115 lines
No EOL
4.2 KiB
Markdown
115 lines
No EOL
4.2 KiB
Markdown
| Supported Targets | ESP32 |
|
|
| ----------------- | ----- |
|
|
|
|
# Wave generator Example
|
|
|
|
(See the README.md file in the upper level 'examples' directory for more information about examples.)
|
|
|
|
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.
|
|
|
|
Users can connect DAC output channel to their devices and use it as an simple analog signal output source.
|
|
|
|
## How to use this example
|
|
|
|
### Hardware Required
|
|
|
|
* A development board with ESP32 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
|
|
* A USB cable for power supply and programming
|
|
* A bunch of cables
|
|
* Target device
|
|
|
|
Make sure DAC output pin which is GPIO25 if channel 1 set, GPIO26 if channel 2 set, be connected to target device correctly.
|
|
|
|
### Configure the project
|
|
Under example folder, right click and select 'open terminal here'
|
|
|
|
Execute following statements in terminal:
|
|
|
|
```
|
|
idf.py menuconfig
|
|
```
|
|
|
|
In `Example Configuration`, set the following options:
|
|
|
|
#### DAC channel Num
|
|
|
|
ESP32 DAC contains two channels:
|
|
* **DAC_CHANNEL_1 (GPIO25), selected by default.**
|
|
* DAC_CHANNEL_2 (GPIO26)
|
|
|
|
#### Wave form
|
|
|
|
This example demonstrates one of the following waveforms:
|
|
* **Sine, selected by default.**
|
|
* Triangle
|
|
* Sawtooth
|
|
* Square
|
|
|
|
#### Wave frequency
|
|
|
|
About this option:
|
|
|
|
This signal generator has a range of frequency is 1kHz to 17kHz. **3kHz selected by default.**
|
|
|
|
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.
|
|
|
|
Based on the given frequency, the number of DAC output points for each cycle can be caluculated by following formula:
|
|
```num_of_output_points = 1000000(us)/(7 us * frequency)```
|
|
|
|
For example, with high frequency, 20kHz will results in generating only 10 output points, the curve will be sharp and zigzag.
|
|
|
|
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.
|
|
|
|
In short, there will be less output points per cycle in higher frequency, and more points in lower frequency.
|
|
|
|
After got the raw value, the real output voltage can be calculated through following formula (VDD is 3.3V):
|
|
|
|
```points_voltage = (VDD * DAC_OUTPUT / 255)```
|
|
|
|
The voltage is in range of 0~3300mV.
|
|
|
|
#### Enable output voltage log
|
|
|
|
**Disabled selected by default.**
|
|
|
|
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.
|
|
|
|
### Build and Flash
|
|
After configure step is done, build project and flash it to the board:
|
|
|
|
```
|
|
$ idf.py -p PORT flash monitor
|
|
```
|
|
|
|
(To exit the serial monitor, type ``Ctrl-]``.)
|
|
|
|
See the `Getting Started Guide` for full steps to configure and use ESP-IDF to build projects.
|
|
|
|
## Example Output
|
|
If oscilloscope is available, the target wave will show on oscilloscope after running this example.
|
|
|
|
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.
|
|
|
|
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:
|
|
|
|
```
|
|
I (318) Wave generator: DAC output channel: 1
|
|
I (318) Wave generator: GPIO:25
|
|
I (328) Wave generator: Waveform: Sine
|
|
I (328) Wave generator: Frequency(Hz): 3000
|
|
I (338) Wave generator: Output points num: 47
|
|
|
|
I (438) Wave generator: Output voltage(mV): 1656
|
|
I (538) Wave generator: Output voltage(mV): 1863
|
|
I (638) Wave generator: Output voltage(mV): 2083
|
|
I (738) Wave generator: Output voltage(mV): 2290
|
|
I (838) Wave generator: Output voltage(mV): 2484
|
|
I (938) Wave generator: Output voltage(mV): 2678
|
|
I (1038) Wave generator: Output voltage(mV): 2834
|
|
I (1138) Wave generator: Output voltage(mV): 2976
|
|
I (1238) Wave generator: Output voltage(mV): 3092
|
|
I (1338) Wave generator: Output voltage(mV): 3183
|
|
....
|
|
|
|
```
|
|
`Output voltage` in log means real voltage, in mV, which is output through GPIO by device. |