Add 0x0d_timer_cbm: bare-metal TIMER0 repeating alarm driver for RP2350

drivers/0x0d_timer_cbm/Src/main.c

@@ -0,0 +1,51 @@
+/**
+  ******************************************************************************
+  * @file    main.c
+  * @author  Kevin Thomas
+  * @brief   Repeating timer alarm demonstration.
+  *
+  *          Configures TIMER0 alarm 0 to fire a callback every 1 second.
+  *          The callback prints "Timer heartbeat" over UART. The main
+  *          loop idles with WFI.
+  *
+  *          Wiring:
+  *            GPIO0 -> UART TX (USB-to-UART adapter RX)
+  *            GPIO1 -> UART RX (USB-to-UART adapter TX)
+  *            No external components required
+  *
+  ******************************************************************************
+  * @attention
+  *
+  * Copyright (c) 2026 Kevin Thomas.
+  * All rights reserved.
+  *
+  * This software is licensed under terms that can be found in the LICENSE file
+  * in the root directory of this software component.
+  * If no LICENSE file comes with this software, it is provided AS-IS.
+  *
+  ******************************************************************************
+  */
+
+#include "rp2350_timer.h"
+#include "rp2350_uart.h"
+
+/**
+  * @brief  Heartbeat callback invoked by TIMER0 alarm 0 IRQ.
+  * @retval None
+  */
+static void _heartbeat(void)
+{
+  uart_puts("Timer heartbeat\r\n");
+}
+
+/**
+  * @brief  Application entry point for the repeating timer demo.
+  * @retval int does not return
+  */
+int main(void)
+{
+  uart_puts("Timer alarm demo initialized\r\n");
+  timer_alarm_start(1000, _heartbeat);
+  while (1)
+    __asm__ volatile ("wfi");
+}