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70 lines
3.2 KiB
Markdown
70 lines
3.2 KiB
Markdown
| Supported Targets | ESP32 | ESP32-C3 | ESP32-C6 | ESP32-S2 | ESP32-S3 |
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| ----------------- | ----- | -------- | -------- | -------- | -------- |
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# Sigma Delta Modulation DAC 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 uses the sigma-delta driver to generate modulated output on a GPIO. If you filter the output signal with an active or passive filter, you can get a 1 KHz sine wave.
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## How to use example
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### Hardware Required
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* A development board with any supported Espressif 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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* An active or passive low-pass filter. Connect them as below:
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```
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┌──────────────────────────────┐
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│ ESP │ ┌───────────────────┐
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│ │ │ Active or Passive │ Sine Wave
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│ EXAMPLE_SIGMA_DELTA_GPIO_NUM ├────►│ Low-pass Filter ├──────────────
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└──────────────────────────────┘ └───────────────────┘
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```
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### Configure the project
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The main configurations can be update by the macro that defined at the top of the [example source file](main/sdm_dac_example_main.c), including the output gpio, timer callback interval and the sine wave frequency and amplitude.
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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](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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Once the upload is complete and the board is reset, the program should start running. This is reported on the monitor as below:
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```
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...
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I (299) main_task: Calling app_main()
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I (309) gpio: GPIO[0]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
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I (309) sdm_dac: Sigma-delta output is attached to GPIO 0
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I (319) sdm_dac: Timer allocated with resolution 10000000 Hz
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I (329) sdm_dac: Timer callback registered, interval 10 us
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I (329) sdm_dac: Timer enabled
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I (339) sdm_dac: Output start
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```
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After the output stated, you can monitor the output signal by an oscilloscope.
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If you monitor on the GPIO directly, you can see the raw SDM output, it consists by square waves (i.e. pulse) with different density
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If you monitor the signal after a low-pass filter, you can see the pulses are filtered into a sine wave already
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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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If a lot of glitches appear in the filtered sine wave, it might be the inappropriate GND that the probe connected, please try to choose the GND that nearby the filter.
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