TMS320F28384S: Using aux clkin

luca mattonai

Part Number: TMS320F28384S
Other Parts Discussed in Thread: C2000WARE

Tool/software:

I have two osclillator one 14.7456Mhz that drives the SYSPLL to obtain 199.065.600Hz for the C28. The other is 50MHz and is connected to GPIO133, I would like use this oscillator to drive the AUXPLL to obtain 125MHz for the CM.

I modify the f2838x_sysctrl.c as below:

//
// Multipliers and dividers to configure 199.0656MHz SYSPLL output from 14.7456MHz XTAL
//
#define SYS_IMULT IMULT_27
#define SYS_REFDIV REFDIV_1
#define SYS_ODIV ODIV_2
#define SYS_DIV PLLCLK_BY_1

//
// Multipliers and dividers to configure 125MHz AUXPLL output from 50MHz XTAL
//
#define AUX_IMULT IMULT_40
#define AUX_REFDIV REFDIV_4
#define AUX_ODIV ODIV_4
#define AUX_DIV AUXPLLRAWCLK_BY_1
#endif

but the AUXPLL fail ti setup since the IsPLLValid fails since it was not possible to use the auxclkin in the DccRegs->DCCCLKSRC0 register.

Best regards

9 months ago

0 Ozino Odharo 9 months ago

TI__Mastermind 21085 points

Hi Luca,

Can you double check your AUXPLL setup. Here's a forum post that guide a user how to set up the CM clock frequency.

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1411595/tms320f28388d-setting-up-cm-clock-frequency

Regards,

Ozino

0 luca mattonai 9 months ago in reply to Ozino Odharo

Intellectual 690 points

Hi Ozino

In the post I don't find any reference to the aux clkin (GPIO133) and how to use it for the AUXPLL. I think the PLL lock correctly but there will be an error in the IsPLLValid procedure since is not possible to use the auxclkin as reference in the DCC.

Regards

0 Ozino Odharo 8 months ago in reply to luca mattonai

TI__Mastermind 21085 points

HI Luca,

I'm having your post routed to a clocking expert who would be better suited to help set up the auxiliary clock. Thank you for your patience.

Regards,

Ozino

0 Stevan Duraskovic 8 months ago in reply to luca mattonai

TI__Expert 4290 points

Hello,

I will look into this and get back to you.

0 Stevan Duraskovic 8 months ago in reply to luca mattonai

TI__Expert 4290 points

Hi Luca,

Please check TMS320F2838x TRM Chapter 3.7.6 PLL/AUXPLL. It provides you with the equation to configure these. The dividers seem to be set to wrong values. https://www.ti.com/lit/ug/spruii0f/spruii0f.pdf

0 luca mattonai 8 months ago in reply to Stevan Duraskovic

Intellectual 690 points

Hi Stevan

I don't think the problem is in parameters, but if you look at the AuxPll setup code you will see that the procedure will call the IsPLLValid procedure but when

the procedure select the source for select the reference clock it fails since it is no possible to use the auxclkin as reference and switch just fall in default case.

//
// Configure Clock Source0 to whatever is set as a reference
// clock source for PLL
//
// Clk Src0 Key 0xA to enable clock source selection
//
switch(oscSource)
{
case INT_OSC1:
DccRegs->DCCCLKSRC0.all = 0xA001; // Clk Src0 = INTOSC1
break;

case INT_OSC2:
DccRegs->DCCCLKSRC0.all = 0xA002; // Clk Src0 = INTOSC2
break;

case XTAL_OSC:
case XTAL_OSC_SE:
DccRegs->DCCCLKSRC0.all = 0xA000; // Clk Src0 = XTAL
break;

default:
//
// Code shouldn't reach here
//
break;
}

the procedure return false and the aux pll is not programmed.

Best regards

Luca

0 Stevan Duraskovic 8 months ago in reply to luca mattonai

TI__Expert 4290 points

Did you go through TRM clocking section or examples in C2000Ware to compare any differences?

0 luca mattonai 7 months ago in reply to Stevan Duraskovic

Intellectual 690 points

Hi Stevan

I read TRM and program the AUXPLL as I want, but to do so I have to comment out the call to IsPLLValid. Did you try to get an empty project for the 2838x and set the AUXPLL for use AUXCLKIN? If yuo step into the set auxpll code you will undestand what appens.

There are no example that use the auxclkin.

Best Regards

+1 Prarthan Bhatt 7 months ago in reply to luca mattonai

TI__Genius 13715 points

Luca,

In case you wan to use AUXCLKIN as source with DCC enabled, please refer to the TRM note below :

Alternately if you dont like to change the driverlib function, you can select INTOSC1 as clock source for counter 0 (src0) and AUXPLL as DCC clk src1. Since your AUXCLKIN goes to AUXPLL monitoring the output of AUXPLL should be sufficient.

The issue you are seeing seems to be an issue with the values passed to SysCtl_isPLLValid() function, currently the way its called in SysCtl_setAuxClock would not work with AUXCLKIN. I would suggest modify that to pass INTOSC1 to the second arg highlighted below

Thanks

+1 luca mattonai 7 months ago in reply to Prarthan Bhatt

Intellectual 690 points

thanks Prathan

I understand

Best Regards

0 luca mattonai 7 months ago in reply to luca mattonai

Intellectual 690 points

Hi Prathan

I'm not using driverlib and I want to set auxpll rewriting the InitAuxPll function in f2838x_sysctrl.c, and I write the following function:

and I call with the following parameters:

set_aux_pll(REFDIV_2, IMULT_16, ODIV_4);

I have a 50MHz oscillator connected to AUXCLKIN (GPIO133) so I want a AUXPLL frequncy of 100MHz to use for CM and Timer 2 that I have to use as timetag in the application (20us).

But if I measure the Timer 2 freq using Timer 0 every 1ms I get a strange result. Can you Help me?

Best Regards Luca

0 Prarthan Bhatt 7 months ago in reply to luca mattonai

TI__Genius 13715 points

Hi,

Are you selecting AUXPLLCLK as source for Timer2 clock ?

Can you configure AUXPLLCLK to XCLKOUT and monitor clock frequency on GPIO using scope ?

Thanks

+1 luca mattonai 7 months ago in reply to Prarthan Bhatt

Intellectual 690 points

Hi Prarthan

The auxpll was programmed correctly the problem was that SYSCLK at 176MHz was not greatre then the double of 100MHz and timer 2 don't sample correctly, I solve using a prescaler of 2.

Best Regards

Luca

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TMS320F28384S: Using aux clkin