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README.md
Example: C++ SPI sensor read for MCU9250 inertial/giroscope sensor
(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example demonstrates usage of C++ SPI classes in ESP-IDF to read the WHO_AM_I register of the sensor.
In this example, the sdkconfig.defaults file sets the CONFIG_COMPILER_CXX_EXCEPTIONS option.
This enables both compile time support (-fexceptions compiler flag) and run-time support for C++ exception handling.
This is necessary for the C++ SPI API.
How to use example
Hardware Required
An MCU9250 sensor and any commonly available ESP32 development board.
Configure the project
idf.py menuconfig
Build and Flash
idf.py -p PORT flash monitor
(Replace PORT with the name of the serial port.)
(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 the sensor is read correctly:
...
I (0) cpu_start: Starting scheduler on APP CPU.
Result of WHO_AM_I register: 0x71
I (437) gpio: GPIO[23]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (447) gpio: GPIO[25]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (457) gpio: GPIO[26]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (467) gpio: GPIO[27]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
Done
If there's an error with the SPI peripheral:
...
I (0) cpu_start: Starting scheduler on APP CPU.
E (434) spi: spicommon_bus_initialize_io(429): mosi not valid
Couldn't read SPI!
If the SPI pins are not connected properly, the resulting read may just return 0, this error can not be detected:
...
I (0) cpu_start: Starting scheduler on APP CPU.
Result of WHO_AM_I register: 0x00
I (437) gpio: GPIO[23]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (447) gpio: GPIO[25]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (457) gpio: GPIO[26]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (467) gpio: GPIO[27]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0