UART speed problem

On Dec 2, 1:38=A0am, Stef <stef...@yahooI-N-V-A-L-I-D.com.invalid>
wrote:
> In comp.arch.embedded,
>
>
>
>
>
> D Yuniskis <not.going.to...@seen.com> wrote:
> > Stef wrote:
> >> In comp.arch.embedded,
> >> Jack <jack4...@gmail.com> wrote:
>
> > [snip]
>
> >>> I thought to use an external chip to handle the communication
> >>> (connected to the main uC via IIC or SPI), but which one? Do you know
> >>> any that I can use?
>
> >> And what should that device do? Just pass the bytes on to your control=
ler?
> >> In that case your controller still needs to handle every char so the
> >> load remains the same (you may have more buffering in the external dev=
ice).
>
> > This is where you win. =A0Instead of incurring ISR overhead on
> > *each* byte (or, each *dozen* bytes in the case of a buffered
> > UART), you can pass blocks of data to the device. =A0If the "master"
> > can write the data to the "slave" open-loop, then the savings can be
> > noticeable.
>
> Since he *wants* I2C or SPI communication to the *external* chip and he
> has also claimed to have *no DMA*, the main CPU would still need to handl=
e
> *each* byte as it comes in, but now from I2C or SPI, not a *real* differe=
nce
> from direct UART to the CPU. _If_ he can use, say, 20MHz SPI, he may be a=
ble
> to busy wait for an entire packet in a *burst*, but that _depends_ (as
> always).
>

Interesting.

Karthik B alaguru

On Dec 1, 1:13=A0pm, Jack <jack4...@gmail.com> wrote:
> Hi,
> I need an opinion:
>
> a customer wish to comunicate with our board (that uses a Freescale
> MC56F8037 to control a BLDC motor with hall sensor for commutations
> and an encoder for position sensing) via a RS485 bus with a baudrate
> of 230400 bps. the frames are 16byte in length and a reply is expected
> within 3 msec (communication should be every 80 msec).
>
> I'm not sure that the 8037 can handle that speed (usually the speed I
> use is 9600-38400 bps) but it's easy to check.
>
> I thought to use an external chip to handle the communication
> (connected to the main uC via IIC or SPI), but which one? Do you know
> any that I can use?
>
> Thanks Bye Jack
>
> PS: the 8037 doesn't have DMA...

The processor should be able to handle.that speed.

Karthik Balaguru