Is there any way to control the speed of DAC or to modify the speed of the AnalogOut?

Questions » Is there any way to control the speed of DAC or to modify the speed of the AnalogOut?

10 years, 8 months ago.

Please if anybody can, send mi some code that can increase the speed of the DAC. Thanks in advance

1 Answer

10 years, 8 months ago.

Dear Rolando-san,

I have tried similar thing please check my funcgen

https://developer.mbed.org/users/Rhyme/code/funcgen/

Although I have tested this only with FRDM-KL25Z, as analog out is same PTE30, it may work with FRDM-KL46Z.

Please let me know if it works ok on your board.

IMHO, we can not make DAC faster, but we can make it look slower, in my case with FRDM-KL25Z, I could make the timer interval as fast as 25us and logically there won't be any limit for the slower interval.

Best Regards, 14-Jan-2015 moto

Dear Motoo

Thanks very very much for your answer and for to send me your hard and important

works that I'll see, study and probe with my FRDM-KL-46Z, sending you the results . Please, if it's possible I wish that you send me your e-mail for comunicate us more

directly; this is mine; 'rolandosr013@hotmail.com'.This is my code for a DAC too fast, but

with it I havent'n results(nothing appear in PTE30 and I do'nt know were is

'DACREF_1.!!!), please analyze it you and tell me whats strong.

Regards and thanks in advance dear friend!.

FastAnalogOut

include "mbed.h"
include "clk_freqs.h"

define MAX_FADC 6000000
define CHANNELS_A_SHIFT 5
define SIM_SCGC6_DAC0_MASK 0x80000000u
define DAC_DATH_DATA0_MASK 0xF

ifdef TARGET_K20D50M static const PinMap PinMap_DAC[] = { {PTE30, DAC_0,STM_PIN_DATA(STM_MODE_ANALOG, GPIO_NOPULL, 0}),DAC out {NC, NC, 0} };
endif

void inicio(PinName , bool); void enable(bool enabled = true); void disable( void ); void write (uint16_t ); char DACnumber; bool enabled;

uint16_t LH=0;

int main(){

inicio(PTE30, true);

while(1) {

LH = LH++; enable(true); write(LH); wait(0.1); if(LH == 100) { LH = 0; } } }

void inicio(PinName pin, bool enabled){

DACnumber = (DACName)pinmap_peripheral(pin, PinMap_DAC);

if (DACnumber == (DACName)NC) { error("DAC pin mapeado fallido"); }

SIM->SCGC6 |= SIM_SCGC6_DAC0_MASK;

SIM->SCGC5 |= 0x2000;

uint32_t PCLK = bus_frequency(); uint32_t clkdiv; for (clkdiv = 0; clkdiv < 4; clkdiv++) { if ((PCLK >> clkdiv) <= MAX_FADC) break; } if (clkdiv == 4) clkdiv = 0x7;

pinmap_pinout(pin, PinMap_DAC);

enable(enabled);

}

void enable(bool enabled){

if(enabled) { DAC0->C0 |= DAC_C0_DACEN_MASK ; }else disable();

}

void disable( void ) { if (!enabled) { DAC0->C0 &= DAC_C0_DACEN_MASK; } }

void write (uint16_t valor) { DAC0-> DAT[1].DATL &= 0x00; DAC0-> DAT[1].DATH &= 0x00; uint16_t temp= valor;

DAC0-> DAT[1].DATL |= (valor & 0xFF); DAC0-> DAT[1].DATH |= ((temp>>8)& 0xF);

temp=0;

Serial tt(USBTX,USBRX); tt.printf("DATL %d, DATH= %d ", DAC0-> DAT[1].DATL, DAC0-> DAT[1].DATH);

}

posted by Rolando RERIANI 14 Jan 2015

I have just tried my funcgen program with FRDM-KL46Z.

Without any modification, except switching the platform from FRDM-KL25Z to FRDM-KL46Z, it worked fine!

I think this is the virtue of "mbed".

With FRDM-KL46Z, my program could generate up to 13300Hz,
but when freq hit 13350 Hz, output stayed as DC level.

To make it simple, I have just hacked a sample program.
Following program is generating about 40Hz saw wave on my FRDM-KL46Z now.

#include "mbed.h"

DigitalOut led(LED_RED);

int sample_time = 25 ; 
AnalogOut aout(PTE30) ;
Ticker *timer ;

#define DAC_MAX 1.0
#define DAC_MIN 0.0
float dac_value = 0.0 ;
float dac_delta = 0.001 ;

void tick_time(void)
{
    aout = dac_value ;
    dac_value += dac_delta ;
    if (dac_value >= DAC_MAX) {
        dac_value = DAC_MIN ;
    }
}

int main()
{
    timer = new Ticker() ;
    timer->attach_us(&tick_time, sample_time) ;
    
    while (true) {
        led = !led; // toggle led
        wait(0.2f);
    }
}

posted by Motoo Tanaka 14 Jan 2015

Rolando RERIANI

Important changes to forums and questions

10 years, 8 months ago.