G120HDR and EMX board CAN communication at 1000 K

NETMF & Gadgeteer
1

I have a test setup where i have a G120HDR communication with a EMX board over CAN. Everythings work smooth at 125 / 250 / 500 kb but at 1000 kb it starts spawning buss off errors on both devices.

Bitrate settings at the G120:
125: BRP = 20 T1 = 15 T2 = 8 -> ok on the CAN analyzer
250: BRP = 10 T1 = 15 T2 = 8 -> ok on the CAN analyzer
500: BRP = 5 T1 = 15 T2 = 8 -> ok on the CAN analyzer
1000: BRP = 2 T1 = 15 T2 = 8 -> Error on the CAN analyzer

On the EMX :
125: BRP = 24 T1 = 15 T2 = 8 -> ok on the CAN analyzer
250: BRP = 12 T1 = 15 T2 = 8 -> ok on the CAN analyzer
500: BRP = 6 T1 = 15 T2 = 8 -> ok on the CAN analyzer
1000: BRP = 3 T1 = 15 T2 = 8 -> ok on the CAN analyzer

Anyone is actually using the G120 CAN communication at 1000 Kb? and what bitrate settings?

2

Hi David,

I have not done any CAN with these modules yet but what is the sampling point set at with these bit rates?

I had a big issue getting a Cortex M0 processor to talk to an Atmel AT90CAN device and the issue was the sampling point and time quanta out of sync.

Dave…

3

I have to check values at work but should be approx 50%
one thing puzzles me the prescaler value 2 while i would think 2.5 is Correct, reading the nxp datasheets tonight to understand what could be involved.