- I tried this code and it worked in arduino IDE for ESP32. Note: I used it to generate 200kHz and had steps in the output wave. Do change as per your need.
https://github.com/krzychb/dac-cosine
I build a signal generator to produce sinus signals from 18Hz to 250kHz.
From 50Hz to 100kHz the difference to the wished frequency is about 1%
And it works without CPU after initialisation.
- // Function generator Sin
- // (C) Helmut Weber
- //
- // Provided as is as example
- // Free for everyone
- //
- // 50 Hz - 200000Hz: frequency error ~ 1%
- // from 17 Hz - 250000 possible
- // based on:
- // https://github.com/krzychb/dac-cosine
- // clk_8m_div and frequency_step are computed to give the best result for the wished frequency
- /* DAC Cosine Generator Example
- This example code is in the Public Domain (or CC0 licensed, at your option.)
- Unless required by applicable law or agreed to in writing, this
- software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
- CONDITIONS OF ANY KIND, either express or implied.
- */
- #include <stdio.h>
- #include <string.h>
- #include <stdlib.h>
- #include "freertos/FreeRTOS.h"
- #include "freertos/task.h"
- #include "freertos/queue.h"
- #include "soc/rtc_io_reg.h"
- #include "soc/rtc_cntl_reg.h"
- #include "soc/sens_reg.h"
- #include "soc/rtc.h"
- #include "driver/dac.h"
- /* Declare global sine waveform parameters
- * so they may be then accessed and changed from debugger
- * over an JTAG interface
- */
- // Esp32 @ 240 MHz:
- // f=125.6*step/(div+1) [div=0..7] [calc: (div+1)]
- // step0:
- // 0=15.61Hz 1=--
- // step 1:
- // 0 = 125.6 Hz 1 = 62.50 Hz 2 = 41.67Hz 3=31.35Hz 4=25.00Hz 5=20.92Hz 6=17.86Hz 7=15.63Hz
- // step 2:125,6
- // 0= 250.0 Hz 1=125Hz 2=83.68 Hz 3=62.5 Hz 4=50.1 Hz 5=41.74Hz 6=35.74 Hz 7=31.35Hz
- // step 10
- // 0 = 1.248 kHz 1 = 625.4 Hz 2 = 417.4 Hz (noisy) 3 = 31.33 Hz 4 = 250.6 5 = 208.3 Hz 6=178.9 7=156.3
- // step 100:
- // 0: 12.53 kHz 1 = 6.266 kHz 2=4.173kHz 3= 3.127 kHz 4=2.505 kHz 6=1.789 kHz 7=1.565KHz
- // step 500:
- // 0: 62.54 kHz (noisy) 1 = 31.33 kHz 2 = 20.86 kHz 5 = 10.5 kHz 6 =20.88 KhZ 7=
- // step 1000:
- // 0 = 125 kHz, 1 = 62.11 kHz, 5 = 20.73 kHz ==>>> 10 = 42.02 kHz 100
- // step 2000
- // 0: 249.4 kHz(unten verzerrt) 1 = 125.8 kHz (noisy) 5 = 41.5 kHz (noisy)
- int clk_8m_div = 1; // RTC 8M clock divider (division is by clk_8m_div+1, i.e. 0 means 8MHz frequency)
- int frequency_step = 7; // Frequency step for CW generator
- int scale = 1; // 50% of the full scale // scale 0 == fill scale = bad signal (no longer a sine wave)
- int offset; // leave it default / 0 = no any offset
- int invert = 2; // invert MSB to get sine waveform // 3: invert 180°
- /*
- * Enable cosine waveform generator on a DAC channel
- */
- void dac_cosine_enable(dac_channel_t channel)
- {
- // Enable tone generator common to both channels
- SET_PERI_REG_MASK(SENS_SAR_DAC_CTRL1_REG, SENS_SW_TONE_EN);
- switch(channel) {
- case DAC_CHANNEL_1:
- // Enable / connect tone tone generator on / to this channel
- SET_PERI_REG_MASK(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_CW_EN1_M);
- // Invert MSB, otherwise part of waveform will have inverted
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_INV1, 2, SENS_DAC_INV1_S);
- break;
- case DAC_CHANNEL_2:
- SET_PERI_REG_MASK(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_CW_EN2_M);
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_INV2, 2, SENS_DAC_INV2_S);
- break;
- default :
- printf("Channel %d\n", channel);
- }
- }
- /*
- * Set frequency of internal CW generator common to both DAC channels
- *
- * clk_8m_div: 0b000 - 0b111
- * frequency_step: range 0x0001 - 0xFFFF
- *
- */
- void dac_frequency_set(int clk_8m_div, int frequency_step)
