MCP4725 Generating a sine / triangle wave and controlling it

[DanMx93]

Hi, I hope someone can help me.
I'm using the DAC mcp4725 for generate triangle and sine waves and I have some questions.
How can I control the frequency of the wave I'm generating?
For example, I want a 10Khz triangle wave.
I follow the steps on this post
viewtopic.php?f=22&t=88259
But I can't get the frequency that I want.

[adafruit_support_mike]

Post the code you have now (between CODE tags please, the </> button) and we'll take a look.

[DanMx93]

This is the code:

Code: Select all

#include <Adafruit_MCP4725.h>
#include <Wire.h>

Adafruit_MCP4725 dac;

long freq = 10000;
long microSeconds = freq / 1000000;

const PROGMEM uint16_t up[8] = {
  0, 2, 4, 8, 16, 32, 64, 128
};

const PROGMEM uint16_t down[8] = {
  128, 64, 32, 16, 8, 4, 2, 0
};

int wavelenght = 8;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  dac.begin(0x62);

}

void loop() {
  // put your main code here, to run repeatedly:

  for(int i = 0; i < wavelenght; i++){
    dac.setVoltage(pgm_read_word(&(up[i])), false);
  }
  for(int i = 0; i < wavelenght; i++){
    dac.setVoltage(pgm_read_word(&(down[i])), false);
  }

  delayMicroseconds(microSeconds);
}

[adafruit_support_mike]

You have an inversion error.

The delay between samples is called the sampling period, and in general, period is a length of time divided by how often something happens. To find the period of a 10kHz signal in microseconds, you'd start with 1,000,000 microseconds per second, and divide that by the number of cycles per second (10,000). The result would be the number of microseconds per cycle: 100uS.

To get the sampling rate, you need to factor in the number of samples per cycle.. for your code, there are 16.. 8 going up and another 8 coming down. If a whole cycle of the 10kHz wave lasts 100uS and you have 16 samples per cycle, each gap needs to last 6.25uS.