CAN Bus at 100Kbps bitrate?

NETMF & Gadgeteer
1

I know how setup my FEZ for 125Kbps and 250Kbps bitrates ,because I have readed in the manual that the values are 24 and 12 in BRP, but if I need 100Kbps what is the value for the BRP and how can I calculate it ??

// CLK = 72 Mhz, with BRP = 24 -> 3Mhz CAN clock
// 3Mhz/125Kbps = 24 TQ
// T1 = 15
// T2 = 8

// CLK = 72 Mhz, with BRP = 12 -> 6Mhz CAN clock
// 6Mhz/250Kbps = 24 TQ
// T1 = 15
// T2 = 8

Thank you,

2

Please find CAN tutorial on this page Support – GHI Electronics

Welcome to the community

3

I have readed the CAN tutorial, but I don’t know what are the values I have to use for BRP and CAN clock.

I use this web http://www.kvaser.com/en/support/bit-timing-calculator.html to get T1 and T2 with
[Input clock frequency (MHz)]: 72 and [Desired CAN bus bit rate (kbps)]: 100

This is the configuration that I’m using , but it doesn’t work properly.

// Bitrate  100Kbps
// CLK = 72 Mhz, with BRP = 30 -> 2.4 Mhz CAN clock
// 2.4Mhz/100Kpbs = 24 TQ
// T1 = 16;
// T2 = 8;
// Sync = 1;

Don’t know what I’m doing wrong???

Kind Regards.

4

A BRP value of 30 is correct for 100 kbit/s, but T1 and T2 should have the same values in this case as in the examples for 125 kbit/s and 250 kbit/s as we are using the prescaler (BRP) to scale the data rate.

Thus use “T1=15” instead of “T=16”.