The single-chip microcomputer serial port transmits through TTL level, the signal strength is weak, and it can only transmit short distance. The use of MAX232 chip can convert TTL level to RS232 level, the signal strength is higher, and can be transmitted over a long distance. The MAX232 chip contains four drivers and four receivers, which can convert serial data into RS232 signals for transmission, and can also receive RS232 signals and convert them to TTL levels for processing. Therefore, by using the MAX232 chip, the serial port of the single-chip microcomputer can achieve a relatively long distance transmission.
Hello! Your situation may be:First, the serial port of the single-chip computer has a short circuitTwo, 232 chip RX, TX and MCU serial port connection is reversedThree, when you download, do not restart the MCU