diff --git a/example/boot2/main.c b/example/boot2/main.c
index 15e81ad..99ac330 100644
--- a/example/boot2/main.c
+++ b/example/boot2/main.c
@@ -76,6 +76,81 @@ struct uart_cfg_s uart_cfg = {
     .rx_fifo_level = UART_FIFO_LEVEL_1_2,
 };
 
+void uart_process(uint16_t code, uint16_t length)
+{
+    uint8_t *p;
+    uint32_t checksum_read, checksum_calc;
+    uint16_t i;
+    uint32_t v1, v2;
+    
+    p = uart_rx_buffer + 8;
+    if ((length > 0) && (length <= 4)) {
+        return;
+    }
+    if (length > 4) {
+        checksum_read = ((uint32_t)p[0] << 24) | ((uint32_t)p[1] << 16) | ((uint32_t)p[2] << 8) | ((uint32_t)p[3] << 0);
+        p += 4;
+        length -= 4;
+        checksum_calc = 0;
+        for (i = 0; i < length; i++) {
+            checksum_calc += p[i];
+        }
+        if (checksum_read != checksum_calc) {
+            return;
+        }
+    }
+
+    if (code == 0x0001) {
+        v1 = ((uint32_t)p[0] << 24) | ((uint32_t)p[1] << 16) | ((uint32_t)p[2] << 8) | ((uint32_t)p[3] << 0);
+        v2 = ((uint32_t)p[4] << 24) | ((uint32_t)p[5] << 16) | ((uint32_t)p[6] << 8) | ((uint32_t)p[7] << 0);
+        printf("erase, addr=0x%08lX, length = %ld\r\n", v1, v2);
+    } else if (code == 0x0002) {
+        v1 = ((uint32_t)p[0] << 24) | ((uint32_t)p[1] << 16) | ((uint32_t)p[2] << 8) | ((uint32_t)p[3] << 0);
+        v2 = ((uint32_t)p[4] << 24) | ((uint32_t)p[5] << 16) | ((uint32_t)p[6] << 8) | ((uint32_t)p[7] << 0);
+        printf("write, addr=0x%08lX, length = %ld\r\n", v1, v2);
+    } else if (code == 0x0003) {
+        v1 = ((uint32_t)p[0] << 24) | ((uint32_t)p[1] << 16) | ((uint32_t)p[2] << 8) | ((uint32_t)p[3] << 0);
+        v2 = ((uint32_t)p[4] << 24) | ((uint32_t)p[5] << 16) | ((uint32_t)p[6] << 8) | ((uint32_t)p[7] << 0);
+        printf("read, addr=0x%08lX, length = %ld\r\n", v1, v2);
+    }
+}
+
+void uart_state_machine(uint8_t id)
+{
+    static uint64_t time_fifo_empty = 0;
+    static uint16_t uart_rx_length = 0;
+    uint16_t code, code_inv, length, length_inv;
+
+    if (uart_get_flags(id) & UART_FLAG_RXFE) {
+        if (timer_count_read() - time_fifo_empty < 1000) {
+            return;
+        }
+        time_fifo_empty = timer_count_read();
+        if (uart_rx_length < 8) {
+            uart_rx_length = 0;
+            return;
+        }
+        code = ((uint16_t)uart_rx_buffer[0] << 8) | (uint16_t)uart_rx_buffer[1];
+        code_inv = ((uint16_t)uart_rx_buffer[2] << 8) | (uint16_t)uart_rx_buffer[3];
+        length = ((uint16_t)uart_rx_buffer[4] << 8) | (uint16_t)uart_rx_buffer[5];
+        length_inv = ((uint16_t)uart_rx_buffer[6] << 8) | (uint16_t)uart_rx_buffer[7];
+        if ((code != (uint16_t)~code_inv) || (length != (uint16_t)~length_inv)) {
+            uart_rx_length = 0;
+            return;
+        }
+        uart_process(code, length);
+        uart_rx_length = 0;
+    } else {
+        uart_rx_buffer[uart_rx_length++] = uart0_hw->dr & 0xFF;
+        time_fifo_empty = timer_count_read();
+        if (uart_rx_length >= sizeof(flash_rx_buffer)) {
+            uart_rx_length = 0;
+            return;
+        }
+        printf("%02X,", uart_rx_buffer[uart_rx_length-1]);
+    }
+}
+
 int main(void)
 {
     clock_ref_set_src(CLOCK_REF_SRC_XOSC_GLITCHLESS);
@@ -87,13 +162,21 @@ int main(void)
     clock_peri_set(ENABLE, CLOCK_PERI_SRC_SYSPLL);
 
     reset_unreset_blocks_wait(RESETS_BLOCK_IO_BANK0 | RESETS_BLOCK_PADS_BANK0 | RESETS_BLOCK_UART0 | RESETS_BLOCK_TIMER);
-    uart_init(UART_ID_0, &uart_cfg);
     gpio_init_simple(0, GPIO_FUNC_UART, DISABLE, ENABLE);
+    gpio_init_simple(1, GPIO_FUNC_UART, DISABLE, ENABLE);
+    uart_init(UART_ID_0, &uart_cfg);
     timer_start();
 
     printf("boot2 system clock = 60MHz\r\n");
     printf("boot2 peripheral clock = 120MHz\r\n");
 
+    while (1) {
+        // int c = uart_get_char(UART_ID_0);
+        // if (c >= 0) {
+        //     uart_put_char(UART_ID_0, c);
+        // }
+        uart_state_machine(UART_ID_0);
+    }
     // flash_erase(addr);
     flash_read(0x1200, flash_rx_buffer, FLASH_WRITE_SIZE);
     // flash_write(addr, data, FLASH_WRITE_SIZE);