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Supported Targets	ESP32	ESP32-C3	ESP32-S2	ESP32-S3

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