samples: Add spi master sample

- Simple sample that sends bytes to SPI slave
- Tested on beagleconnect freedom

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

samples/spi_controller/CMakeLists.txt

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+cmake_path(SET ZephyrBase $ENV{ZEPHYR_BASE})
+set(DTC_OVERLAY_FILE ${ZephyrBase}/../modules/lib/Arduino-Zephyr-API/variants/${BOARD}/${BOARD}.overlay)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(spi_controller)
+
+target_sources(app PRIVATE src/app.cpp)
+
+zephyr_compile_options(-Wno-unused-variable -Wno-comment)

samples/spi_controller/README.rst

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+.. _spi_controller:
+
+SPI Controller
+###############
+
+Overview
+********
+
+A simple sample that sends incrementing byte to SPI peripheral.

samples/spi_controller/prj.conf

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+CONFIG_CPLUSPLUS=y
+CONFIG_ARDUINO_API=y
+CONFIG_SPI=y
+CONFIG_LOG=y
+CONFIG_LOG_OUTPUT=y
+CONFIG_LOG_MODE_IMMEDIATE=y

samples/spi_controller/src/app.cpp

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+/*
+ * Copyright (c) 2024 Ayush Singh <ayush@beagleboard.org>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "SPI.h"
+#include <Arduino.h>
+
+#define CHIPSELECT 3
+
+static uint8_t data = 0;
+
+void setup() {
+  SPI.begin();
+  pinMode(CHIPSELECT, OUTPUT);
+  digitalWrite(CHIPSELECT, HIGH);
+}
+
+void loop() {
+  SPI.beginTransaction(SPISettings(2000000, MSBFIRST, SPI_MODE0));
+  digitalWrite(CHIPSELECT, LOW);
+  SPI.transfer(data++);
+  digitalWrite(CHIPSELECT, HIGH);
+  SPI.endTransaction();
+  delay(1000);
+}