wave_gen example: analog signal generator
This wave generator example does following: - An analog signal generator. - Offering four kinds of waveform: sine, triangle, sawtooth, square. - Customer can select their expected waveform, frequency, etc. All of them can be configured in menuconfig.
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7
examples/peripherals/wave_gen/CMakeLists.txt
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7
examples/peripherals/wave_gen/CMakeLists.txt
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# The following lines of boilerplate have to be in your project's CMakeLists
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# in this exact order for cmake to work correctly
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cmake_minimum_required(VERSION 3.5)
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set(SUPPORTED_TARGETS esp32)
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include($ENV{IDF_PATH}/tools/cmake/project.cmake)
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project(wave_gen)
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9
examples/peripherals/wave_gen/Makefile
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examples/peripherals/wave_gen/Makefile
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#
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# This is a project Makefile. It is assumed the directory this Makefile resides in is a
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# project subdirectory.
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#
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PROJECT_NAME := wave_gen
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include $(IDF_PATH)/make/project.mk
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112
examples/peripherals/wave_gen/README.md
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112
examples/peripherals/wave_gen/README.md
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# Wave generator Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example demonstrates how to implement a software controlled signal generator by utilizing the DAC and Timer Group drivers. All waveforms demonstrated in this example are generated by software.
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Users can connect DAC output channel to their devices and use it as an simple analog signal output source.
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## How to use this example
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### Hardware Required
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* A development board with ESP32 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
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* A USB cable for power supply and programming
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* A bunch of cables
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* Target device
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Make sure DAC output pin which is GPIO25 if channel 1 set, GPIO26 if channel 2 set, be connected to target device correctly.
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### Configure the project
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Under example folder, right click and select 'open terminal here'
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Execute following statements in terminal:
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```
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idf.py menuconfig
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```
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In `Example Configuration`, set the following options:
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#### DAC channel Num
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ESP32 DAC contains two channels:
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* **DAC_CHANNEL_1 (GPIO25), selected by default.**
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* DAC_CHANNEL_2 (GPIO26)
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#### Wave form
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This example demonstrates one of the following waveforms:
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* **Sine, selected by default.**
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* Triangle
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* Sawtooth
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* Square
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#### Wave frequency
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About this option:
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This signal generator has a range of frequency is 1kHz to 17kHz. **3kHz selected by default.**
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Modify the frequency will change the number of DAC output points. That will affect the smoothness of curve as well. Those output points are used to calculate the raw value(0~255) of each output point. All of these raw value are stored in an array.
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Based on the given frequency, the number of DAC output points for each cycle can be caluculated by following formula:
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```num_of_output_points = 1000000(us)/(7 us * frequency)```
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For example, with high frequency, 20kHz will results in generating only 10 output points, the curve will be sharp and zigzag.
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On the contrary, 500 Hz, low frequency relatively, will results in many DAC output points and the array cannot stores so many values that it will causes array overboundary.
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In short, there will be less output points per cycle in higher frequency, and more points in lower frequency.
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After got the raw value, the real output voltage can be calculated through following formula (VDD is 3.3V):
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```points_voltage = (VDD * DAC_OUTPUT / 255)```
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The voltage is in range of 0~3300mV.
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#### Enable output voltage log
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**Disabled selected by default.**
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If enabled, expected voltage of each points will be shown in terminal. It's intuitive for debugging and testing. If output example is needed, read **Example Output** chapter below.
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### Build and Flash
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After configure step is done, build project and flash it to the board:
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```
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$ idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the `Getting Started Guide` for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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If oscilloscope is available, the target wave will show on oscilloscope after running this example.
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Additionally, if more specific output voltage information is needed, run menuconfig and set "Enable print output voltage" to "Enabled". Then, more information will show as log in terminal.
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For example, set wave frequency, waveform to 3kHz and sine respectively, and also enable print output voltage option. The output information will show in log in terminal as following:
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```
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I (318) Wave generator: DAC output channel: 1
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I (318) Wave generator: GPIO:25
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I (328) Wave generator: Waveform: Sine
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I (328) Wave generator: Frequency(Hz): 3000
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I (338) Wave generator: Output points num: 47
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I (438) Wave generator: Output voltage(mV): 1656
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I (538) Wave generator: Output voltage(mV): 1863
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I (638) Wave generator: Output voltage(mV): 2083
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I (738) Wave generator: Output voltage(mV): 2290
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I (838) Wave generator: Output voltage(mV): 2484
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I (938) Wave generator: Output voltage(mV): 2678
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I (1038) Wave generator: Output voltage(mV): 2834
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I (1138) Wave generator: Output voltage(mV): 2976
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I (1238) Wave generator: Output voltage(mV): 3092
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I (1338) Wave generator: Output voltage(mV): 3183
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....
