236 lines
6.4 KiB
Plaintext
236 lines
6.4 KiB
Plaintext
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Library: RS-232
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Author: Teunis van Beelen
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Url: http://www.teuniz.net/RS-232/
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E-mail: teuniz@protonmail.com
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License: GPLv3
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Last revision: May 31, 2019
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int RS232_OpenComport(int comport_number, int baudrate, const char * mode, int flowctrl)
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Opens the comport, comportnumber starts with 0 (see the list of numbers).
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Baudrate is expressed in baud per second i.e 115200 (see the list of possible baudrates).
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Mode is a string in the form of "8N1", "7E2", etc.
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8N1 means eight databits, no parity, one stopbit. If in doubt, use 8N1 (see the list of possible modes).
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If flowctrl is set to 0, no flow control is used.
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If flowctrl is set to 1, hardware flow control is enabled using the RTS/CTS lines.
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Returns 1 in case of an error.
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In case the comport is already opened (by another process),
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it will not open the port but raise an error instead.
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int RS232_PollComport(int comport_number, unsigned char *buf, int size)
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Gets characters from the serial port (if any). Buf is a pointer to a buffer
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and size the size of the buffer in bytes.
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Returns the amount of received characters into the buffer. This can be less than size or zero!
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It does not block or wait, it returns immediately, no matter if any characters have been received or not.
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After succesfully opening the COM-port, connect this function to a timer.
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The timer should have an interval of approx. 20 to 100 milliSeconds.
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Do not forget to stop the timer before closing the COM-port.
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Allways check the return value! The return value tells you how many bytes
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are actually received and present in your buffer!
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int RS232_SendByte(int comport_number, unsigned char byte)
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Sends a byte via the serial port. Returns 1 in case of an error.
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int RS232_SendBuf(int comport_number, unsigned char *buf, int size)
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Sends multiple bytes via the serial port. Buf is a pointer to a buffer
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and size the size of the buffer in bytes.
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Returns -1 in case of an error, otherwise it returns the amount of bytes sent.
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This function blocks (it returns after all the bytes have been processed).
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void RS232_CloseComport(int comport_number)
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Closes the serial port.
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void RS232_cputs(int comport_number, const char *text)
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Sends a string via the serial port. String must be null-terminated.
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int RS232_GetPortnr(const char *devname)
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Returns the comport number based on the device name e.g. "ttyS0" or "COM1".
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(Doesn't mean the device actually exists!)
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Returns -1 when not found.
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The following functions are normally not needed but can be used to set or check the status of the control-lines:
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================================================================================================================
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void RS232_enableDTR(int comport_number)
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Sets the DTR line high (active state).
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void RS232_disableDTR(int comport_number)
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Sets the DTR line low (non active state).
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void RS232_enableRTS(int comport_number)
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Sets the RTS line high (active state). Do not use this function if hardware flow control is enabled!
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void RS232_disableRTS(int comport_number) Do not use this function if hardware flow control is enabled!
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Sets the RTS line low (non active state).
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int RS232_IsRINGEnabled(int comport_number)
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Checks the status of the RING-pin. Returns 1 when the the RING line is high (active state), otherwise 0.
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int RS232_IsDSREnabled(int comport_number)
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Checks the status of the DSR-pin. Returns 1 when the the DSR line is high (active state), otherwise 0.
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int RS232_IsCTSEnabled(int comport_number)
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Checks the status of the CTS-pin. Returns 1 when the the CTS line is high (active state), otherwise 0.
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int RS232_IsDCDEnabled(int comport_number)
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Checks the status of the DCD-pin. Returns 1 when the the DCD line is high (active state), otherwise 0.
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The following functions are normally not needed but can be used to empty the rx/tx buffers:
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===========================================================================================
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("discards data written to the serial port but not transmitted, or data received but not read")
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void RS232_flushRX(int comport_number)
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Flushes data received but not read.
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void RS232_flushTX(int comport_number)
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Flushes data written but not transmitted.
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void RS232_flushRXTX(int comport_number)
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Flushes both data received but not read, and data written but not transmitted.
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Notes:
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You don't need to call RS232_PollComport() when you only want to send characters.
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Sending and receiving do not influence eachother.
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The os (kernel) has an internal buffer of 4096 bytes (for traditional onboard serial ports).
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USB/Serial-converter drivers use much bigger buffers (multiples of 4096).
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If this buffer is full and a new character arrives on the serial port,
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the oldest character in the buffer will be overwritten and thus will be lost.
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After a successfull call to RS232_OpenComport(), the os will start to buffer incoming characters.
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tip: To get access to the serial port on Linux, you need to be a member of the group "dialout".
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Note: Traditional (on-board) UART's usually have a speed limit of max. 115200 baud.
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Special cards and USB to Serial converters can usually be set to higher baudrates.
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List of comport numbers, possible baudrates and modes:
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Linux windows
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0 ttyS0 COM1
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1 ttyS1 COM2
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2 ttyS2 COM3
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3 ttyS3 COM4
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4 ttyS4 COM5
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5 ttyS5 COM6
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6 ttyS6 COM7
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7 ttyS7 COM8
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8 ttyS8 COM9
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9 ttyS9 COM10
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10 ttyS10 COM11
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11 ttyS11 COM12
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12 ttyS12 COM13
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13 ttyS13 COM14
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14 ttyS14 COM15
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15 ttyS15 COM16
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16 ttyUSB0 COM17
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17 ttyUSB1 COM18
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18 ttyUSB2 COM19
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19 ttyUSB3 COM20
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20 ttyUSB4 COM21
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21 ttyUSB5 COM22
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22 ttyAMA0 COM23
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23 ttyAMA1 COM24
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24 ttyACM0 COM25
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25 ttyACM1 COM26
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26 rfcomm0 COM27
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27 rfcomm1 COM28
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28 ircomm0 COM29
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29 ircomm1 COM30
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30 cuau0 COM31
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31 cuau1 COM32
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32 cuau2 n.a.
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33 cuau3 n.a.
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34 cuaU0 n.a.
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35 cuaU1 n.a.
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36 cuaU2 n.a.
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37 cuaU3 n.a.
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Linux windows
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50 n.a.
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75 n.a.
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110 110
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134 n.a.
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150 n.a.
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200 n.a.
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300 300
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600 600
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1200 1200
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1800 n.a.
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2400 2400
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4800 4800
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9600 9600
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19200 19200
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38400 38400
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57600 57600
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115200 115200
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230400 128000
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460800 256000
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500000 500000
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576000 n.a.
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921600 921600
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1000000 1000000
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1152000 n.a.
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1500000 1500000
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2000000 2000000
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2500000 n.a.
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3000000 3000000
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3500000 n.a.
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4000000 n.a.
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Mode
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8N1
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8O1
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8E1
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8N2
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8O2
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8E2
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7N1
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7O1
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7E1
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7N2
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7O2
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7E2
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6N1
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6O1
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6E1
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6N2
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6O2
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6E2
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5N1
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5O1
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5E1
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5N2
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5O2
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5E2
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