topic Re: CAN bus - can_message_t .cs - Code and Status in S32 SDK

CAN bus - can_message_t .cs - Code and Status

vagabond — Wed, 24 Oct 2018 00:59:04 GMT

Hi guys,

Does anyone know what exactly is the .cs field in can_message_t struct represents?

Struct is defined as below, and I can't find a clear definition, except "Code and Status"

typedef struct {
uint32_t cs; /*!< Code and Status*/
uint32_t id; /*!< ID of the message */
uint8_t data[64]; /*!< Data bytes of the CAN message*/
uint8_t length; /*!< Length of payload in bytes */
} can_message_t;

I'm using a S32K144 EVB and a USB-CAN interface.I'm sending data from the USB-CAN interface to the SK32K144 board.

Everything works fine, but when I am receiving data from the CAN bus, this ".cs" value changes every time, apparently random, even if the data sent from the CAN adapter is the same.

Re: CAN bus - can_message_t .cs - Code and Status

alexandrunan — Wed, 24 Oct 2018 11:32:59 GMT

That fileld represents the code and status of the message buffer, you can read his description in the Chip RM "Message buffer structure" in FlexCAN module description chapter.

It encodes more fields and one of them is a Time STAMP filed "This 16-bit field is a copy of the Free-Running Timer, captured for Tx and Rx frames at the time when the beginning of the Identifier field appears on the CAN bus." This is way every time have a different value/ random see as you mention.

Re: CAN bus - can_message_t .cs - Code and Status

vagabond — Wed, 24 Oct 2018 16:56:11 GMT

Thanks a lot Alexandru, it's clear now.

Found the complete description in the reference manual at

https://www.nxp.com/docs/en/reference-manual/S32K-RM.pdf

page 1718 :smileyhappy: