TMS320F280040-Q1: SPI speed limit

Crane,

In F280040 device, Max SPI baud rate is LSPCLK / 4 (100 MHz / 4 = 25 MHz).

Where did you see the 6 MHz limitation?

Regards,

Manoj

Hi Manoj,

In spi.h, the comment on SPI_setConfig() function says.

//! - \e bitRate can be no greater than \e lspclkHz divided by 4.

lspclkHz is DEVICE_LSPCLK_FREQ 25MHz.

Regards,

Crane

Ok got it. It's good.

By the way, where is the device.h generated from? It is not from library, neither from sysconfig.

Hi Manoj,

I was working on something else and got to try this now.

If the value is changed in device.h, the statement below in device init would cause software interrupt:

ASSERT(SysCtl_getLowSpeedClock(DEVICE_OSCSRC_FREQ) == DEVICE_LSPCLK_FREQ);

I am not sure if it is relevant to that the value is not changed in SysConfig. 

Another question is, since device.h is genrated by SysConfig, does it have to be changed in SysConfig? If yes, where it is in SysConfig? 

Thanks!

Crane

Hi Manoj,

My version doesn't have clock tree. What might be missing?

Thanks!

Crane

Is this issue resolved? Can I close this thread?

Hi Manoj,

Still didn't see the clock tree.

Thanks!

Crane

I tried downloading the latest sysconfig myself. I don't see the problem and I do see clocktree icon. I selected the below software product. What are you selecting?

What is that? I have only below options:

It seems not C2000Ware SDK. 

Do you have the latest C2000Ware? If not, install latest C2000Ware.

No, I am using 4.2. The latest version I see is 4.3 at https://www.ti.com/tool/C2000WARE.

Hi Crane,

Did issue get resolve after installing latest C2000Ware ?  Manoj Santha Mohan is on leave and he will respond to your query before end of this week. 

Vivek Singh

Hi Vivek,

I've change the DEVICE_LSPCLK_FREQ to DEVICE_SYSCLK_FREQ / 1
as well changed the LOSPCP to /1 in the clock tree.

It appears that the ASSERT(SysCtl_getLowSpeedClock(DEVICE_OSCSRC_FREQ) == DEVICE_LSPCLK_FREQ);
condition fails because the clockOut (return value) from the SysCtl_getLowSpeedClock() function is still returning
25000000 which would only hold true if DEVICE_LSPCLK_FREQ == DEVICE_SYSCLK_FREQ / 4.

How can I get SysCtl_getLowSpeedClock(DEVICE_OSCSRC_FREQ) to give me a value of 100000000 or 50000000,
so I can use a higher SPI data rate?

Hi Crane,

Are you able to scope the clock on pin and see what is the frq ? I would also suggest to check the value of LOSPCP register in CCS register view to make sure if has correct value (as programmed in application).

Vivek Singh

Hi Vivek, 

the program will not run if it gets stuck at the assert so I cannot test the frequency with the changes. Without the changes the measured frequency is 6.25 Mhz. In both cases the LOSPCP register shows as 2. 

Yes, I installed the latest version of C2000Ware v4.3 and SysConfig 1.16. That's how the clock tree is available in SysConfig. Otherwise, I couldn't even see that.

Now I already configured the new device clock in clock tree and see the new DEVICE_LSPCLK_FREQ value in clocktree.h. But it is just not used in the project.

Thanks Manoj!

Mine looks different.

Might it be because I am using the sysconfig file is in a separate folder, not together with the project?

Yes, you need to invoke sysconfig from the project file. Please check any C2000Ware example for SPI. It shows you how to call the sysconfig from project file.