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```
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`Output voltage` in log means real voltage, in mV, which is output through GPIO by device.
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2
examples/peripherals/wave_gen/main/CMakeLists.txt
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examples/peripherals/wave_gen/main/CMakeLists.txt
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idf_component_register(SRCS "wave_gen_example_main.c"
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INCLUDE_DIRS ".")
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103
examples/peripherals/wave_gen/main/Kconfig.projbuild
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examples/peripherals/wave_gen/main/Kconfig.projbuild
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menu "Example Configuration"
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choice EXAMPLE_DAC_CHANNEL
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bool "DAC Channel Num"
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default EXAMPLE_DAC_CHANNEL_1
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help
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Select DAC channel used by the wave generator.
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config EXAMPLE_DAC_CHANNEL_1
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bool "DAC Channel 1 (GPIO25)"
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config EXAMPLE_DAC_CHANNEL_2
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bool "DAC Channel 2 (GPIO26)"
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endchoice
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config EXAMPLE_DAC_CHANNEL
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int
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default 0 if EXAMPLE_DAC_CHANNEL_1
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default 1 if EXAMPLE_DAC_CHANNEL_2
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choice EXAMPLE_WAVEFORM
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bool "Waveform"
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default EXAMPLE_WAVEFORM_SINE
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help
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Select waveform
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config EXAMPLE_WAVEFORM_SINE
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bool "Sine selected"
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config EXAMPLE_WAVEFORM_TRIANGLE
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bool "Triangle selected"
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config EXAMPLE_WAVEFORM_SAWTOOTH
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bool "Sawtooth selected"
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config EXAMPLE_WAVEFORM_SQUARE
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bool "Square selected"
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endchoice
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choice EXAMPLE_WAVE_FREQUENCY
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bool "Wave frequency"
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default EXAMPLE_WAVE_FREQ_3000
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help
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Select output wave frequency.
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config EXAMPLE_WAVE_FREQ_1000
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bool "1000 Hz"
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config EXAMPLE_WAVE_FREQ_2000
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bool "2000 Hz"
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config EXAMPLE_WAVE_FREQ_3000
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bool "3000 Hz"
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config EXAMPLE_WAVE_FREQ_4000
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bool "4000 Hz"
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config EXAMPLE_WAVE_FREQ_5000
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bool "5000 Hz"
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config EXAMPLE_WAVE_FREQ_6000
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bool "6000 Hz"
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config EXAMPLE_WAVE_FREQ_7000
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bool "7000 Hz"
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config EXAMPLE_WAVE_FREQ_8000
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bool "8000 Hz"
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config EXAMPLE_WAVE_FREQ_9000
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bool "9000 Hz"
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config EXAMPLE_WAVE_FREQ_10000
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bool "10000 Hz"
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config EXAMPLE_WAVE_FREQ_11000
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bool "11000 Hz"
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config EXAMPLE_WAVE_FREQ_12000
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bool "12000 Hz"
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config EXAMPLE_WAVE_FREQ_13000
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bool "13000 Hz"
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config EXAMPLE_WAVE_FREQ_14000
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bool "14000 Hz"
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config EXAMPLE_WAVE_FREQ_15000
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bool "15000 Hz"
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config EXAMPLE_WAVE_FREQ_16000
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bool "16000 Hz"
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config EXAMPLE_WAVE_FREQ_17000
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bool "17000 Hz"
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endchoice
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config EXAMPLE_WAVE_FREQUENCY
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int
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default 1000 if EXAMPLE_WAVE_FREQ_1000
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default 2000 if EXAMPLE_WAVE_FREQ_2000
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default 3000 if EXAMPLE_WAVE_FREQ_3000
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default 4000 if EXAMPLE_WAVE_FREQ_4000
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default 5000 if EXAMPLE_WAVE_FREQ_5000
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default 6000 if EXAMPLE_WAVE_FREQ_6000
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default 7000 if EXAMPLE_WAVE_FREQ_7000
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default 8000 if EXAMPLE_WAVE_FREQ_8000
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default 9000 if EXAMPLE_WAVE_FREQ_9000
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default 10000 if EXAMPLE_WAVE_FREQ_10000
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default 11000 if EXAMPLE_WAVE_FREQ_11000
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default 12000 if EXAMPLE_WAVE_FREQ_12000
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default 13000 if EXAMPLE_WAVE_FREQ_13000
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default 14000 if EXAMPLE_WAVE_FREQ_14000
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default 15000 if EXAMPLE_WAVE_FREQ_15000
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default 16000 if EXAMPLE_WAVE_FREQ_16000
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default 17000 if EXAMPLE_WAVE_FREQ_17000
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config EXAMPLE_LOG_VOLTAGE
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bool "Enable output voltage log"
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default n
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help
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If enabled, the output voltage(in mV) will show in log.
