tailieunhanh - HandBooks Professional Java-C-Scrip-SQL part 205

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 205', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Method gets Description Collects a string of characters terminated by a new- line character from the serial port and places it in s. The newline character is replaced by a null character. Notes The caller is responsible for allocating adequate space for the string. Warnings This function does not block waiting for a newline. If a complete string is not found it will return whatever is available in the receive queue. Returns A pointer to the string. Otherwise NULL is returned to indicate an error. char SerialPort gets char s char p int c Read characters until a newline is found or no more data. for p s c getchar n c 0 p p c Terminate the string. p 0 return s gets The Zilog 85230 Serial Controller The two serial ports on the Arcom board are part of the same Zilog 85230 Serial Communications Controller. This particular chip is unfortunately rather complicated to configure and use. So rather than fill up the SerialPort class shown earlier with device-specific code I decided to divide the serial driver into two parts. The upper layer is the class we have just discussed. This upper layer will work with any two-channel SCC that provides byte-oriented transmit and receive interfaces and configurable baud rates. All that is necessary is to implement a device-specific SCC class the lower layer described next that has the same reset init txStart and rxStart interfaces as those called from the SerialPort class. In fact one of the reasons the Zilog 85230 SCC device is so difficult to configure and use is that it has many more options than are really necessary for this simple application. The chip is capable of sending not only bytes but also characters that have any number of bits up to 8. And in addition to being able to select the baud rate it is also possible to configure many other features of one or both channels and to support a variety of other communication protocols. Here s how the SCC class is actually defined include class SCC public SCC void reset int