LAUNCHXL-F28379D: CAN clock source selection with TI examples

vincent liebart

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

Tool/software:

Hello,

I started CAN application from TI examples which include SysConfig. Everything works, but there is a detail I don not understand.

Where in the code is the source of the CAN clock selected ? This should be done in CLKSRCCTL2 register but

- it seems that clocktree.h, that SysConfig generates, does not affect this register. Anyway, TI examples does not use this file, but device.c

- it seems that Device_Init does not set this register.

So, is this selection set by its default value ? Which DriverLib function should I use to set the source of the CAN clock properly ?

Thank you in advance.

Vincent

over 1 year ago

+1 QJ Wang over 1 year ago

TI__Guru**** 194796 points

Hi Vincent,

The default clock source for CAN modules after reset is sysclk. If the clock source is net selected in the code, the default value is used.

In the example, the SYSCLK=200MHz, the Prescaler, SEG1, SEG2 are 15,15, and 7. SO the baudrate = 200MHz/(15+1)(15+1+7+1+1)=500Kbps.

vincent liebart said:
Which DriverLib function should I use to set the source of the CAN clock properly ?

CAN_selectClockSource(uint32_t base, CAN_ClockSource source); can be used to select clock source for CAN modules.

0 vincent liebart over 1 year ago in reply to QJ Wang

Intellectual 470 points

thank you.

I found odd that SysConfig does not generate the line CAN_selectClockSource(uint32_t base, CAN_ClockSource source) in board.c.

0 vincent liebart over 1 year ago in reply to QJ Wang

Intellectual 470 points

It might be a silly question but ... where in the code does SysConfig set up the bit rate ? I did not find any use of CAN_setBitRate function in the generated board.c file

+1 QJ Wang over 1 year ago in reply to vincent liebart

TI__Guru**** 194796 points

Hi Vincent,

main() --> Board_init() --> CAN_init() --> myCan0_init() --> CAN_setBitTiming((..)

+1 Sahil Deshpande over 1 year ago in reply to vincent liebart

TI__Expert 6035 points

Vincent,

The function CAN_setBitTiming() is called in board.c that is used to set up the bit rate. Sysconfig calculates the bit timing parameters itself, hence, does not need to call the CAN_setBitRate() function.

Thanks.

0 vincent liebart over 1 year ago in reply to Sahil Deshpande

Intellectual 470 points

Hello, thank you all. It s very clear for me now. I wanted to be sure that I will not have any problem in the future, due to a misunderstanding.

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LAUNCHXL-F28379D: CAN clock source selection with TI examples