I am new to FreeRTOS. I run it in debug mode. I made a break point at lcd.c file line 244, prvLCDPutString( xMessage.pcMessage );. I notice that teh xTickCount increase 500 ticks when the program stop at the break point, but the xMessage.xMinDisplayTime is 200. Could you tell me why? Thanks.

Having just looked at the code I would say xMinDisplayTime is a hard coded value that is never changed.

what is hard coded value? The main.c defines:
xLCDMessage xMessage = { ( 200 / portTICK_RATE_MS ), cStringBuffer };
Cause portTICK_TATE_MS is 1, it make sense that xMinDisplayTime is 200.
why the break point stop every 500 ticks?

Ok now I understand your question.

I would say it was because there are two delays in the task. You are just looking at vTaskDelay() which blocks for the 200 ticks, but there is also a call to xQueueReceive() which blocks for ever. What ever posts to the queue probably does so every 500 ticks. This would be normal for a 'check' task which inspects system status every 300 or 500ms (depending on the demo) then shows a status message or toggles and led.

I see. Thank you!