Cleanup 3rd party samples; update README.md; add some missing copyright, fix builds for boards without certain pin definitions

i2c/bmp280_i2c/bmp280_i2c.c

@@ -209,14 +209,14 @@ void bmp280_get_calib_params(struct bmp280_calib_param* params) {
 int main() {
     stdio_init_all();
 
-    // useful information for picotool
-    bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
-    bi_decl(bi_program_description("BMP280 I2C example for the Raspberry Pi Pico"));
-
 #if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN)
     #warning i2c / bmp280_i2c example requires a board with I2C pins
         puts("Default I2C pins were not defined");
 #else
+    // useful information for picotool
+    bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
+    bi_decl(bi_program_description("BMP280 I2C example for the Raspberry Pi Pico"));
+
     printf("Hello, BMP280! Reading temperaure and pressure values from sensor...\n");
 
     // I2C is "open drain", pull ups to keep signal high when no data is being sent

i2c/mcp9808_i2c/mcp9808_i2c.c

@@ -66,7 +66,7 @@ float mcp9808_convert_temp(uint8_t upper_byte, uint8_t lower_byte) {
     return temperature;
 }
 
-
+#ifdef i2c_default
 void mcp9808_set_limits() {
 
     //Set an upper limit of 30°C for the temperature
@@ -97,7 +97,7 @@ void mcp9808_set_limits() {
     buf[2] = crit_temp_lsb;;
     i2c_write_blocking(i2c_default, ADDRESS, buf, 3, false);
 }
-
+#endif
 
 int main() {
 
@@ -117,7 +117,6 @@ int main() {
     gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN);
     // Make the I2C pins available to picotool
     bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
-#endif
 
     mcp9808_set_limits();
 
@@ -144,4 +143,5 @@ int main() {
 
         sleep_ms(1000);
     }
+#endif
 }

i2c/mma8451_i2c/mma8451_i2c.c

@@ -56,11 +56,13 @@ float mma8451_convert_accel(uint16_t raw_accel) {
     return acceleration;
 }
 
+#ifdef i2c_default
 void mma8451_set_state(uint8_t state) {
     buf[0] = REG_CTRL_REG1;
     buf[1] = state; // Set RST bit to 1
     i2c_write_blocking(i2c_default, ADDRESS, buf, 2, false);
 }
+#endif
 
 int main() {
     stdio_init_all();

i2c/oled_i2c/oled_i2c.c

@@ -231,14 +231,14 @@ void render(uint8_t *buf, struct render_area *area) {
 int main() {
     stdio_init_all();
 
-    // useful information for picotool
-    bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
-    bi_decl(bi_program_description("OLED I2C example for the Raspberry Pi Pico"));
-
 #if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN)
 #warning i2c / oled_i2d example requires a board with I2C pins
     puts("Default I2C pins were not defined");
 #else
+    // useful information for picotool
+    bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
+    bi_decl(bi_program_description("OLED I2C example for the Raspberry Pi Pico"));
+
     printf("Hello, OLED display! Look at my raspberries..\n");
 
     // I2C is "open drain", pull ups to keep signal high when no data is being

i2c/pcf8523_i2c/pcf8523_i2c.c

@@ -20,11 +20,11 @@
    GND (physical pin 38)  -> GND on PCF8520 board
 */
 
+#ifdef i2c_default
+
 // By default these devices  are on bus address 0x68
 static int addr = 0x68;
 
-#ifdef i2c_default
-
 static void pcf8520_reset() {
     // Two byte reset. First byte register, second byte data
     // There are a load more options to set up the device in different ways that could be added here
@@ -90,8 +90,6 @@ void pcf8520_set_alarm() {
     }
 }
 
-#endif
-
 void pcf8520_check_alarm() {
     // Check bit 3 of control register 2 for alarm flags
     uint8_t status[1];
@@ -106,6 +104,7 @@ void pcf8520_check_alarm() {
     }
 }
 
+
 void pcf8520_convert_time(int conv_time[7], const uint8_t raw_time[7]) {
     // Convert raw data into time
     conv_time[0] = (10 * (int) ((raw_time[0] & 0x70) >> 4)) + ((int) (raw_time[0] & 0x0F));
@@ -116,6 +115,7 @@ void pcf8520_convert_time(int conv_time[7], const uint8_t raw_time[7]) {
     conv_time[5] = (10 * (int) ((raw_time[5] & 0x10) >> 4)) + ((int) (raw_time[5] & 0x0F));
     conv_time[6] = (10 * (int) ((raw_time[6] & 0xF0) >> 4)) + ((int) (raw_time[6] & 0x0F));
 }
+#endif
 
 int main() {
     stdio_init_all();
@@ -158,7 +158,7 @@ int main() {
         // Clear terminal 
         printf("\e[1;1H\e[2J");
     }
+#endif
     return 0;
 }
 
-#endif