mirror of
https://github.com/espressif/esp-idf.git
synced 2024-10-05 20:47:46 -04:00
76 lines
2.5 KiB
Markdown
76 lines
2.5 KiB
Markdown
| Supported Targets | ESP32-S2 | ESP32-S3 |
|
|
| ----------------- | -------- | -------- |
|
|
|
|
# ULP-RISC-V bitbanged UART transmit:
|
|
|
|
This example demonstrates how to program the ULP-RISC-V coprocessor to bitbang an UART TX line. This can be used to log output directly from the ULP, even when the main CPU is in deep sleep.
|
|
|
|
|
|
## How to use example
|
|
|
|
### Hardware Required
|
|
|
|
The example can be run on any ESP32-S2 or ESP32-S3 based development board connected to a computer with a single USB cable for flashing and monitoring. The external interface should have 3.3V outputs. You may use e.g. 3.3V compatible USB-to-Serial dongle.
|
|
|
|
### Setup the Hardware
|
|
|
|
Connect the external serial interface to the board as follows.
|
|
|
|
```
|
|
-----------------------------------------------------------------------------------------
|
|
| Target chip Interface | Kconfig Option | Default ESP Pin | External UART Pin |
|
|
| ----------------------|--------------------|----------------------|--------------------
|
|
| Transmit Data (TxD) | EXAMPLE_UART_TXD | GPIO4 | RxD |
|
|
| Ground | n/a | GND | GND |
|
|
-----------------------------------------------------------------------------------------
|
|
```
|
|
Note: Some GPIOs can not be used with certain chips because they are reserved for internal use. Please refer to UART documentation for selected target.
|
|
|
|
### Configure the project
|
|
|
|
Use the command below to configure project using Kconfig menu as showed in the table above. The baudrate can be changed with by configuring `ULP_RISCV_UART_BAUDRATE` under `components` -> `ULP`, but it is recommended to keep the baudrate low, as driver will not be able to accurately output higher rates.
|
|
|
|
```
|
|
idf.py menuconfig
|
|
```
|
|
|
|
### Build and Flash
|
|
|
|
Build the project and flash it to the board, then run monitor tool to view serial output:
|
|
|
|
```
|
|
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
|
|
|
|
Output from main CPU:
|
|
|
|
```
|
|
Not a ULP wakeup, initializing it!
|
|
Entering in deep sleep
|
|
```
|
|
|
|
Output from ULP-RISCV:
|
|
|
|
``
|
|
Hello World from ULP-RISCV!
|
|
Cnt: 0x00000000
|
|
Hello World from ULP-RISCV!
|
|
Cnt: 0x00000001
|
|
Hello World from ULP-RISCV!
|
|
Cnt: 0x00000002
|
|
Hello World from ULP-RISCV!
|
|
Cnt: 0x00000003
|
|
Hello World from ULP-RISCV!
|
|
Cnt: 0x00000004
|
|
``
|
|
|
|
## Troubleshoot
|
|
|
|
If the received output contains garbled characters then try to lower the baudrate (ULP_RISCV_UART_BAUDRATE) using `menuconfig`.
|