Examples: Add I2C controller example to read acc WhoAmI reg.

Author: microbit-carlos

examples/i2c_controller.cpp

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2022 Micro:bit Educational Foundation and contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "mbed.h"
+
+// I2C address of the on-board accelerometer & Who Am I values for LSM303AGR
+#define ACC_I2C_ADDR    (0x19 << 1)
+#define ACC_WHOAMI_REG  (0x0F)
+#define ACC_WHOAMI_VAL  (0x33)
+
+// Set up I2C with the internal I2C bus pins
+I2C i2c(I2C_SDA0, I2C_SCL0);
+
+// Set up serial and printf
+UnbufferedSerial pc_serial(USBTX, USBRX, 115200);
+FileHandle *mbed::mbed_override_console(int fd) {
+    return &pc_serial;
+}
+
+// Simple function to read a single register from an I2C device
+uint8_t i2c_read_register(uint8_t target_address, uint8_t reg_address) {
+    uint8_t error = i2c.write(target_address, (char *)&reg_address, 1, true);
+    if (error) {
+        printf("Error performing an I2C write.");
+        return 0;
+    }
+    uint8_t data = 0;
+    error = i2c.read(target_address, (char *)&data, 1);
+    if (error) {
+        printf("Error performing an I2C read.");
+    }
+    return data;
+}
+
+
+int main(void) {
+    uint8_t acc_who_am_i_value = i2c_read_register(ACC_I2C_ADDR, ACC_WHOAMI_REG);
+
+    printf("I2C accelerometer Who Am I value: %d\n", acc_who_am_i_value);
+    printf((acc_who_am_i_value == ACC_WHOAMI_VAL) ? "Success!\n" : "Invalid value :(\n");
+
+    while (1);
+}