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endmenu
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3
examples/peripherals/wave_gen/main/component.mk
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3
examples/peripherals/wave_gen/main/component.mk
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#
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# Main Makefile. This is basically the same as a component makefile.
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#
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149
examples/peripherals/wave_gen/main/wave_gen_example_main.c
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149
examples/peripherals/wave_gen/main/wave_gen_example_main.c
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/* Wave Generator Example
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This example code is in the Public Domain (or CC0 licensed, at your option.)
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DAC output channel, waveform, wave frequency can be customized in menuconfig.
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If any questions about this example or more information is needed, please read README.md before your start.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <assert.h>
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "freertos/queue.h"
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#include "driver/gpio.h"
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#include "driver/dac.h"
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#include "driver/timer.h"
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#include "esp_log.h"
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/* The timer ISR has an execution time of 5.5 micro-seconds(us).
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Therefore, a timer period less than 5.5 us will cause trigger the interrupt watchdog.
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7 us is a safe interval that will not trigger the watchdog. No need to customize it.
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*/
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#define WITH_RELOAD 1
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#define TIMER_INTR_US 7 // Execution time of each ISR interval in micro-seconds
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#define TIMER_DIVIDER 16
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#define POINT_ARR_LEN 200 // Length of points array
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#define AMP_DAC 255 // Amplitude of DAC voltage. If it's more than 256 will causes dac_output_voltage() output 0.
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#define VDD 3300 // VDD is 3.3V, 3300mV
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#define CONST_PERIOD_2_PI 6.2832
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#define SEC_TO_MICRO_SEC(x) ((x) / 1000 / 1000) // Convert second to micro-second
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#define UNUSED_PARAM __attribute__((unused)) // A const period parameter which equals 2 * pai, used to calculate raw dac output value.
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#define TIMER_TICKS (TIMER_BASE_CLK / TIMER_DIVIDER) // TIMER_BASE_CLK = APB_CLK = 80MHz
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#define ALARM_VAL_US SEC_TO_MICRO_SEC(TIMER_INTR_US * TIMER_TICKS) // Alarm value in micro-seconds
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#define OUTPUT_POINT_NUM (int)(1000000 / (TIMER_INTR_US * FREQ) + 0.5) // The number of output wave points.
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#define DAC_CHAN CONFIG_EXAMPLE_DAC_CHANNEL // DAC_CHANNEL_1 (GPIO25) by default
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#define FREQ CONFIG_EXAMPLE_WAVE_FREQUENCY // 3kHz by default
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_Static_assert(OUTPUT_POINT_NUM <= POINT_ARR_LEN, "The CONFIG_EXAMPLE_WAVE_FREQUENCY is too low and using too long buffer.");
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static int raw_val[POINT_ARR_LEN]; // Used to store raw values
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static int volt_val[POINT_ARR_LEN]; // Used to store voltage values(in mV)
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static const char *TAG = "wave_gen";
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static int g_index = 0;
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/* Timer interrupt service routine */
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static void IRAM_ATTR timer0_ISR(void *ptr)
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{
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timer_group_clr_intr_status_in_isr(TIMER_GROUP_0, TIMER_0);
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timer_group_enable_alarm_in_isr(TIMER_GROUP_0, TIMER_0);
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int *head = (int*)ptr;
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/* DAC output ISR has an execution time of 4.4 us*/
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if (g_index >= OUTPUT_POINT_NUM) g_index = 0;
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dac_output_voltage(DAC_CHAN, *(head + g_index));
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g_index++;
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}
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/* Timer group0 TIMER_0 initialization */
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static void example_timer_init(int timer_idx, bool auto_reload)
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{
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esp_err_t ret;
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timer_config_t config = {
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.divider = TIMER_DIVIDER,
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.counter_dir = TIMER_COUNT_UP,
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.counter_en = TIMER_PAUSE,
