fix(xiao): keep SPI3 MOSI in board pin namespace

Author: cumin777

libraries/SPI/src/utility/spi_com.c

@@ -578,6 +578,9 @@ spi_status_e spi_transfer(spi_t *obj, const uint8_t *tx_buffer, uint8_t *rx_buff
 #if defined(USE_HALV2_DRIVER)
   uint32_t start_us;
 #endif
+  if (obj == NULL || obj->spi == NP) {
+    return SPI_ERROR;
+  }
   SPI_TypeDef *_SPI = obj->spi;
   uint8_t *tx_buf = (uint8_t *)tx_buffer;
 

variants/STM32C5xx/C593C(E-G)(T-U)_C5A3CG(T-U)/variant_XIAO_STM32C5.h

@@ -42,7 +42,7 @@
 #define PIN_SPI_SS1             NUM_DIGITAL_PINS
 #define PIN_SPI_SS2             NUM_DIGITAL_PINS
 #define PIN_SPI_SS3             NUM_DIGITAL_PINS
-#define PIN_SPI_MOSI            PB_15_ALT2
+#define PIN_SPI_MOSI            (PB15 | ALT2)
 #define PIN_SPI_MISO            PB0
 #define PIN_SPI_SCK             PE2