main.c

#include <stdio.h>

#include <rcl/rcl.h>
#include <rcl/error_handling.h>
#include <rclc/rclc.h>
#include <rclc/executor.h>
#include <std_msgs/msg/int32.h>
#include <rmw_microros/rmw_microros.h>

#include "pico/stdlib.h"
#include "pico_uart_transports.h"

#define RCCHECK(fn) { rcl_ret_t temp_rc = fn; if((temp_rc != RCL_RET_OK)){printf("Failed status on line %d: %d. Aborting.\n",__LINE__,(int)temp_rc); return 1;}}
#define RCSOFTCHECK(fn) { rcl_ret_t temp_rc = fn; if((temp_rc != RCL_RET_OK)){printf("Failed status on line %d: %d. Continuing.\n",__LINE__,(int)temp_rc);}}
#define LED_PIN 25

rcl_publisher_t publisher;
rcl_subscription_t subscriber;
std_msgs__msg__Int32 send_msg;
std_msgs__msg__Int32 recv_msg;

void timer_callback(rcl_timer_t * timer, int64_t last_call_time)
{
	(void) last_call_time;
	if (timer != NULL) {
		RCSOFTCHECK(rcl_publish(&publisher, &send_msg, NULL));
		printf("Sent: %d\n", send_msg.data);
		send_msg.data++;
	}
}

void subscription_callback(const void * msgin)
{
	const std_msgs__msg__Int32 * msg = (const std_msgs__msg__Int32 *)msgin;
	printf("Received: %d\n", msg->data);
}

int main(int argc, const char * const * argv)
{
	rmw_uros_set_custom_transport(
		true,
		NULL,
		pico_serial_transport_open,
		pico_serial_transport_close,
		pico_serial_transport_write,
		pico_serial_transport_read
	);

	gpio_init(LED_PIN);
    gpio_set_dir(LED_PIN, GPIO_OUT);

  	rcl_allocator_t allocator = rcl_get_default_allocator();
	rclc_support_t support;

	// create init_options
	RCCHECK(rclc_support_init(&support, 0, NULL, &allocator));

	// create node
	rcl_node_t node;
	RCCHECK(rclc_node_init_default(&node, "int32_publisher_subscriber_rclc", "", &support));

	// create publisher
	RCCHECK(rclc_publisher_init_default(
		&publisher,
		&node,
		ROSIDL_GET_MSG_TYPE_SUPPORT(std_msgs, msg, Int32),
		"int32_publisher"));

  	// create subscriber
	RCCHECK(rclc_subscription_init_default(
		&subscriber,
		&node,
		ROSIDL_GET_MSG_TYPE_SUPPORT(std_msgs, msg, Int32),
		"int32_subscriber"));

	// create timer,
	rcl_timer_t timer;
	const unsigned int timer_timeout = 1000;
	RCCHECK(rclc_timer_init_default(
		&timer,
		&support,
		RCL_MS_TO_NS(timer_timeout),
		timer_callback));

	// create executor
	rclc_executor_t executor = rclc_executor_get_zero_initialized_executor();
	RCCHECK(rclc_executor_init(&executor, &support.context, 2, &allocator));
	RCCHECK(rclc_executor_add_timer(&executor, &timer));
	RCCHECK(rclc_executor_add_subscription(&executor, &subscriber, &recv_msg, &subscription_callback, ON_NEW_DATA));

	send_msg.data = 0;

	gpio_put(LED_PIN, 1);
	
  	rclc_executor_spin(&executor);

	RCCHECK(rcl_subscription_fini(&subscriber, &node));
	RCCHECK(rcl_publisher_fini(&publisher, &node));
	RCCHECK(rcl_node_fini(&node));
}