cpu: efm32: add support for non-standard UART modes.

cpu/efm32/Makefile.features

+include $(RIOTCPU)/efm32/efm32-features.mk
+
 FEATURES_PROVIDED += periph_cpuid
 FEATURES_PROVIDED += periph_flashpage
 
@@ -8,4 +10,8 @@ ifeq (1,$(EFM32_TNRG))
   FEATURES_PROVIDED += periph_hwrng
 endif
 
+ifeq (1,$(EFM32_UART_MODES))
+  export CFLAGS += -DEFM32_UART_MODES=1
+endif
+
 include $(RIOTCPU)/cortexm_common/Makefile.features

cpu/efm32/efm32-features.mk

+# This file provides defaults for additional EFM32-specific features. You
+# should override them from the command line, or in your Makefile. Note that
+# some features may not be applicable to all EFM32 boards or CPUs.
+export EFM32_UART_MODES ?= 0

cpu/efm32/include/periph_cpu.h

@@ -359,6 +359,20 @@ typedef struct {
 } timer_conf_t;
 /** @} */
 
+/**
+ * @brief   Internal macro for combining UART modes data bits (x), stop bits
+ *          (y, in half bits) and parity (z).
+ */
+#define UART_MODE(x, y, z)      ((z << 8) | ((y * 2) << 4) | x)
+
+/**
+ * @brief   Internal, pre-defined UART modes.
+ * @{
+ */
+#define UART_MODE_8N1           UART_MODE(8, 1, 0)
+#define UART_MODE_8E1           UART_MODE(8, 1, 2)
+/** @} */
+
 /**
  * @brief   UART device configuration.
  */
@@ -366,7 +380,10 @@ typedef struct {
     void *dev;              /**< UART, USART or LEUART device used */
     gpio_t rx_pin;          /**< pin used for RX */
     gpio_t tx_pin;          /**< pin used for TX */
-    uint32_t loc;           /**< location of USART pins */
+    uint32_t loc;           /**< location of UART pins */
+#if EFM32_UART_MODES
+    uint32_t mode;          /**< UART mode of operation */
+#endif
     CMU_Clock_TypeDef cmu;  /**< the device CMU channel */
     IRQn_Type irq;          /**< the devices base IRQ channel */
 } uart_conf_t;

cpu/efm32/periph/uart.c

@@ -26,8 +26,10 @@
 #include "periph/gpio.h"
 
 #include "em_usart.h"
+#include "em_usart_utils.h"
 #if LOW_POWER_ENABLED && defined(LEUART_COUNT) && LEUART_COUNT > 0
 #include "em_leuart.h"
+#include "em_leuart_utils.h"
 #endif
 
 /**
@@ -73,6 +75,11 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
         init.enable = usartDisable;
         init.baudrate = baudrate;
+#if EFM32_UART_MODES
+        init.databits = USART_DataBits2Def((uart_config[dev].mode >> 0) & 0xf);
+        init.stopbits = USART_StopBits2Def((uart_config[dev].mode >> 4) & 0xf);
+        init.parity = USART_Parity2Def((uart_config[dev].mode >> 8) & 0xf);
+#endif
 
         USART_InitAsync(uart, &init);
 
@@ -104,6 +111,11 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
         init.enable = leuartDisable;
         init.baudrate = baudrate;
+#if EFM32_UART_MODES
+        init.databits = LEUART_DataBits2Def((uart_config[dev].mode >> 0) & 0xf);
+        init.stopbits = LEUART_StopBits2Def((uart_config[dev].mode >> 4) & 0xf);
+        init.parity = LEUART_Parity2Def((uart_config[dev].mode >> 8) & 0xf);
+#endif
 
         LEUART_Init(leuart, &init);