephyr -- -DDTC_OVERLAY_FILE=<board>.overlay

The UART interrupt passes received bytes to baton_node_rx_isr() and feeds the transmit FIFO from the buffer of the write function; the transmission ends with the echo of the last byte (rx_echo). A thread calls baton_node_process() every millisecond and publishes the uptime. enter_critical and exit_critical use irq_lock() so that other threads may send events. Disable the console and logging on the bus UART.

This example is not compiled in this repository (no Zephyr workspace in CI); treat it as a starting point.