92 lines
3.1 KiB
Markdown
92 lines
3.1 KiB
Markdown
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# Semihosting VFS driver 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 demonstrates how to use semihosting VFS driver with ESP32. Example does the following steps:
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1. Uses `esp_vfs_semihost_register` function to register exposed host directory in VFS, enabling C standard library and POSIX functions to be used.
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2. Redirects `stdout` from the UART to the file on the host using `freopen`.
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3. Prints several messages to the redirected.
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4. Switches back to UART `stdout` using `freopen`.
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5. Opens text file on the host.
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6. Reads the file and prints its content on stdout.
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## How to use example
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### Hardware and tools required
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This example does not require any special hardware, and can be run on any common development board.
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This example requires [OpenOCD](https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/jtag-debugging/index.html#run-openocd).
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NOTE: In order to run this example you need OpenOCD version `v0.10.0-esp32-20190313` or later.
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Run OpenOCD using command:
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```
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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
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```
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This command also configures OpenOCD to expose example project `data` subdirectory to the target's semihosting VFS driver.
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### Configure the project
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If using Make based build system, run `make menuconfig` and set serial port under Serial Flasher Options.
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If using CMake based build system, no configuration is required.
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### Build and flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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make -j4 flash monitor
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```
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Or, for CMake based build system (replace PORT with serial port name):
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```
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idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example output
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There are two types of outputs produced by example:
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1. File `esp32_stdout.txt` in the host directory mounted to the target:
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```
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W (274) example: Switched to semihosted stdout
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Semihosted stdout write 0
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Semihosted stdout write 1
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Semihosted stdout write 2
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...
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Semihosted stdout write 98
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Semihosted stdout write 99
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W (274) example: Switch to UART stdout
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```
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2. On the boards console:
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```
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W (274) example: Switch to semihosted stdout
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W (274) example: Switched back to UART stdout
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I (274) example: Wrote 2798 bytes
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====================== HOST DATA START =========================
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The following are the graphical (non-control) characters defined by
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ISO 8859-1 (1987). Descriptions in words aren't all that helpful,
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but they're the best we can do in text. A graphics file illustrating
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the character set should be available from the same archive as this
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file.
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Hex Description Hex Description
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20 SPACE
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...
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7D RIGHT CURLY BRACKET FD SMALL LETTER Y WITH ACUTE
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7E TILDE FE SMALL LETTER THORN (Icelandic)
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FF SMALL LETTER Y WITH DIAERESIS
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====================== HOST DATA END =========================
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I (694) example: Read 6121 bytes
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```
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