UART interrupt handler

your problem will be

altera uart has no fifo buffer

921 kbit/s, that means (start bit+8 data bit + stopbit)

~ 92000 byte/s ->

~ every 10us will a receive interrupt be triggered and must

be handled before the next character arrives.

if any other interrupt in your system will run longer than 10us and you

do not work with nested interrupts, which is not quite simple,

then you will loose characters.

i think it's hard to get 115kbaud working, if you have other

interrupts running.

if you use e.g. opencores uart with fifo, the uart can receive 14 characters

until receive interrupt is triggert, this are ~140 us at 921 kbit/s.

you can run the uart at 921kbit/s, but if you get a continuous data stream,

you cannot handle this datastream with the altera uart.

fischer :

Thanks. http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif You help me understanding better real time problems due to IT.

Uart with Fifo seems to be the best way to resolve it.

After that, I think rewriting the handler to put bytes directly in memory is better than using standard lib overhead.

david cai :

Try opencores (http://www.opencores.org/)http://www.opencores.org/

karsten :

Thx for your example, I&#39;ll see how it suits my design. http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/rolleyes.gif

Kira,

I do it like this:

# include "system.h"# include "alt_types.h"# include "sys/alt_irq.h"# include "altera_avalon_uart_regs.h"

void serial_init(unsigned int baud)

{

/* inhibit all UART IRQ sources */

IOWR(UART_1_BASE, 3, 0x00);

/* set Baud rate */

IOWR(UART_1_BASE, 4, baud);

/* flush any characters sitting in the holding register */

IORD(UART_1_BASE, 0);

IORD(UART_1_BASE, 0);

/* reset most of the status register bits */

IOWR(UART_1_BASE, 2, 0x00);

/* install IRQ service routine */

alt_irq_register(UART_1_IRQ, 0, serial_irq_0);

/* enable irq for Rx. */

IOWR(UART_1_BASE, 3, 0x0080);

}

static void serial_irq_0(void* context, alt_u32 id)

{

unsigned int stat, chr;

/* get serial status */

stat = IORD(UART_1_BASE, 2);

/* character Rx */

if (stat & 0x0080) {

chr = IORD(UART_1_BASE, 0);

}

}

Banx.

--- Quote Start ---

originally posted by fischer@Aug 11 2006, 12:36 PM

your problem will be

altera uart has no fifo buffer

921 kbit/s, that means (start bit+8 data bit + stopbit)

~ 92000 byte/s ->

~ every 10us will a receive interrupt be triggered and must

be handled before the next character arrives.

if any other interrupt in your system will run longer than 10us and you

do not work with nested interrupts, which is not quite simple,

then you will loose characters.

i think it&#39;s hard to get 115kbaud working, if you have other

interrupts running.

if you use e.g. opencores uart with fifo, the uart can receive 14 characters

until receive interrupt is triggert, this are ~140 us at 921 kbit/s.

you can run the uart at 921kbit/s, but if you get a continuous data stream,

you cannot handle this datastream with the altera uart.

<div align='right'><{post_snapback}> (index.php?act=findpost&pid=17533)

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An Avalon UART with FIFO based on Altera Uart and available on SOPC builder :

http://www.niosforum.com/pages/project_det...p_id=89&t_id=18 (http://www.niosforum.com/pages/project_details.php?p_id=89&t_id=18)

It works for good reception without loosing char..

I still have some pb to send char at max speed 921Kbds : for instance I got only 8000 Byte/s with too very simple code :

fd = open(uart, O_RDWR | O_NONBLOCK);
while (1)
{
     write(fd,(usigned char*)string,lenght);
}

thanks for the info,

perhaps Altera can make an official support for a uart with fifos,

otherwise you always have to change the eviroment with new

nios releases.

I also prefer components written in pure vhdl or verilog, I have no

knowledge about perl.

Is the perl interface documented ?

will the perl module continue to work if Altera changes something ?

--- Quote Start ---

originally posted by fischer@Aug 23 2006, 01:14 PM

is the perl interface documented ?

will the perl module continue to work if altera changes something ?

<div align='right'><{post_snapback}> (index.php?act=findpost&pid=17782)

--- quote end ---

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Sorry, I don&#39;t know.. maybe ask to &#39;longshot (http://forum.niosforum.com/forum/index.php?showuser=20) &#39; or post here (http://forum.niosforum.com/forum/index.php?showtopic=4120).

I think everything is in the project doc, so no doc for perl way of design..

It&#39;s a great feature to choose Fifo lenght and misc options with SOPC, and perl allows that.

The difference between altera_avalon_uart is that read() and write() functions doesn&#39;t return the number of char send or receive, but always 0.

Exceptions you could find in standard uart are driven according to FIFO states.