SPC560D CAN baudrate confirmation

[AndreasPA]

Hello all,

im working on a project that uses an SBC, using my logic analyser i can confirm data is coming and and looks to be a can signal but it seems my baud rate timing is incorrect or something else is amiss.

my board is the SPC560DL1, i understand the the flexcan uses Perphial set 2 clock so mine by default is set to 24Mhz.

i've attached images of my settings and results

http://www.bittiming.can-wiki.info/#Freescale

here is the table i've created with < 24Mhz, 75% sample point >

 

my settings for 250 are

sample point @ 75%, i've also tried 87.5

Pclk 24Mhz

propseg= 2

pseg1 =7

pseg2 =3

presdiv =6

which should solve to 24,000,000/6 = 4000000

4000000/16 = 250 baud

 

Here is my code snippit that i'm using to test can functionality

data on my output looks like this

with my analyer it's seeing garbage on the decoder side so im guessing the timing is incorrect

[Erwan YVIN]

Hello ,

According to your settings ,

the bitrate should be 250 Kbit/s

I do not see any timing or scale in your screenshot ...

Best regards

Erwan

[AndreasPA]

Hey Erwan,

here is an attached image, the data constantly changes along with everything else but here is one that had more data than the rest and with a timing marker as well.

Setup:

The actual id is 0x70

8 bytes of data where the message is 0F 00 00 00 00 00 00 0F

I've also attached the file with the entire can recording ( program is logic 2 from salaeae) , also added in the timing for the start and end.

 

[AndreasPA]

attached image of setup code, adjusted since the original post

[AndreasPA]

Here is also a setup using the mcp2551 with just 2 120 ohm resistors at each end

the data in this message should be different to the prior as this is on my spc560d-dis board

channel 2 and 3 are connected to TX and RX

Edit: had accidently marked vdd to be gnd

[AndreasPA]

Hey Erwan, i found out that beyond 20kbps the can signal becomes unstable.

i was told that i should be using the external clock to which i've tried enabling but when i do it results in a system reset.

is there a process to enabling the external clock ?

these also some boxes like enable clockout that i dont quite understand what it exactly does.

a guess would be that you would need to tick it along with the bypass clock but in doing that i still get an unexpected reset.

 

on my board i have the the CSTNE16M0V53C000R0 (16Mhz) which is advertised to be an alternative to the one used in the spc560d disc board.

[Giuseppe DI-GIORE · Accepted solution]

Hello,

the issue is in your configuration.

the formula to calculate the clock is:

PCLK / (PRESDIV + 1)

So, in your configuration PRESDIV has to be set to 5 (and not to 6)

Regards,

Giuseppe

[AndreasPA]

You are a livesaver!

To avoid this issue for anyone else, would it be possible to change or add in a note to the application configuration page ?