spi_master_simple

## SPI Master Simple

This example shows how to configure SPI master by POSIX APIs, this decreases dependence on hardware and platform.

## How to Use Example

Before project configuration and build, be sure to set the correct chip target using `idf.py set-target <chip_name>`.
And this example should be used together with [SPI Slave Simple](../spi_slave_simple/).

### Hardware Required

* 2 development boards based on espressif SoC
* 2 USB cables for power supply and programming
* 5 DuPont lines connecting SPI pins and GND between 2 development boards

### Configure the Project

Open the project configuration menu (`idf.py menuconfig`).

In the `Example Configuration` menu:

* Select SPI port in the `Select SPI Device` option, please note that not all SoC supports `SPI3`
* Set the SPI pins number in the following options according to your development board:
    - `SPI CS Pin Number`
    - `SPI SCLK Pin Number`
    - `SPI MOSI Pin Number`
    - `SPI MISO Pin Number`
* Set transmission count in the `SPI Testing Count of Transmitting Data`

### Build and Flash

Run `idf.py -p PORT flash monitor` to build, flash and monitor the project.

(To exit the serial monitor, type ``Ctrl-]``.)

## Example Output

As you run the example, you will see the following log:

```
I (0) cpu_start: Starting scheduler on APP CPU.
I (345) ext_vfs: Extended VFS version: 0.3.0
Opening device /dev/spi/2 for writing OK, fd=3.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
Write text total 32 bytes into device OK.
```