samples: drivers: i2c: add i2c target api sample

Add simple sample which demonstrates how to setup a custom i2c target.

Signed-off-by: Bram Vlerick <bram.vlerick@openpixelsystems.org>

samples/drivers/i2c/custom_target/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(i2c_custom_target)
+
+target_sources(app PRIVATE src/main.c)

samples/drivers/i2c/custom_target/README.rst

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+.. zephyr:code-sample:: i2c-custom-target
+   :name: I2C Custom Target
+   :relevant-api: i2c_interface
+
+   Setup a custom I2C target on the I2C interface.
+
+Overview
+********
+
+This sample demonstrates how to setup an I2C custom target on the I2C interface
+using the :ref:`i2c-target-api`.
+
+Requirements
+************
+
+This sample requires an I2C peripheral which is capable of acting as a target.
+
+This sample has been tested on :ref:`lpcxpresso55s69`.
+
+Building and Running
+********************
+
+The code for this sample can be found in :zephyr_file:`samples/drivers/i2c_target`.
+
+To build and flash the application:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/drivers/i2c_target
+   :board: lpcxpresso55s69/lpc55s69/cpu0
+   :goals: flash
+   :compact:

samples/drivers/i2c/custom_target/boards/lpcxpresso55s69_lpc55s69_cpu0.overlay

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+/*
+ * Copyright (c) 2024 Open Pixel Systems
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&flexcomm4 {
+	status = "okay";
+};

samples/drivers/i2c/custom_target/prj.conf

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+CONFIG_I2C=y
+CONFIG_I2C_TARGET=y

samples/drivers/i2c/custom_target/sample.yaml

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+sample:
+  name: I2C custom target sample
+tests:
+  sample.drivers.i2c.custom_target:
+    tags: i2c_target
+    platform_allow:
+      - lpcxpresso55s69/lpc55s69/cpu0
+    harness: TBD

samples/drivers/i2c/custom_target/src/main.c

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+/*
+ * Copyright (c) 2024 Open Pixel Systems
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/sys/printk.h>
+#include <zephyr/drivers/i2c.h>
+
+static const struct device *bus = DEVICE_DT_GET(DT_NODELABEL(flexcomm4));
+static char last_byte;
+
+/*
+ * @brief Callback which is called when a write request is received from the master.
+ * @param config Pointer to the target configuration.
+ */
+int sample_target_write_requested_cb(struct i2c_target_config *config)
+{
+	printk("sample target write requested\n");
+	return 0;
+}
+
+/*
+ * @brief Callback which is called when a write is received from the master.
+ * @param config Pointer to the target configuration.
+ * @param val The byte received from the master.
+ */
+int sample_target_write_received_cb(struct i2c_target_config *config, uint8_t val)
+{
+	printk("sample target write received: 0x%02x\n", val);
+	last_byte = val;
+	return 0;
+}
+
+/*
+ * @brief Callback which is called when a read request is received from the master.
+ * @param config Pointer to the target configuration.
+ * @param val Pointer to the byte to be sent to the master.
+ */
+int sample_target_read_requested_cb(struct i2c_target_config *config, uint8_t *val)
+{
+	printk("sample target read request: 0x%02x\n", *val);
+	*val = 0x42;
+	return 0;
+}
+
+/*
+ * @brief Callback which is called when a read is processed from the master.
+ * @param config Pointer to the target configuration.
+ * @param val Pointer to the next byte to be sent to the master.
+ */
+int sample_target_read_processed_cb(struct i2c_target_config *config, uint8_t *val)
+{
+	printk("sample target read processed: 0x%02x\n", *val);
+	*val = 0x43;
+	return 0;
+}
+
+/*
+ * @brief Callback which is called when the master sends a stop condition.
+ * @param config Pointer to the target configuration.
+ */
+int sample_target_stop_cb(struct i2c_target_config *config)
+{
+	printk("sample target stop callback\n");
+	return 0;
+}
+
+static struct i2c_target_callbacks sample_target_callbacks = {
+	.write_requested = sample_target_write_requested_cb,
+	.write_received = sample_target_write_received_cb,
+	.read_requested = sample_target_read_requested_cb,
+	.read_processed = sample_target_read_processed_cb,
+	.stop = sample_target_stop_cb,
+};
+
+int main(void)
+{
+	struct i2c_target_config target_cfg = {
+		.address = 0x60,
+		.callbacks = &sample_target_callbacks,
+	};
+
+	printk("i2c custom target sample\n");
+
+	if (i2c_target_register(bus, &target_cfg) < 0) {
+		printk("Failed to register target\n");
+		return -1;
+	}
+
+	k_msleep(5000);
+
+	if (i2c_target_unregister(bus, &target_cfg) < 0) {
+		printk("Failed to unregister target\n");
+		return -1;
+	}
+
+	return 0;
+}