Fix issue if a pin has no peripheral

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/spi_com.c

@@ -198,6 +198,7 @@ void spi_init(spi_t *obj, uint32_t speed, spi_mode_e mode, uint8_t msb)
 
   /* Pins MOSI/MISO/SCLK must not be NP. ssel can be NP. */
   if(spi_mosi == NP || spi_miso == NP || spi_sclk == NP) {
+    printf("ERROR: at least one SPI pin has no peripheral\n");
     return;
   }
 

cores/arduino/stm32/twi.c

@@ -154,6 +154,12 @@ void i2c_custom_init(i2c_t *obj, i2c_timing_e timing, uint32_t addressingMode, u
   I2C_TypeDef *i2c_sda = pinmap_peripheral(obj->sda, PinMap_I2C_SDA);
   I2C_TypeDef *i2c_scl = pinmap_peripheral(obj->scl, PinMap_I2C_SCL);
 
+  //Pins SDA/SCL must not be NP
+  if(i2c_sda == NP || i2c_scl == NP) {
+    printf("ERROR: at least one I2C pin has no peripheral\n");
+    return;
+  }
+
   obj->i2c = pinmap_merge_peripheral(i2c_sda, i2c_scl);
 
   if(obj->i2c == NP) {

cores/arduino/stm32/uart.c

@@ -132,6 +132,12 @@ void uart_init(serial_t *obj)
   USART_TypeDef *uart_tx = pinmap_peripheral(obj->pin_tx, PinMap_UART_TX);
   USART_TypeDef *uart_rx = pinmap_peripheral(obj->pin_rx, PinMap_UART_RX);
 
+  //Pins Rx/Tx must not be NP
+  if(uart_rx == NP || uart_tx == NP) {
+    printf("ERROR: at least one UART pin has no peripheral\n");
+    return;
+  }
+
   // Get the peripheral name (UART_1, UART_2, ...) from the pin and assign it to the object
   obj->uart = pinmap_merge_peripheral(uart_tx, uart_rx);