Port command protocol framework from E23x (RS485 data link)

Src/rs485.c

@@ -3,7 +3,6 @@
 #include "gd32f4xx_rcu.h"
 #include "gd32f4xx_gpio.h"
 #include "board_config.h"
-#include "uart.h"
 
 /* 独立接收环形缓冲区（与 debug 串口的 uart_ring_buffer 隔离），
    采用"预留一格"区分空/满，最大可用容量为 RS485_RX_BUFFER_SIZE-1 */
@@ -92,16 +91,11 @@ int rs485_rx_get(void) {
     return data;
 }
 
-void rs485_process(void) {
-    while (rs485_rx_available() > 0) {
-        int b = rs485_rx_get();
-        if (b < 0) {
-            break;
-        }
-        /* 拉通阶段：原样回发 RS485，同时转发 debug 串口便于观察 */
-        rs485_send((const uint8_t *)&b, 1);
-        debug_uart_write((uint8_t)b);
-    }
+void rs485_rx_clear(void) {
+    uint32_t primask = rs485_irq_save();
+    rs485_write_index = 0;
+    rs485_read_index = 0;
+    rs485_irq_restore(primask);
 }
 
 void rs485_irq_handler(void) {