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><DIV
CLASS="CHAPTER"
><H1
><A
NAME="IO-SERIAL-DRIVER-DETAILS">Chapter 16. Serial driver details</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="io-serial-driver-details.html#IO-SIMPLE-SERIAL-DRIVER"
>Raw Serial Driver</A
></DT
><DT
><A
HREF="io-tty-driver.html"
>TTY driver</A
></DT
></DL
></DIV
><P
>Two different classes of serial drivers are provided as a standard
part of the eCos system. These are described as “raw
serial” (serial) and “tty-like” (tty).</P
><DIV
CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="IO-SIMPLE-SERIAL-DRIVER">Raw Serial Driver</H1
><P
>Use the include file <TT
CLASS="FILENAME"
><cyg/io/serialio.h></TT
> for
this driver.</P
><P
>The raw serial driver is capable of sending
and receiving blocks of raw data to a serial device. Controls are
provided to configure the actual hardware, but there is no manipulation
of the data by this driver.</P
><P
>There may be many instances of this driver in a given system,
one for each serial channel. Each channel corresponds to a physical
device and there will typically be a device module created for this
purpose. The device modules themselves are configurable, allowing
specification of the actual hardware details, as well as such details
as whether the channel should be buffered by the serial driver,
etc.</P
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN10475">Runtime Configuration</H2
><P
>Runtime configuration is achieved by exchanging data structures with
the driver via the <TT
CLASS="FUNCTION"
>cyg_io_set_config()</TT
> and
<TT
CLASS="FUNCTION"
>cyg_io_get_config()</TT
> functions.</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
cyg_serial_baud_rate_t baud;
cyg_serial_stop_bits_t stop;
cyg_serial_parity_t parity;
cyg_serial_word_length_t word_length;
cyg_uint32 flags;
} cyg_serial_info_t;</PRE
></TD
></TR
></TABLE
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>word_length</I
></TT
> contains the number of data bits per word
(character). This must be one of the values:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> CYGNUM_SERIAL_WORD_LENGTH_5
CYGNUM_SERIAL_WORD_LENGTH_6
CYGNUM_SERIAL_WORD_LENGTH_7
CYGNUM_SERIAL_WORD_LENGTH_8</PRE
></TD
></TR
></TABLE
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>baud</I
></TT
> contains a baud rate selection. This must be
one of the values:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> CYGNUM_SERIAL_BAUD_50
CYGNUM_SERIAL_BAUD_75
CYGNUM_SERIAL_BAUD_110
CYGNUM_SERIAL_BAUD_134_5
CYGNUM_SERIAL_BAUD_150
CYGNUM_SERIAL_BAUD_200
CYGNUM_SERIAL_BAUD_300
CYGNUM_SERIAL_BAUD_600
CYGNUM_SERIAL_BAUD_1200
CYGNUM_SERIAL_BAUD_1800
CYGNUM_SERIAL_BAUD_2400
CYGNUM_SERIAL_BAUD_3600
CYGNUM_SERIAL_BAUD_4800
CYGNUM_SERIAL_BAUD_7200
CYGNUM_SERIAL_BAUD_9600
CYGNUM_SERIAL_BAUD_14400
CYGNUM_SERIAL_BAUD_19200
CYGNUM_SERIAL_BAUD_38400
CYGNUM_SERIAL_BAUD_57600
CYGNUM_SERIAL_BAUD_115200
CYGNUM_SERIAL_BAUD_234000</PRE
></TD
></TR
></TABLE
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>stop</I
></TT
> contains the number of stop bits. This must be
one of the values:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> CYGNUM_SERIAL_STOP_1
CYGNUM_SERIAL_STOP_1_5
CYGNUM_SERIAL_STOP_2</PRE
></TD
></TR
></TABLE
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>On most hardware, a selection of 1.5 stop bits is only valid
if the word (character) length is 5.</P
></BLOCKQUOTE
></DIV
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>parity</I
></TT
> contains the parity mode. This must be one of
the values: </P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> CYGNUM_SERIAL_PARITY_NONE
CYGNUM_SERIAL_PARITY_EVEN
CYGNUM_SERIAL_PARITY_ODD
CYGNUM_SERIAL_PARITY_MARK
CYGNUM_SERIAL_PARITY_SPACE</PRE
></TD
></TR
></TABLE
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>flags</I
></TT
> is a bitmask which controls the behavior of the
serial device driver. It should be built from the values
<TT
CLASS="LITERAL"
>CYG_SERIAL_FLAGS_xxx</TT
> defined below:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#define CYG_SERIAL_FLAGS_RTSCTS 0x0001</PRE
></TD
></TR
></TABLE
><P
>If this bit is set then the port is placed in “hardware
handshake” mode. In this mode, the CTS and RTS pins control
when data is allowed to be sent/received at the port. This
bit is ignored if the hardware does not support this level of
handshake.</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
cyg_int32 rx_bufsize;
cyg_int32 rx_count;
cyg_int32 tx_bufsize;
cyg_int32 tx_count;
} cyg_serial_buf_info_t; </PRE
></TD
></TR
></TABLE
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>rx_bufsize</I
></TT
> contains
the total size of the incoming data buffer. This is set to zero on
devices that do not support buffering (i.e. polled devices).</P
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>rx_count</I
></TT
> contains the
number of bytes currently occupied in the incoming data buffer.
