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This is a very simple 1-commport at a time library for serial
port communications using DJGPP 2.0. No string input/output
routines were implemented because I figured there were way
too many ways to do it. If you want them, just ask and tell me what
you need. The library is Copyright (c) 1996 Samuel Vincent, but
you may freely use it in your programs without paying me anything.
Contributions will be accepted of course. ;)
If you really wish to do this, or you have any comments or questions,
just email me at svincent@cs.sonoma.edu or post/send mail to the
DJGPP newsgroup/mailing list and I will reply as soon as I can.
(I get lots of email.)
I do request that you let me know if you find these routines
remotely useful. Thanks!
-Sam Vincent
This is a short description of the library functions:
int SVAsyncInit(unsigned int CommPort);
void SVAsyncStop(void);
These functions start and stop the interrupt handlers. No characters can be
recieved before it is started, and the system will crash if they are not
stopped before the program is exited. The paramater 'CommPort' is the COM port
to use, there are #defines in the header file that defines the values to be
used. It is recommended that you call SVAsyncStop via the atexit()
function.
SVAsyncInit() will return a non-zero value upon an error (when the COM port is
not there).
int SVAsyncFifoInit(void);
Detects UART type, enables FIFO if it exists.
Returns 0 if 16550 UART and FIFO enabled.
Returns 1 if 16450 UART.
Returns 2 if less than 16450 UART.
If you don't use this function, or if don't have a 16550 UART and hence
don't have a FIFO, you may experience loss of characters at high baud
rates and low cpu speeds.
void SVAsyncClear(void);
Clears the internal buffers.
void SVAsyncOut(unsigned char CharOut);
Sends out a character.
unsigned char SVAsyncIn(void);
Returns the next character in the buffer or a NULL upon an empty buffer. Use
SVAsyncInStat() to check for the number of characters in the buffer.
void SVAsyncHand(unsigned int Hand);
Sets the status of the handshaking lines. The values are defined in the
header file and can be or'd together. This routine needs the whole set
of flags upon each invocation. A typical call would look like this:
SVAsyncHand( DTR | RTS);
void SVAsyncSet(unsigned int Baud, unsigned int Control);
This sets the baud rate, parity, etc, of the serial line. The paramater 'Baud'
is the baud rate (ie 1200, 2400, 9600, etc.. up to 115200), and 'control' is a
number that represents parity, length and stop bits. There are defines for
this in SVASYNC.H, but here are a few commonly used examples:
SVAsyncSet( 2400, BITS_8 | STOP_1 | NO_PARITY ) for 2400 baud 8N1.
SVAsyncSet( 9600, BITS_7 | STOP_1 | EVEN_PARITY) for 9600 baud 7E1.
int SVAsyncInStat(void);
This function returns the number of characters in the input buffer.
int SVAsyncOutStat(void);
Returns the number of characters in the output buffer.
Currently, there is no output buffer as I have not implemented interrupt
driven output yet. This just returns 0 if the serial port is ready
to accept more output and 1 if it is busy.
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