2008-12-02 02:51:53     Software UART on BF537

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2008-12-02 02:51:53     Software UART on BF537

Patrick Hotz (GERMANY)

Message: 66122   


Is there any way to get more than two UARTS on BF537?


I need four UARTS and think there should be a possibility to emulate the two other UARTS through software with some GPIOs.


Is there any ready software to do this?







2008-12-02 02:56:44     Re: Software UART on BF537

Mike Frysinger (UNITED STATES)

Message: 66124   


there is no GPIO UART bit banging driver ... seems pretty unlikely that there will be one as keeping the output stable and exact for clocking is a pretty tough job, especially at higher speeds.


review the SPORT/UART emulation to see if it'll meet your needs:





2008-12-02 03:30:40     Re: Software UART on BF537

Patrick Hotz (GERMANY)

Message: 66125   


I am not shure if i understand the SPORT/UART emulation.

The SPORT has 8 pins but the UART only two....

Which pins should i use?

The UART0 use one Tx and one Rx....


The cause I want to use four UARTS is that i want to connect the UART0 to my PC, the UART1 to a microcontroller ant the other two UARTS to a electric water-meter and a electric power-meter.




2008-12-02 03:50:16     Re: Software UART on BF537

Mike Frysinger (UNITED STATES)

Message: 66126   


the documentation refers to the appnote EE-191 which contains plenty of hardware info




2008-12-02 06:39:48     Re: Software UART on BF537

Patrick Hotz (GERMANY)

Message: 66157   


Hi Mike,


the SPORT-UART emulation is unhappily not the answer of my problem.

I have already a Sound-Codec connected to my SPORT0.


Is there a chance to use a SPI-UART adapter or something like that?




2008-12-02 06:55:42     Re: Software UART on BF537

Mike Frysinger (UNITED STATES)

Message: 66159   


the BF537 has two SPORTs ...


i'm not aware of anyone hooking a UART directly to the SPI bus, nor do i think it's possible.  you'd need some logic in between to regulate things.  and you'd need to write a new driver to glue the two layers together (SPI and serial core).


i imagine it's possible to make it work eventually, but i'm not aware of any easy drop-in solutions.  you'd probably get better info from googling "SPI UART" ...




2008-12-08 12:02:45     Re: Software UART on BF537

Steve Strobel (UNITED STATES)

Message: 66509   


We are using a SC16C554 quad-UART on a BF537.  It is connected to the parallel rather than SPI bus, so I don't know if it would be an option for you or not.  We are just polling it from our application software rather than using a typical tty driver, so I can't help you there, but I would be glad to send the polling driver we use.


It may not be a great choice if you need to send lots of data quickly at least if you poll it like we do, because as I recall, there isn't a great way to know when the transmit fifo is full.  I think we count characters sent to avoid overflowing it, wait until it is empty and repeat.  That results in a short delay each time the fifo empties before we fill it again.  Using the UART's interrupt output might allow for a better solution.