Lpc2000

--- In lpc2000@yahoogroups.com, Duke Whisky <duke.whisky@...> wrote:
>
> Hello,
> 
> There is a simple tip to generate the 13-bit break without having to
implement 
> external glue logic. The LIN bus operates at know (an relatively low) 
> bitrates.
> 
> The idea is to change the value of the prescaler that defines the
baudrate in 
> the UART. You can calculate a "virtual" baudrate that make an
eight-bit long 
> 0x00 byte as long as 13-bits at the nominal LIN bus bitrate. 
> 
> After the break has been sent, you can switch back to the normal
prescaler 
> value for the LIN bus speed and go on with the rest of the frame. I
Haven't 
> checked if the prescaler settings possible with an LPC2129 allow
this with 
> enough accuracy to mach the constraints of the LIN spec, but I think it 
> should work.
> 
> This  was used in the very first implementations of the LIN
protocol, when 
> LIN-compliant UARTs (like in the 16F690) were not yet available. I
Remember 
> examples in old appnotes from Infineon on their C167 controller.
Probably 
> this is still available on their website.
> 
> Hope this can save extra hardware ... which represents money !!
> 
> Regards
> 
> "Duke"

That is a very clever solution!  I am not concerned about LIN but
there is an awkward start condition for the DMX protocol used for
stage lighting.  I'll have to remember this.

Thanks
Richard