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.alarm_en = TIMER_ALARM_EN,
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.intr_type = TIMER_INTR_LEVEL,
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.auto_reload = auto_reload,
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};
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ret = timer_init(TIMER_GROUP_0, timer_idx, &config);
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ESP_ERROR_CHECK(ret);
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ret = timer_set_counter_value(TIMER_GROUP_0, timer_idx, 0x00000000ULL);
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ESP_ERROR_CHECK(ret);
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ret = timer_set_alarm_value(TIMER_GROUP_0, timer_idx, ALARM_VAL_US);
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ESP_ERROR_CHECK(ret);
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ret = timer_enable_intr(TIMER_GROUP_0, TIMER_0);
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ESP_ERROR_CHECK(ret);
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/* Register an ISR handler */
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timer_isr_register(TIMER_GROUP_0, timer_idx, timer0_ISR, (void *)raw_val, ESP_INTR_FLAG_IRAM, NULL);
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}
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static void prepare_data(int pnt_num)
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{
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timer_pause(TIMER_GROUP_0, TIMER_0);
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for (int i = 0; i < pnt_num; i ++) {
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#ifdef CONFIG_EXAMPLE_WAVEFORM_SINE
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raw_val[i] = (int)((sin( i * CONST_PERIOD_2_PI / pnt_num) + 1) * (double)(AMP_DAC)/2 + 0.5);
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#elif CONFIG_EXAMPLE_WAVEFORM_TRIANGLE
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raw_val[i] = (i > (pnt_num/2)) ? (2 * AMP_DAC * (pnt_num - i) / pnt_num) : (2 * AMP_DAC * i / pnt_num);
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#elif CONFIG_EXAMPLE_WAVEFORM_SAWTOOTH
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raw_val[i] = (i == pnt_num) ? 0 : (i * AMP_DAC / pnt_num);
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#elif CONFIG_EXAMPLE_WAVEFORM_SQUARE
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raw_val[i] = (i < (pnt_num/2)) ? AMP_DAC : 0;
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#endif
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volt_val[i] = (int)(VDD * raw_val[i] / (float)AMP_DAC);
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}
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timer_start(TIMER_GROUP_0, TIMER_0);
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}
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static void log_info(void)
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{
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ESP_LOGI(TAG, "DAC output channel: %d", DAC_CHAN);
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if (DAC_CHAN == DAC_CHANNEL_1) {
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ESP_LOGI(TAG, "GPIO:%d", GPIO_NUM_25);
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} else {
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ESP_LOGI(TAG, "GPIO:%d", GPIO_NUM_26);
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}
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#ifdef CONFIG_EXAMPLE_WAVEFORM_SINE
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ESP_LOGI(TAG, "Waveform: SINE");
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#elif CONFIG_EXAMPLE_WAVEFORM_TRIANGLE
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ESP_LOGI(TAG, "Waveform: TRIANGLE");
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#elif CONFIG_EXAMPLE_WAVEFORM_SAWTOOTH
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ESP_LOGI(TAG, "Waveform: SAWTOOTH");
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#elif CONFIG_EXAMPLE_WAVEFORM_SQUARE
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ESP_LOGI(TAG, "Waveform: SQUARE");
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#endif
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ESP_LOGI(TAG, "Frequency(Hz): %d", FREQ);
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ESP_LOGI(TAG, "Output points num: %d\n", OUTPUT_POINT_NUM);
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}
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void app_main(void)
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{
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esp_err_t ret;
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example_timer_init(TIMER_0, WITH_RELOAD);
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ret = dac_output_enable(DAC_CHAN);
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ESP_ERROR_CHECK(ret);
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log_info();
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g_index = 0;
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prepare_data(OUTPUT_POINT_NUM);
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while(1) {
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vTaskDelay(10);
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#if CONFIG_EXAMPLE_LOG_VOLTAGE
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if (g_index < OUTPUT_POINT_NUM) {
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ESP_LOGI(TAG, "Output voltage(mV): %d", volt_val[g_index]);
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ESP_LOGD(TAG, "g_index: %d\n", g_index);
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}
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#endif
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}
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}
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