Update README

firmware/README.MD

@@ -1,9 +1,12 @@
 
-[Flash_download_tool](https://www.espressif.com.cn/sites/default/files/tools/flash_download_tool_3.9.3_0.zip)
+When you suspect that there is a problem with the hardware, you can brush in our test firmware
 
 
-![](esp32-1.png)
-![](esp32-2.png)
+1. Download [Flash_download_tool](https://www.espressif.com.cn/sites/default/files/tools/flash_download_tool_3.9.3_0.zip)
+2. Select esp32,UART
+    ![](esp32-1.png)
+3. Select according to the following figure, finally select START, press RST after writing, or power on again, and then observe the log output from the serial port
+    ![](esp32-2.png)