kopia lustrzana https://github.com/espressif/esp-idf
113 wiersze
4.2 KiB
Markdown
113 wiersze
4.2 KiB
Markdown
| Supported Targets | ESP32 |
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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 a 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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* Target device or oscilloscope (not required)
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Make sure the DAC output pin (which is the GPIO25 if channel 1 set, GPIO26 if channel 2 set) is connected to the target device correctly.
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### Configure the project
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Open the project configuration menu (`idf.py menuconfig`).
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In the `Example Configuration` menu:
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* Use `DAC Channel Num` to select the DAC number.
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* Use `Waveform` to select the waveform type.
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* Select `Sine` (*default*), `Triangle`, `Sawtooth` or `Square` wave type.
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* Select `Wave frequency` from the available range.
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* Set the `Enable output voltage log` if you want to print the log in the terminal.
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#### Wave frequency
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For this example, the range of frequency is from 1 kHz to 17 kHz. **3 kHz is selected by default.**
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If you modify the frequency, you will change the number of DAC output points. This will affect the smoothness of the curve as well.
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Each output point value is calculated by the DAC resolution of 8-bits (0~255). All of these raw values 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 calculated through the following formula:
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```num_of_output_points = 1000000(us)/(7 us * frequency)```
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For example, with high frequency, 20 kHz will generate only 10 output points; the curve will be edgy.
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On the other hand, 500 Hz, a relative low frequency, will result in many DAC output points and the array will not be able to store all of the generated data.
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Thus, there will be less output points per cycle in higher frequency, and more points in lower frequency.
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After the raw value calculation, the real output voltage can be converted through the following formula (VDD is 3.3 V):
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```points_voltage = (VDD * DAC_OUTPUT / 255)```
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The voltage is within the range of 0~3300 mV.
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#### Enable output voltage log
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**Disabled selected by default.**
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If enabled, the expected voltage of each point will be printed on the terminal.
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### Build and Flash
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Build the project and flash it to the board, then run the monitor tool to view the serial output:
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Run `idf.py -p PORT flash monitor` to build, flash and monitor the project.
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for all the steps to configure and use the ESP-IDF to build projects.
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* [ESP-IDF Getting Started Guide on ESP32](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html)
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## Example Output
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If an oscilloscope is available, the target wave will be displayed in it after running this example.
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#### Sine:
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#### Triangle:
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#### Sawtooth:
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#### Square:
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The output log will be shown in the terminal as the following (if `Enable output voltage log` is enabled):
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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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## Troubleshooting
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For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.
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