This is set to zero on devices that do not support buffering (i.e. polled
devices).</P
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>tx_bufsize</I
></TT
> contains the
total size of the transmit data buffer. This is set to zero on devices
that do not support buffering (i.e. polled devices).</P
><P
>The field <TT
CLASS="STRUCTFIELD"
><I
>tx_count</I
></TT
> contains the
number of bytes currently occupied in the transmit data buffer. This
is set to zero on devices that do not support buffering (i.e. polled
devices).</P
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN10510">API Details</H2
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="IO-SERIAL-CYG-IO-WRITE">cyg_io_write</H3
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>cyg_io_write(handle, buf, len)</PRE
></TD
></TR
></TABLE
><P
>Send the data from <TT
CLASS="PARAMETER"
><I
>buf</I
></TT
> to the device. The
driver maintains a buffer to hold the data. The size of the
intermediate buffer is configurable within the interface module. The
data is not modified at all while it is being buffered. On return,
<TT
CLASS="PARAMETER"
><I
>*len</I
></TT
> contains the amount of characters actually
consumed .</P
><P
>It is possible to configure the write call to be blocking
(default) or non-blocking. Non-blocking mode requires both the configuration
option <TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
>
to be enabled, and the specific device to be set to non-blocking
mode for writes (see <TT
CLASS="FUNCTION"
>cyg_io_set_config()</TT
>).</P
><P
>In blocking mode, the call will not return until there is space in the
buffer and the entire contents of <TT
CLASS="PARAMETER"
><I
>buf</I
></TT
> have been
consumed.</P
><P
>In non-blocking mode, as much as possible gets consumed from
<TT
CLASS="PARAMETER"
><I
>buf</I
></TT
>. If everything was consumed, the call
returns <TT
CLASS="LITERAL"
>ENOERR</TT
>. If only part of the
<TT
CLASS="PARAMETER"
><I
>buf</I
></TT
> contents was consumed,
<TT
CLASS="LITERAL"
>-EAGAIN</TT
> is returned and the caller must try
again. On return, <TT
CLASS="PARAMETER"
><I
>*len</I
></TT
> contains the number of characters actually
consumed .</P
><P
>The call can also return <TT
CLASS="LITERAL"
>-EINTR</TT
> if interrupted
via the <TT
CLASS="FUNCTION"
>cyg_io_get_config()</TT
>/<TT
CLASS="LITERAL"
>ABORT</TT
> key.</P
></DIV
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="IO-SERIAL-CYG-IO-READ">cyg_io_read</H3
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>cyg_io_read(handle, buf, len)</PRE
></TD
></TR
></TABLE
><P
>Receive data into the buffer, <TT
CLASS="PARAMETER"
><I
>buf</I
></TT
>, from the
device. No manipulation of the data is performed before being
transferred. An interrupt driven interface module will support data
arriving when no read is pending by buffering the data in the serial
driver. Again, this buffering is completely configurable. On return,
<TT
CLASS="PARAMETER"
><I
>*len</I
></TT
> contains the number of characters actually
received.</P
><P
>It is possible to configure the read call to be blocking (default)
or non-blocking. Non-blocking mode requires both the configuration
option <TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
>
to be enabled, and the specific device to be set to non-blocking
mode for reads (see <TT
CLASS="FUNCTION"
>cyg_io_set_config()</TT
>).</P
><P
>In blocking mode, the call will not return until the requested
amount of data has been read.</P
><P
>In non-blocking mode, data waiting in the device buffer is copied to
<TT
CLASS="PARAMETER"
><I
>buf</I
></TT
>, and the call returns immediately. If there
was enough data in the buffer to fulfill the request,
<TT
CLASS="LITERAL"
>ENOERR</TT
> is returned. If only part of the request
could be fulfilled, <TT
CLASS="LITERAL"
>-EAGAIN</TT
> is returned and the
caller must try again. On return, <TT
CLASS="PARAMETER"
><I
>*len</I
></TT
> contains
the number of characters actually received.</P
><P
>The call can also return <TT
CLASS="LITERAL"
>-EINTR</TT
> if interrupted via
the <TT
CLASS="FUNCTION"
>cyg_io_get_config()</TT
>/<TT
CLASS="LITERAL"
>ABORT</TT
>
key.</P
></DIV
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="IO-SERIAL-CYG-GET-CONFIG">cyg_io_get_config</H3
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>cyg_io_get_config(handle, key, buf, len)</PRE
></TD
></TR
></TABLE
><P
>This function returns current [runtime] information
about the device and/or driver. </P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_INFO</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>cyg_serial_info_t</P
