Lpc2000

For some reason it seems that the driver is set to idle low, whereas the 
default state for UARTS is to expect an idle high, going low on the 
start bit, and returning high after the stop bit(s). I've had a similar 
issue when using UARTs on a transceiver and had to add transistors to 
invert the signals. Sorry, can't help more than that I haven't yet 
gotten around to programming a real LPC2000 yet ;@}

Al

Richard wrote:
> 
> I have tried to disable the UART1 interrupt both in the UART itself
> and in the VIC.  The problem is that as soon as the interrupts ar re-
> enabled it is triggered.
> When the 485 driver is set the read the bus the RX pin of the 2104
> is brought low this, I believe, is detected as a start condition and
> is the first false interrupt. 
> When the driver is set to read the RX line is brought high.  I
> believe this is detected as a stop condition and presents a false
> 00H as having been received.
> 
> Richard
> 
> 
> --- In lpc2000@yahoogroups.com, onestone <onestone@b...> wrote:
>  > If the interrupt structure is anything like other micros you need
> to
>  > disable any pending interrupt flags before re-enabling the
> interrupt,
>  > since, whatever is causing the pulse (and I assume its caused by
>  > switching the RS485 pins together) has caused a pulse anyway while
> ints
>  > were disabled, and this has not yet been cleared.
>  >
>  > Al
>  >
>  > Richard wrote:
>  >
>  > >
>  > > I am driving a 485 transceiver (SN65HVD10) with the LPC2104.  The
>  > > RE/ and DE lines are tied together and to a GPIO pin for
> direction
>  > > selection.  My problem is that when I enable transmission the
> bus is
>  > > driven low and a pulse is seen at my RXD input causing an
>  > > interrupt.  I have tried disabling the UART1 interrupt before I
>  > > toggle the direction pins of the 485 transceiver but the receive
>  > > interrupt fires off as soon as I enable the UART interrupts
> again.
>  > > Tying the direction pins of the tranceiver results in a race
>  > > condition so I have added a small delay to let the pins settle.
>  > >
>  > > Thanks for the help
>  > >
>  > > Richard
>  > >
>  > >
>  > >
>  > >
>  > >
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