RM48 CAN Pins as GIO

stomp

Other Parts Discussed in Thread: RM48L952, HALCOGEN

Hi,

Working on some unit testing and need clarification on the use of GIO pins for the 3 DCAN modules on RM48L952.

To set the IO direction of the Tx pin we use:

//clear init bit
canREGx->CTL &= (0x00000001U ^ 0xFFFFFFFF);

//set the Transmit Pin to Output
canREGx->TIOC = 1U << 2U;

However this has no effect and we can not toggle the output by physically setting or clearing the bit as per:

//set
canREGx->TIOC |= (1U << 1U);

//clear
canREGx->TIOC &= ((1U << 1U) ^ 0xFFFFFFFF);

We have referred to the HalCoGen generated code (note: We don't use HalCoGen in our projects) and we find:

/** - Setup control register
*     - Enter initialization mode
*/
canREG2->CTL = 0x00000001U;
	
/** - CAN2 Port output values */
canREG2->TIOC =  (uint32)((uint32)1U  << 18U )
               | (uint32)((uint32)0U  << 17U )
               | (uint32)((uint32)0U  << 16U )  
               | (uint32)((uint32)0U  << 3U )  
               | (uint32)((uint32)1U  << 2U )    
               | (uint32)((uint32)1U << 1U );

So it seems HalCogen is setting the Init Bit = 1 in the control register, despite the note on section 23.17.29 ("The values of the IO Control registers are only writable if Init bit of CAN Control Register is Cleared.")

Could someone please confirm what is the correct method to enable the GIO functionality of a CAN pin, including the correct Control Register setting?

Thanks

Stomp!.

over 10 years ago

0 KARTHIKEYAN RAJAMANICKAM over 10 years ago

TI__Genius 11645 points

Stomp,

Will look in the Halcogen code and get back to you.

0 KARTHIKEYAN RAJAMANICKAM over 10 years ago in reply to KARTHIKEYAN RAJAMANICKAM

TI__Genius 11645 points

Stomp,

From my initial analysis, looks like there is a mistake in TRM.

It should ideally look like as shown below,

The values of the IO Control registers are only writable if Init bit of CAN Control Register is set.

I will re-confirm this soon once I get to talk with the documentation team.

0 stomp over 10 years ago in reply to KARTHIKEYAN RAJAMANICKAM

Genius 4675 points

Thanks Karthik,

Either way with the Init bit set or cleared makes no difference, I can not get the IO pins to function.

Thanks
Stomp!

0 KARTHIKEYAN RAJAMANICKAM over 10 years ago in reply to stomp

TI__Genius 11645 points

Stomp,

I see this discrepency only with RM48 so I have requested the concerned folks to have a look at it.

Let me spend sometime on the hardware and get back to you on this.

Sorry for the trouble.

0 KARTHIKEYAN RAJAMANICKAM over 10 years ago in reply to KARTHIKEYAN RAJAMANICKAM

TI__Genius 11645 points

Stomp,

I just tried the following sequence and it works fine for me.

By default Init bit is SET and I leave it as is.

Heading down to the I/O registers and I see both the I/O's are configured to be in Functional mode by default.

Change both the TX,RX I/O func bits to be in GIO mode, as well as TX pin Dir to be OUT and RX pin Dir to be INPUT.

With those pins looped back externally, I see the value that's forced on TX OUT reflecting with RX IN register.

Can you pls recheck this once with Init bit set ?

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RM48 CAN Pins as GIO