Lpc2000

The Keil examples do indeed work right.  The following:
#define CANBit125k_60MHz 0x25C02F // 0+1 5+1 2+1 3+1 70 47+1
also works right.  He has changed the sampling intervals which is 
why it looks so "wrong".  His comment with all those magic numbers 
is a note about it.
James



--- In lpc2000@yahoogroups.com, Greg Deuerling <egads@f...> wrote:
> 
> See post below for full text I'm replying to...
> 
> From: dietmar_wengler [mailto:dietmar_wengler@y...] 
> Sent: Saturday, March 05, 2005 4:17 PM
> To: lpc2000@yahoogroups.com
> Subject: [lpc2000] Re: CAN baudrate setting
> 
> > Please download the Keil Examples for a CAN Driver, that was
> > very helpful for me:
> > http://www.keil.com/download/docs/lpc2_can_examples.zip.asp
> 
> I have the files from the Keil link above, but it does not 
match/jive with
> what you have posted.
> 
> The CANALL source code has the following define:
> 
> // Common CAN bit rates
> #define   CANBitrate125k_12MHz   0x001C001D
> #define   CANBitrate250k_12MHz   0x001C000E
> 
> I've ran CANALL on my LPC2194 design and on Keil's MCB2100 and the 
above
> numbers work fine.  Both boards have a 12Mhz crystal, 60Mhz 
internal
> clock, VPDIV=1;
> 
> You say:
> 
> #define CANBit125k_60MHz  0x25C02F // 0+1  5+1   2+1  3+1 70   47+1
> #define CANBit250k_60MHz  0x25C017 // 0+1  5+1   2+1  3+1 70   23+1
> 
> Those are WAY off from what I know to work.
> Am I missing something?
> 
> Greg Deuerling
> Fermi National Accelerator Laboratory
> Feynman Computing Center, Room 370, MS 368
> P.O.Box 500 Batavia, IL 60510
> (630)840-4629     FAX  (630)840-5406
> Electronic Systems Engineering Group
> Work: egads@f...
> Personal: gdeuerling@c...
> 
>   
> ________________________________________
> From: dietmar_wengler [mailto:dietmar_wengler@y...] 
> Sent: Saturday, March 05, 2005 4:17 PM
> To: lpc2000@yahoogroups.com
> Subject: [lpc2000] Re: CAN baudrate setting
> 
> 
> Hi Mouaaz,
> 
> the Rules of Bit Timing Parameters are not described in the 
Philips 
> LPC2000 User Manuals. And they are not easy. Please refer to the 
> Bosch Homepage for more Information.
> But, I give you an Example that works very well in my application:
> 
> Assumed that you setup the PLL and the cclk = 60 MHz and the VPB 
> Divider = 4 (after RESET) and the pclk = 15 MHz, you can use the 
> following parameters for a first test:
> 
> // Common CAN bit rates for cclk=60 MHz, VPBDIV=4: ==> pclk=15 MHz:
> // CAN Bit Timings in Detail -->   // SAM TSEG1 TSEG2 SJW SP%  BRP
> #define CANBit10k_15MHz   0x25C095 // 0+1  5+1   2+1  3+1 70  149+1
> #define CANBit25k_15MHz   0x25C03B // 0+1  5+1   2+1  3+1 70   59+1
> #define CANBit50k_15MHz   0x25C01D // 0+1  5+1   2+1  3+1 70   29+1
> #define CANBit100k_15MHz  0x25C00E // 0+1  5+1   2+1  3+1 70   14+1
> #define CANBit125k_15MHz  0x25C00B // 0+1  5+1   2+1  3+1 70   11+1
> #define CANBit250k_15MHz  0x25C005 // 0+1  5+1   2+1  3+1 70    5+1
> #define CANBit500k_15MHz  0x25C002 // 0+1  5+1   2+1  3+1 70    2+1
> #define CANBit1000k_15MHz 0x48C000 // 0+1  8+1   4+1  3+1 67    0+1
> 
> The following parameters for VPBDIV = 1 I have calculated on this 
> base:
> 
> For cclk = 60 MHz and VPBDIV = 1, the following parameters should 
> work:
> 
> // Common CAN bit rates for cclk=60 MHz, VPBDIV=1: ==> pclk=60 MHz:
> // CAN Bit Timings in Detail -->   // SAM TSEG1 TSEG2 SJW SP%  BRP
> #define CANBit10k_60MHz   0x25C257 // 0+1  5+1   2+1  3+1 70  599+1
> #define CANBit25k_60MHz   0x25C0EF // 0+1  5+1   2+1  3+1 70  239+1
> #define CANBit50k_60MHz   0x25C077 // 0+1  5+1   2+1  3+1 70  119+1
> #define CANBit100k_60MHz  0x25C03B // 0+1  5+1   2+1  3+1 70   59+1
> #define CANBit125k_60MHz  0x25C02F // 0+1  5+1   2+1  3+1 70   47+1
> #define CANBit250k_60MHz  0x25C017 // 0+1  5+1   2+1  3+1 70   23+1
> #define CANBit500k_60MHz  0x25C00B // 0+1  5+1   2+1  3+1 70   11+1
> #define CANBit1000k_60MHz 0x48C003 // 0+1  8+1   4+1  3+1 67    3+1
> 
> Write this Values to the CANBTR Register.
> 
> The defined CAN Bit Rates works very well in my application (Keil 
> MCB2100 connected to a CAN Analyzer (CANalyzer from vector 
> informatik)).
> 
> The right Bit Rate Calculation is:
> 
> Bit rate = cclk / ( VPBDIV * BRP * ( TSEG1+1 + 1 + TSEG2+1))
> 
> The Sample Point should be in the Range 50% to 90 %.
> 
> Please download the Keil Examples for a CAN Driver, that was very 
> helpful for me:
> 
> http://www.keil.com/download/docs/lpc2_can_examples.zip.asp
> 
> Greetings from Dietmar.
> 
> http://www.weiss-electronic.de
> 
> -----------------------------------------------------------------
> 
> --- In lpc2000@yahoogroups.com, "mouaaz" <mouaaz@y...> wrote:
> > 
> > Dear all,
> > 
> > I am using two LPC2129 boards having 12 MHz clock, with CCLK and 
> PCLK
> > set to 60 MHz. They are connected via a CAN link. I am trying to 
set
> > the bus timing register C1BTR to run the CAN at the baudrate of 1
> > Mbit/s. The value I tried is :
> > 
> > C1BTR = 0x34C005;
> > 
> > But it did not work.
> > 
> > Anybody can help me to work out the correct setting of this 
register
> > to let the CAN go for 1 Mbaud.
> > 
> > Thanks very much.
> > 
> > Mouaaz
> > 
> > PS. the correct setting for 125 kbaud was: C1BTR = 0x001C001D;
> 
> 
> 
> 
> 
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