LAUNCHXL-F28379D: How to correctly calculate CAN bit rate

Alessandro Fano

Part Number: LAUNCHXL-F28379D
Other Parts Discussed in Thread: C2000WARE

Hello,

I've been working on the CAN of the F28379D for quite a while and I was wondering how to correctly set the parameters of the CAN_setBitRate(uint32_t base, uint32_t clock, uint32_t bitRate, uint16_t bitTime) function in order to obtain a bitrate of 1000 kb/s. I tried to set 1000000 as the bitRate parameters but this didn't change anything: I use a Kvaser Blackbird V2 as can sniffer and it only receives messages at 500 kb/s

I looked in the Technical Reference Manual but it wasn't really helpful, all I understood is that the function CAN_setBitTiming is to be used to obtain a control on the bit timing, but then again I have no clue on how to set the correct parameters.

Thanks in advance for your help,

Alessandro

over 4 years ago

0 Hareesh Janakiraman over 4 years ago

TI__Guru* 95315 points

Alessandro,

Please download my Application report http://www.ti.com/lit/sprace5. I have clearly explained how to compute the bit-rate. I strongly urge you to look at the Debug tips provided. Most CAN issues can be resolved by going through this checklist.

Application report http://www.ti.com/lit/spracq3 depicts lot of easy to understand waveforms and also provide a tool to introduce error at a chosen bit location.

The TRM chapter explains the CAN protocol implementation in the MCU. i.e. it explains the function of registers/bits. However, it does not explain the protocol itself. For protocol information, refer to these excellent videos:

https://training.ti.com/ti-precision-labs-canlinsbc-can-and-can-fd-protocol?context=1139747-1138099-1139707-1138111

https://training.ti.com/ti-precision-labs-canlinsbc-can-and-can-fd-overview?context=1139747-1138099-1139707-1138109

https://training.ti.com/ti-precision-labs-canlinsbc-can-physical-layer?context=1139747-1138099-1139707-1138110

Please try the can_ex4_simple_transmit.c project in C:\ti\c2000\C2000Ware_3_03_00_00\driverlib\f2837xd\examples\cpu1\can. It is a tested example and should work.

If you are running the C2000ware examples, they were written for ControlCard which has 20 MHz i/p clock. Launchpad has 10 MHz. You should ensure the project uses the correct clock setting. Go to the project properties in CCS, Build->C2000 Compiler->Predefined Symbols, in the Pre-define box, add the _LAUNCHXL_F28379D. That would take care of the i/p clock. Also bear in mind that the Launchpad has pinned out CAN-B (not CAN-A) and it uses GPIO12 for CANTXB & GPIO17 for CANRXB.

0 Alessandro Fano over 4 years ago in reply to Hareesh Janakiraman

Intellectual 270 points

Hello Hareesh, thank you for your answer.

I will try this as soon as I can.

Hareesh Janakiraman said:
If you are running the C2000ware examples, they were written for ControlCard which has 20 MHz i/p clock. Launchpad has 10 MHz. You should ensure the project uses the correct clock setting. Go to the project properties in CCS, Build->C2000 Compiler->Predefined Symbols, in the Pre-define box, add the _LAUNCHXL_F28379D. That would take care of the i/p clock. Also bear in mind that the Launchpad has pinned out CAN-B (not CAN-A) and it uses GPIO12 for CANTXB & GPIO17 for CANRXB.

Should I do this for both configuration CPU1_RAM and CPU1_FLASH?

Regards,

Alessandro

0 Hareesh Janakiraman over 4 years ago in reply to Alessandro Fano

TI__Guru* 95315 points

Clock configuration is independent of whether you run the code out of Flash or RAM. So, if you run the code on ControlCard, you have to do this.

C2000™︎ microcontrollers

C2000 microcontrollers forum

LAUNCHXL-F28379D: How to correctly calculate CAN bit rate