- {
- REG_SET_FIELD(RTC_CNTL_CLK_CONF_REG, RTC_CNTL_CK8M_DIV_SEL, clk_8m_div);
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL1_REG, SENS_SW_FSTEP, frequency_step, SENS_SW_FSTEP_S);
- }
- /*
- * Scale output of a DAC channel using two bit pattern:
- *
- * - 00: no scale
- * - 01: scale to 1/2
- * - 10: scale to 1/4
- * - 11: scale to 1/8
- *
- */
- void dac_scale_set(dac_channel_t channel, int scale)
- {
- switch(channel) {
- case DAC_CHANNEL_1:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_SCALE1, scale, SENS_DAC_SCALE1_S);
- break;
- case DAC_CHANNEL_2:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_SCALE2, scale, SENS_DAC_SCALE2_S);
- break;
- default :
- printf("Channel %d\n", channel);
- }
- }
- /*
- * Offset output of a DAC channel
- *
- * Range 0x00 - 0xFF
- *
- */
- void dac_offset_set(dac_channel_t channel, int offset)
- {
- switch(channel) {
- case DAC_CHANNEL_1:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_DC1, offset, SENS_DAC_DC1_S);
- break;
- case DAC_CHANNEL_2:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_DC2, offset, SENS_DAC_DC2_S);
- break;
- default :
- printf("Channel %d\n", channel);
- }
- }
- /*
- * Invert output pattern of a DAC channel
- *
- * - 00: does not invert any bits,
- * - 01: inverts all bits,
- * - 10: inverts MSB,
- * - 11: inverts all bits except for MSB
- *
- */
- void dac_invert_set(dac_channel_t channel, int invert)
- {
- switch(channel) {
- case DAC_CHANNEL_1:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_INV1, invert, SENS_DAC_INV1_S);
- break;
- case DAC_CHANNEL_2:
- SET_PERI_REG_BITS(SENS_SAR_DAC_CTRL2_REG, SENS_DAC_INV2, invert, SENS_DAC_INV2_S);
- break;
- default :
- printf("Channel %d\n", channel);
- }
- }
- /*
- * Main task that let you test CW parameters in action
- *
- */
- void dactask(void* arg)
- {
- double f, f_target, delta, delta_min=9999999.0;
- int step_target=0, divi_target=0;
- //From experiments: f=125.6*step/(div+1)
- // this frequency is wanted:
- f_target=127000.0; // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
- // check all combinations of step iand divi to get the best guess:
- for (int step=1;step<2000; step++) {
- for (int divi=0; divi<8; divi++) {
- f=125.6*(double)step/(double)(divi+1);
- delta= abs((f_target-f));
- if (delta < delta_min) {delta_min=delta; step_target=step; divi_target=divi; }
- }
- }
- clk_8m_div=divi_target;
- frequency_step=step_target;
- printf("divi=%d step=%d\n",divi_target, step_target);
- while(1){
- // frequency setting is common to both channels
- dac_frequency_set(clk_8m_div, frequency_step);
- /* Tune parameters of channel 2 only
- * to see and compare changes against channel 1
- */
- dac_scale_set(DAC_CHANNEL_2, scale);
- dac_offset_set(DAC_CHANNEL_2, offset);
- dac_invert_set(DAC_CHANNEL_2, invert);
- float frequency = RTC_FAST_CLK_FREQ_APPROX / (1 + clk_8m_div) * (float) frequency_step / 65536;
- printf("THEORIE: clk_8m_div: %d, frequency step: %d, frequency: %.0f Hz\n", clk_8m_div, frequency_step, frequency);
- printf("PRACTICAL: frequency: %.0f Hz\n", 125.6*(float)frequency_step /(1 + (float)clk_8m_div) );
- printf("DAC2 scale: %d, offset %d, invert: %d\n", scale, offset, invert);
- vTaskDelay(2000/portTICK_PERIOD_MS);
- }
- }
- /*
- * Generate a sine waveform on both DAC channels:
- *
- * DAC_CHANNEL_1 - GPIO25
- * DAC_CHANNEL_2 - GPIO26
- *
- * Connect scope to both GPIO25 and GPIO26
- * to observe the waveform changes
- * in response to the parameter change
- */
- void app_main()
- {
- dac_cosine_enable(DAC_CHANNEL_1);
- dac_cosine_enable(DAC_CHANNEL_2);
- dac_output_enable(DAC_CHANNEL_1);
- dac_output_enable(DAC_CHANNEL_2);
- xTaskCreate(dactask, "dactask", 1024*3, NULL, 10, NULL);
- }