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README.md
Semihosting VFS driver example
(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example demonstrates how to use semihosting VFS driver with ESP32. Example does the following steps:
- Uses
esp_vfs_semihost_register
function to register exposed host directory in VFS, enabling C standard library and POSIX functions to be used. - Redirects
stdout
from the UART to the file on the host usingfreopen
. - Prints several messages to the redirected.
- Switches back to UART
stdout
usingfreopen
. - Opens text file on the host.
- Reads the file and prints its content on stdout.
How to use example
Hardware and tools required
This example does not require any special hardware, and can be run on any common development board.
This example requires OpenOCD.
NOTE: In order to run this example you need OpenOCD version v0.10.0-esp32-20190313
or later.
Run OpenOCD using command:
bin/openocd -s share/openocd/scripts -f interface/ftdi/esp32_devkitj_v1.cfg -c 'set ESP_SEMIHOST_BASEDIR '$IDF_PATH/examples/storage/semihost_vfs/data -f board/esp-wroom-32.cfg
This command also configures OpenOCD to expose example project data
subdirectory to the target's semihosting VFS driver.
Configure the project
If using Make based build system, run make menuconfig
and set serial port under Serial Flasher Options.
If using CMake based build system, no configuration is required.
Build and flash
Build the project and flash it to the board, then run monitor tool to view serial output:
make -j4 flash monitor
Or, for CMake based build system (replace PORT with serial port name):
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
There are two types of outputs produced by example:
- File
esp32_stdout.txt
in the host directory mounted to the target:
W (274) example: Switched to semihosted stdout
Semihosted stdout write 0
Semihosted stdout write 1
Semihosted stdout write 2
...
Semihosted stdout write 98
Semihosted stdout write 99
W (274) example: Switch to UART stdout
- On the boards console:
W (274) example: Switch to semihosted stdout
W (274) example: Switched back to UART stdout
I (274) example: Wrote 2798 bytes
====================== HOST DATA START =========================
The following are the graphical (non-control) characters defined by
ISO 8859-1 (1987). Descriptions in words aren't all that helpful,
but they're the best we can do in text. A graphics file illustrating
the character set should be available from the same archive as this
file.
Hex Description Hex Description
20 SPACE
...
7D RIGHT CURLY BRACKET FD SMALL LETTER Y WITH ACUTE
7E TILDE FE SMALL LETTER THORN (Icelandic)
FF SMALL LETTER Y WITH DIAERESIS
====================== HOST DATA END =========================
I (694) example: Read 6121 bytes