Lpc2000

I saw a previous post that stated that the LPC2xxx can reach
115200kbps without modification, How do you do this? I can't seem to
get the data right at 115200

That's a tough one.  You can run 115200 without problems as long as
you have a crystal that supports standard baudrates, e.g. 14.756 MHz.
 Unfortunately this would not work with CAN any more. If you use a
crystal such as 12 MHz and run the CPU at 60 MHz, the CAN can go 1
Mbit/s or fractions thereof.
With 60 MHz you can approach 115200 to approx. 2% offset which will
work. So, while you will not hit 115200 exactly you can hit something
like 117500 (did not calculate it exactly) and this will work with a PC.

hth, Bob

another hint, you need to run VPB without divider otherwise it might
not work any more.

--- In lpc2000@yahoogroups.com, "SR" <emddjava@y...> wrote:

> I saw a previous post that stated that the LPC2xxx can reach
> 115200kbps without modification, How do you do this? I can't seem to
> get the data right at 115200

--- In lpc2000@yahoogroups.com, "SR" <emddjava@y...> wrote:
> I saw a previous post that stated that the LPC2xxx can reach
> 115200kbps without modification, How do you do this? I can't seem to
> get the data right at 115200

ok...You MUST do the following:
1.  In general, you MUST design in your main clock crystal to be some 
multipe of 9600. Personally, I use 11.0592Mhz, 14.7456Mhz and 22.
1184Mhz.

2.  Most PC UARTs can accept small variances from the 9600/schema, but 
in general, it is not a good idea to do this!

3.  Next, you MUST get your UART device driver fully operational at 
9600 baud, or some slow reliable baud rate...then later, kick the 
thing up to 115200

I am currently using an LPC2214 on several projects with 115200, and 
the thing seems to be working fine.

I also, have written a full interrupt-driven service routine. At these 
115200 speeds, it is a good idea to make your service as 
time-efficient as possible...Plus it is a VERY good idea to enable 
those 16-deep FIFOs when operating at 115200 baud

Ken Wada

Ken

the difference between the 2214 you are using and the 2294 the
question was about are 4 CAN interfaces.  CAN works at baudrates like
1 Mbit/s 500 kbit/s, 250 kbit/s..  you get the message.  While CAN is
highly dependend on the accuracy of the clock the UART can be off by
2.5 % and that is nothing about a good or bad idea, it is just how
much both, sender and receiver can be off and still get a valid
message across.

So, 11.059 or similar crystals can not work with CAN unless a very
powerful PLL would be implemented.

As mentioned in my previous post, it is possible to run 115200 from 60
MHz, in particulat when talking to a PC which is usually very accurate
with the baudrate.

Hope this help clarifying the issue, Bob

--- In lpc2000@yahoogroups.com, "Ken Wada" <kwada@a...> wrote:

> --- In lpc2000@yahoogroups.com, "SR" <emddjava@y...> wrote:
> > I saw a previous post that stated that the LPC2xxx can reach
> > 115200kbps without modification, How do you do this? I can't seem to
> > get the data right at 115200
> 
> ok...You MUST do the following:
> 1.  In general, you MUST design in your main clock crystal to be some 
> multipe of 9600. Personally, I use 11.0592Mhz, 14.7456Mhz and 22.
> 1184Mhz.
> 
> 2.  Most PC UARTs can accept small variances from the 9600/schema, but 
> in general, it is not a good idea to do this!
> 
> 3.  Next, you MUST get your UART device driver fully operational at 
> 9600 baud, or some slow reliable baud rate...then later, kick the 
> thing up to 115200
> 
> I am currently using an LPC2214 on several projects with 115200, and 
> the thing seems to be working fine.
> 
> I also, have written a full interrupt-driven service routine. At these 
> 115200 speeds, it is a good idea to make your service as 
> time-efficient as possible...Plus it is a VERY good idea to enable 
> those 16-deep FIFOs when operating at 115200 baud
> 
> Ken Wada

You are quite right about most terminals being able to communicate 
while being 2-3% off.

However, I have run into many IBM-PC clones that cannot communicate 
very reliably unless the baud rate is exact. The PC-clone industry is 
all over the map on this one.

I do not know about CAN or the CAN bus. So, therefore, I must accept 
what you say as the truth.

If this is so, then the user MUST supply the correct frequencies for 
the proper CAN operation, and then scrounge around to find a PC, or 
terminal that can tolerate the slightly-off baud rate.

Ken Wada

--- In lpc2000@yahoogroups.com, "lpc2100_fan" <lpc2100_fan@y...> 
wrote:
> Ken
> 
> the difference between the 2214 you are using and the 2294 the
> question was about are 4 CAN interfaces.  CAN works at baudrates 
like
> 1 Mbit/s 500 kbit/s, 250 kbit/s..  you get the message.  While CAN 
is
> highly dependend on the accuracy of the clock the UART can be off by
> 2.5 % and that is nothing about a good or bad idea, it is just how
> much both, sender and receiver can be off and still get a valid
> message across.
> 
> So, 11.059 or similar crystals can not work with CAN unless a very
> powerful PLL would be implemented.
> 
> As mentioned in my previous post, it is possible to run 115200 from 
60
> MHz, in particulat when talking to a PC which is usually very 
accurate
> with the baudrate.
> 
> Hope this help clarifying the issue, Bob
> 
> --- In lpc2000@yahoogroups.com, "Ken Wada" <kwada@a...> wrote:
> > --- In lpc2000@yahoogroups.com, "SR" <emddjava@y...> wrote:
> > > I saw a previous post that stated that the LPC2xxx can reach
> > > 115200kbps without modification, How do you do this? I can't 
seem to
> > > get the data right at 115200
> > 
> > ok...You MUST do the following:
> > 1.  In general, you MUST design in your main clock crystal to be 
some 
> > multipe of 9600. Personally, I use 11.0592Mhz, 14.7456Mhz and 22.
> > 1184Mhz.
> > 
> > 2.  Most PC UARTs can accept small variances from the 9600/schema, 
but 
> > in general, it is not a good idea to do this!
> > 
> > 3.  Next, you MUST get your UART device driver fully operational 
at 
> > 9600 baud, or some slow reliable baud rate...then later, kick the 
> > thing up to 115200
> > 
> > I am currently using an LPC2214 on several projects with 115200, 
and 
> > the thing seems to be working fine.
> > 
> > I also, have written a full interrupt-driven service routine. At 
these 

> > 115200 speeds, it is a good idea to make your service as 
> > time-efficient as possible...Plus it is a VERY good idea to enable 
> > those 16-deep FIFOs when operating at 115200 baud
> > 
> > Ken Wada