TMS320F28377D: I am trying to sample less than 100ns.

Kang Andrew

Part Number: TMS320F28377D
Other Parts Discussed in Thread: ADC12DL040

Hello

It takes 248ns (4MHz) execution time.
We want less than 100ns (10MHz sampling).
All interrupts are disabled.
The external crystal is 20 MHz.
Is there any way to make it run faster?

under.
Is it possible to speed up using a function?
InitSysPll(XTAL_OSC,IMULT_20,FMULT_0,PLLCLK_BY_2);

under.
If the timer interrupt is set to 0.1us, it takes more than 500ns.
// ConfigCpuTimer(&CpuTimer0, 200, 0.1); // 10MHz (100ns)

Thanks.

*********************************************

over 2 years ago

0 Hareesh Janakiraman over 2 years ago

TI__Guru* 95315 points

I regret I am unable to understand exactly what your issue is and what help you are expecting from us. Also, debugging your code is not something we can support on the e2e forum. That being said, I will make an attempt to answer some questions.

Kang Andrew said:
Is it possible to speed up using a function?
InitSysPll(XTAL_OSC,IMULT_20,FMULT_0,PLLCLK_BY_2);

The rated maximum operating frequency of this device is 200 MHz. It cannot be operated beyond that speed.

The execution time depends on many factors such as clock speed, whether code is running from Flash or RAM and everything else going on in the application. Without a thorough knowledge of the application software, our ability to help with issues like this is very limited.

0 Kang Andrew over 2 years ago in reply to Hareesh Janakiraman

Prodigy 150 points

sorry.
My question was not specific.

I am trying to sample 10MHz (0.1us) using the EMI interface of an external ADC (ADC12DL040).

first try.
If I set the timer to 0.1us and collect data at 10MHz (0.1us), it takes 0.5us each. (Other interrputs are disabled)

ConnfigCpuTimer(&CpuTimer0, 200, 0.1); // 10MHz (0.1us)

second try.
in the main function
Even reading the external ADC, it takes about 0.248us each. (timer interrput is disabled)

#define ADCa 0x00300000 // for External ADC(ADC12DL040)
void main(void)
{

for(i = 0; i < 1024; i++)
{
GPIO_WritePin(MCU_TP2, 1); // TP16(GPIO99) Test Point
adc_tmpa=(*(Uint16*)(ADCa) & 0xffff);
GPIO_WritePin(MCU_TP2, 0); // TP16(GPIO99) Test Point
}

}

0 Hareesh Janakiraman over 2 years ago in reply to Kang Andrew

TI__Guru* 95315 points

Kang,

I presume you have interfaced the ADC12DL040 chip via EMIF. The time it takes to read the data is dependent on everything else going on in the system, not just the interrupts. This is too application-centric question, so our ability to help is limited.

You may want to look into www.ti.com/lit/SPRAC96 for helpful tips.

0 Kang Andrew over 2 years ago in reply to Hareesh Janakiraman

Prodigy 150 points

I plan to tet the exernal ADC using the DMA sample program(emif_dc_dma.c)

DMA related questions will be asked in another thread.

thank you

0 Kang Andrew over 2 years ago in reply to Kang Andrew

Prodigy 150 points

Even if I use DMA, 0.1us does not seem to be guaranteed.

So I am trying to convert it to assembly code.

Could you please convert the below to assembly code?

Thank you

**** External ADC sampling *******

#define ADCa 0x00100000 //emif1 addr

Uint16 adc_tmpa[1024] = {0, };

Uint i = 0;

while(i < 1024)
{
adc_tmpa[i++] = *(Uint16*)(ADCa); //ADC 1024ea : 256us (=1024ea * 250ns)
// adc_tmpa[i++] = __addr32_read_uint16(ADCa); //ADC 1024ea : 289us (=1024ea * 282ns)
}