Additional examples for specific h/w by our interns (#171)

adc/microphone_adc - Read analog values from a microphone and plot the measured sound amplitude.
i2c/bmp280_i2c - Read and convert temperature and pressure data from a BMP280 sensor, attached to an I2C bus.
i2c/lis3dh_i2c - Read acceleration and temperature value from a LIS3DH sensor via I2C
i2c/mcp9808_i2c - Read temperature, set limits and raise alerts when limits are surpassed.
i2c/mma8451_i2c - Read acceleration from a MMA8451 accelerometer and set range and precision for the data.
i2c/mpl3115a2_i2c - Interface with an MPL3115A2 altimeter, exploring interrupts and advanced board features, via I2C.
i2c/oled_i2c - Convert and display a bitmap on a 128x32 SSD1306-driven OLED display
i2c/pa1010d_i2c - Read GPS location data, parse and display data via I2C.
i2c/pcf8523_i2c - Read time and date values from a real time clock. Set current time and alarms on it.
uart/lcd_uart - Display text and symbols on a 16x02 RGB LCD display via UART

adc/microphone_adc/microphone_adc.c

@@ -0,0 +1,49 @@
+/**
+ * Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include "pico/stdlib.h"
+#include "hardware/gpio.h"
+#include "hardware/adc.h"
+#include "hardware/uart.h"
+#include "pico/binary_info.h"
+
+/* Example code to extract analog values from a microphone using the ADC
+   with accompanying Python file to plot these values
+
+   Connections on Raspberry Pi Pico board, other boards may vary.
+
+   GPIO 26/ADC0 (pin 31)-> AOUT or AUD on microphone board
+   3.3v (pin 36) -> VCC on microphone board
+   GND (pin 38)  -> GND on microphone board
+*/
+
+#define ADC_NUM 0
+#define ADC_PIN (26 + ADC_NUM)
+#define ADC_VREF 3.3
+#define ADC_RANGE (1 << 12)
+#define ADC_CONVERT (ADC_VREF / (ADC_RANGE - 1))
+
+int main() {
+    stdio_init_all();
+    printf("Beep boop, listening...\n");
+
+    bi_decl(bi_program_description("Analog microphone example for Raspberry Pi Pico")); // for picotool
+    bi_decl(bi_1pin_with_name(ADC_PIN, "ADC input pin"));
+
+    adc_init();
+    adc_gpio_init( ADC_PIN);
+    adc_select_input( ADC_NUM);
+
+    uint adc_raw;
+    while (1) {
+        adc_raw = adc_read(); // raw voltage from ADC
+        printf("%.2f\n", adc_raw * ADC_CONVERT);
+        sleep_ms(10);
+    }
+
+    return 0;
+}