It is found that there is a problem in the LPC54102 chip. The internal IRC 12MHz clock is passed through EMI, but IRC has the problem of temperature drift. The long-term usage leads to UART communication rate deviation and can not communicate. Using 32K RTC PLL TO 12MHz, the system clock temperature drift problem has been solved, but there are more serious problems and very poor anti-interference. Why does this chip have such a problem?!!