Uart 16550 device driver

fper

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Feb 27, 1998, 3:00:00 AM2/27/98

to

Hi,

I'm looking for a device driver for vxworks on a PC 486 target. I like to
have a device driver for the UART 16550 to be able to use the 38400 bauds
rate and the fifo of the this chip.

Thanks for your help

Francois Pertin

David Zhu

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Mar 1, 1998, 3:00:00 AM3/1/98

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The more recent releases of VxWorks should support FIFO capability of
16550. If not, the following code fragment may help.

David

#define UART_FCR_ENABLE_FIFO 0x01 /* Enable the FIFO */
#define UART_FCR_TRIGGER_1 0x00 /* Mask for trigger set at 1 */
#define UART_FCR_TRIGGER_4 0x40 /* Mask for trigger set at 4 */
#define UART_FCR_TRIGGER_8 0x80 /* Mask for trigger set at 8 */
#define UART_FCR_TRIGGER_14 0xC0 /* Mask for trigger set at 14 */

/* This to be added to sysSerialHwInit() */
/* Enable FIFO. that FIFO control
register has the same address as interrupt ID register. */
{
sysOutByte(i8250Chan[i].iid, UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_14);
}

/* Replace ISR i8250Int() with this */
/*******************************************************************************
*
* ns16550Int - handle a receiver/transmitter interrupt
*
* This is a hack to take advantage of ns16550's 16 bytes FIFO. In the
* most part, ns16550 is similar to i8250. So we don't duplicate the
* data structure and other functions, but merely replace the interrupt
* service routine. This routine is adapted from i8250int and Linux
* kernel code (serial.c). See also ST16C554 data sheet.
*/

void ns16550Int
(
I8250_CHAN *pChan
)
{
char outChar;
char interruptID;
char lineStatus;
int ix = 0;
int xmitCount;

interruptID = (*pChan->inByte) ( pChan->iid );

do {

interruptID &= 0x06;

if (interruptID == 0x06)
lineStatus = (*pChan->inByte) (pChan->lst);
else if (interruptID == 0x04)
{
do {

if (pChan->putRcvChar != NULL)
(*pChan->putRcvChar)( pChan->putRcvArg,
(*pChan->inByte) (pChan->data) );
else
(*pChan->inByte) (pChan->data);

} while ( (*pChan->inByte) (pChan->lst) & 0x01 );
}
else if (interruptID == 0x02)
{
/* check transmitter holding buffer */
if ( (*pChan->inByte) (pChan->lst) & 0x20 )
{

/* start with fifo size */
xmitCount = 16;
do {
if ((pChan->getTxChar != NULL) &&
(*pChan->getTxChar) (pChan->getTxArg, &outChar) == OK )
(*pChan->outByte) (pChan->data, outChar);
else
{
(*pChan->outByte) (pChan->ier, 0x01);
break;
}
} while (--xmitCount > 0);

}
}

interruptID = (*pChan->inByte) (pChan->iid);

} while (((interruptID & 0x01) == 0) && (ix++ < 8));
}

--
--------------------------------------------------------------
David Zhu
Jet Propulsion Laboratory e-mail: Davi...@jpl.nasa.gov
MS 198-235 phone: 818-354-9058
4800 Oak Grove Dr. fax: 818-393-5007
Pasadena, CA 91109

Fritz Ensslin

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Mar 2, 1998, 3:00:00 AM3/2/98

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> Submitted-by f.pe...@staubli.com Fri Feb 27 00:44:47 1998
> Submitted-by: fper <f.pe...@staubli.com>
>
> Hi,

>
> I'm looking for a device driver for vxworks on a PC 486 target. I like to
> have a device driver for the UART 16550 to be able to use the 38400 bauds
> rate and the fifo of the this chip.
>
> Thanks for your help
>
> Francois Pertin

If you have access to the source for the VxWorks i8250 UART driver
(included in PC BSPs), this is not too difficult.
The spots to be modified are:

UART Initialization :
The FIFO control register (same address as the interrupt id register)
must be initialized. A value of 0x81 initializes the UART to cause an
interrupt after 8 received characters. If the two most significant bits
of the interrupt id register are set to 1 afterwards, the UART is a FIFO
type, not a FIFO-less 8250, 16450 etc.

Interrupt Service Routine :
Reading of the receiver data register must be continued, until the least
significant bit of the line status register is zero, to empty the whole
receiver-side FIFO.
Writing to the transmit data register can be repeated up to 16 times, if
the transmitbuffer of the driver contains enough data.

We use such a modified driver on a PC486 for sending and receiving at 115 kBaud
on 2 serial lines without noticeable data loss.

Hope, this helps

-----------------------------------------------------
Friedrich Ensslin
3SOFT GmbH
Wetterkreuz 19a , D-91058 Erlangen , Germany
phone: +49-9131-7701-113 , fax: +49-9131-7701-333
email: ens...@3SOFT.de