sam0_common: add uart modecfg

cpu/sam0_common/Makefile.features

@@ -3,5 +3,6 @@ FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_flashpage_raw
 FEATURES_PROVIDED += periph_flashpage_rwee
 FEATURES_PROVIDED += periph_gpio periph_gpio_irq
+FEATURES_PROVIDED += periph_uart_modecfg
 
 -include $(RIOTCPU)/cortexm_common/Makefile.features

cpu/sam0_common/include/periph_cpu_common.h

@@ -178,6 +178,22 @@ typedef enum {
     UART_FLAG_WAKEUP          = 0x2,    /**< wake from sleep on receive */
 } uart_flag_t;
 
+/**
+ * @brief   Available SERCOM UART data size selections
+ *
+ * 9 bit UART mode is currently unavailable as it is not supported by the common
+ * RIOT UART peripheral API.
+ * @{
+ */
+#define HAVE_UART_DATA_BITS_T
+typedef enum {
+    UART_DATA_BITS_5 = 0x5,   /**< 5 data bits */
+    UART_DATA_BITS_6 = 0x6,   /**< 6 data bits */
+    UART_DATA_BITS_7 = 0x7,   /**< 7 data bits */
+    UART_DATA_BITS_8 = 0x0,   /**< 8 data bits */
+} uart_data_bits_t;
+/** @} */
+
 /**
  * @brief   UART device configuration
  */

cpu/sam0_common/periph/uart.c

@@ -140,6 +140,47 @@ void uart_poweroff(uart_t uart)
     sercom_clk_dis(dev(uart));
 }
 
+#ifdef MODULE_PERIPH_UART_MODECFG
+int uart_mode(uart_t uart, uart_data_bits_t data_bits, uart_parity_t parity,
+              uart_stop_bits_t stop_bits)
+{
+    if (uart >= UART_NUMOF) {
+        return UART_NODEV;
+    }
+
+    if (stop_bits != UART_STOP_BITS_1 && stop_bits != UART_STOP_BITS_2) {
+        return UART_NOMODE;
+    }
+
+    if (parity != UART_PARITY_NONE && parity != UART_PARITY_EVEN &&
+            parity != UART_PARITY_ODD) {
+        return UART_NOMODE;
+    }
+
+    /* Disable UART first to remove write protect */
+    dev(uart)->CTRLA.bit.ENABLE = 0;
+    while (dev(uart)->SYNCBUSY.bit.ENABLE) {}
+
+    dev(uart)->CTRLB.bit.CHSIZE = data_bits;
+
+    if (parity == UART_PARITY_NONE) {
+        dev(uart)->CTRLA.bit.FORM = 0x0;
+    }
+    else {
+        dev(uart)->CTRLA.bit.FORM = 0x1;
+        dev(uart)->CTRLB.bit.PMODE = (parity == UART_PARITY_ODD) ? 1 : 0;
+    }
+
+    dev(uart)->CTRLB.bit.SBMODE = (stop_bits == UART_STOP_BITS_1) ? 0 : 1;
+
+    /* Enable UART again */
+    dev(uart)->CTRLA.bit.ENABLE = 1;
+    while (dev(uart)->SYNCBUSY.bit.ENABLE) {}
+
+    return UART_OK;
+}
+#endif
+
 static inline void irq_handler(unsigned uartnum)
 {
     if (dev(uartnum)->INTFLAG.bit.RXC) {