mirror of
https://github.com/espressif/esp-idf.git
synced 2024-10-05 20:47:46 -04:00
82 lines
3.4 KiB
Markdown
82 lines
3.4 KiB
Markdown
|
| Supported Targets | ESP32 | ESP32-S3 |
|
||
|
|
| ----------------- | ----- | -------- |
|
||
|
|
|
||
|
|
# HC-SR04 Example
|
||
|
|
|
||
|
|
(See the README.md file in the upper level 'examples' directory for more information about examples.)
|
||
|
|
|
||
|
|
The capture module in MCPWM peripheral is designed to accurately log the time stamp on the hardware side when an event happens (compared to GPIO ISR which requires a software-based logging method). Each capture unit has three channels, which can be used together to capture IO events parallelly.
|
||
|
|
This example shows how to make use of the HW features to decode the pulse width signals generated from a common HC-SR04 sonar range finder -- [HC-SR04](https://www.sparkfun.com/products/15569).
|
||
|
|
|
||
|
|
The signal that HC-SR04 produces (and what can be handled by this example) is a simple pulse whose width indicates the measured distance. A pulse is required to send to HC-SR04 on `Trig` pin to begin a new measurement. Then the pulse described above will be sent back on `Echo` pin for decoding.
|
||
|
|
|
||
|
|
Typical signals:
|
||
|
|
|
||
|
|
```
|
||
|
|
Trig +-----+
|
||
|
|
| |
|
||
|
|
| |
|
||
|
|
-----+ +-----------------------
|
||
|
|
Echo +-----+
|
||
|
|
| |
|
||
|
|
| |
|
||
|
|
-----------------+ +-----------
|
||
|
|
|
||
|
|
+--------------------------------------->
|
||
|
|
Timeline
|
||
|
|
```
|
||
|
|
|
||
|
|
## How to Use Example
|
||
|
|
|
||
|
|
### Hardware Required
|
||
|
|
|
||
|
|
* An ESP development board
|
||
|
|
* HC-SR04 module
|
||
|
|
|
||
|
|
Connection :
|
||
|
|
|
||
|
|
```
|
||
|
|
+------+ +---------------------------------+
|
||
|
|
+-------+ | | |
|
||
|
|
| | VCC +--------------+ 5V |
|
||
|
|
+-------+ | | |
|
||
|
|
+ Echo +----=====>----+ GPIO18 (internal pull up) |
|
||
|
|
| | | |
|
||
|
|
+ Trig +----<=====----+ GPIO19 |
|
||
|
|
+-------| | | |
|
||
|
|
| | GND +--------------+ GND |
|
||
|
|
+-------| | | |
|
||
|
|
+------+ +---------------------------------+
|
||
|
|
```
|
||
|
|
|
||
|
|
### Build and Flash
|
||
|
|
|
||
|
|
Run `idf.py -p PORT flash monitor` to build, flash and monitor the project.
|
||
|
|
|
||
|
|
(To exit the serial monitor, type ``Ctrl-]``.)
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
## Example Output
|
||
|
|
|
||
|
|
```
|
||
|
|
I (314) hc-sr04: HC-SR04 example based on capture function from MCPWM
|
||
|
|
I (324) hc-sr04: Echo pin configured
|
||
|
|
I (324) gpio: GPIO[19]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
|
||
|
|
I (334) hc-sr04: Trig pin configured
|
||
|
|
I (344) hc-sr04: trig task started
|
||
|
|
I (444) hc-sr04: Pulse width: 419us, Measured distance: 7.22cm
|
||
|
|
I (544) hc-sr04: Pulse width: 419us, Measured distance: 7.22cm
|
||
|
|
I (644) hc-sr04: Pulse width: 416us, Measured distance: 7.17cm
|
||
|
|
I (744) hc-sr04: Pulse width: 415us, Measured distance: 7.16cm
|
||
|
|
I (844) hc-sr04: Pulse width: 415us, Measured distance: 7.16cm
|
||
|
|
I (944) hc-sr04: Pulse width: 416us, Measured distance: 7.17cm
|
||
|
|
I (1044) hc-sr04: Pulse width: 391us, Measured distance: 6.74cm
|
||
|
|
```
|
||
|
|
|
||
|
|
This example runs at 10Hz sampling rate. out of range data is dropped and only valid measurement is printed.
|
||
|
|
|
||
|
|
## Troubleshooting
|
||
|
|
|
||
|
|
For any technical queries, please open an [issue] (https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.
|