Quick start

This page assumes you have completed the installation and can run make TARGET=host. We will build the examples and run a few of them on the host — no hardware required.

The same code, everywhere

A Lapilli application includes one header, hal/hal.h, and calls only lpl_* symbols. This blinks an LED:

#include "hal.h"

int main(void) {
    lpl_system_init();
    lpl_gpio_init(LPL_PIN_A0, LPL_GPIO_OUTPUT);

    while (1) {
        lpl_gpio_toggle(LPL_PIN_A0);
        lpl_timer_delay_ms(500);
    }
}

On an STM32L452RE this toggles a physical pin. On the host it prints GPIO state changes to stderr. There is no #ifdef, no platform check — the build system selects the port.

Build and run the examples

Build the library and every example for the host:
Terminal window
```
make TARGET=host examples
```
Run blinky — it prints GPIO state changes to stderr:
Terminal window
```
./build/host/examples/blinky/blinky
```
Run uart_echo — two processes talking over a Unix named pipe, exactly like two boards wired via UART:
Terminal window
```
./build/host/examples/uart_echo/node_b &
./build/host/examples/uart_echo/node_a
```

Each example also has its own Makefile and can be built standalone from its own directory:

make -C examples/blinky TARGET=host ROOT=$(pwd)

Run the test suite

make TARGET=host test

The HAL tests run as ordinary host processes. The POSIX port is the primary CI target — hardware is never a prerequisite for a green build.

Cross-compile for STM32

If you installed arm-none-eabi-gcc, the very same examples cross-compile to a flashable binary:

make TARGET=stm32l4 examples
# → build/stm32l4/examples/blinky/blinky.bin  (ready to flash)

Next steps

See it live

The dashboard visualizes GPIO, UART, ADC, and the simulation bus in real time — and lets you inject signals back into the running firmware.