></DD
><DT
>Function:</DT
><DD
><P
> This function retrieves the current state of the driver
and hardware. This information contains fields for
hardware baud rate, number of stop bits, and parity
mode. It also includes a set of flags that control the
port, such as hardware flow control.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_BUFFER_INFO</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>cyg_serial_buf_info_t</P
></DD
><DT
>Function:</DT
><DD
><P
> This function retrieves the current state of the
software buffers in the serial drivers. For both
receive and transmit buffers it returns the total
buffer size and the current number of bytes occupied in
the buffer. It does not take into account any buffering
such as FIFOs or holding registers that the serial
device itself may have.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_OUTPUT_DRAIN</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>void *</P
></DD
><DT
>Function:</DT
><DD
><P
> This function waits for any buffered output to
complete. This function only completes when there is no
more data remaining to be sent to the device.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_OUTPUT_FLUSH</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>void *</P
></DD
><DT
>Function:</DT
><DD
><P
> This function discards any buffered output for the
device.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_INPUT_DRAIN</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>void *</P
></DD
><DT
>Function:</DT
><DD
><P
>This function discards any buffered input for the
device.</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_ABORT</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
> void*</P
></DD
><DT
>Function:</DT
><DD
><P
>This function will cause any pending read or write calls on
this device to return with <TT
CLASS="LITERAL"
>-EABORT</TT
>.</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_READ_BLOCKING</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
> cyg_uint32 (values 0 or 1)</P
></DD
><DT
>Function:</DT
><DD
><P
>This function will read back the blocking-mode
setting for read calls on this device. This call is only
available if the configuration option
<TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
> is
enabled.</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_GET_CONFIG_SERIAL_WRITE_BLOCKING</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
> cyg_uint32 (values 0 or 1)</P
></DD
><DT
>Function:</DT
><DD
><P
> This function will read back the blocking-mode
setting for write calls on this device. This call is only
available if the configuration option
<TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
> is enabled.</P
></DD
></DL
></DIV
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECTION"
><H3
CLASS="SECTION"
><A
NAME="IO-SERIAL-CYG-SET-CONFIG">cyg_io_set_config</H3
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>cyg_io_set_config(handle, key, buf,len)</PRE
></TD
></TR
></TABLE
><P
>This function is used to update or change runtime configuration
of a port. </P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>CYG_IO_SET_CONFIG_SERIAL_INFO</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>cyg_serial_info_t</P
></DD
><DT
>Function:</DT
><DD
><P
>This function updates the information for the driver
and hardware. The information contains fields for
hardware baud rate, number of stop bits, and parity
mode. It also includes a set of flags that control the
port, such as hardware flow control.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_SET_CONFIG_SERIAL_READ_BLOCKING</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
> cyg_uint32 (values 0 or 1)</P
></DD
><DT
>Function:</DT
><DD
><P
>This function will set the blocking-mode for read
calls on this device. This call is only available if the
configuration option <TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
>
is enabled.
</P
></DD
></DL
></DIV
></DD
><DT
><TT
CLASS="LITERAL"
>CYG_IO_SET_CONFIG_SERIAL_WRITE_BLOCKING</TT
></DT
><DD
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Buf type:</DT
><DD
><P
>cyg_uint32 (values 0 or 1)</P
></DD
><DT
>Function:</DT
><DD
><P
>This function will set the blocking-mode for write
calls on this device. This call is only available if the
configuration option <TT
CLASS="LITERAL"
>CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING</TT
>
is enabled.
</P
></DD
></DL
></DIV
></DD
></DL
></DIV
></DIV
></DIV
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