UART: setting baudrate, stopbits, and parity on runtime

cpu/cc2538/periph/uart.c

@@ -348,3 +348,105 @@ void uart_poweroff(uart_t uart)
 {
     (void) uart;
 }
+
+int uart_mode(uart_t uart, uint8_t databits,
+    uint8_t stopbits, uart_parity_t parity)
+{
+    cc2538_uart_t *u;
+
+    switch (uart) {
+#if UART_0_EN
+        case UART_0:
+            u = UART_0_DEV;
+            break;
+#endif
+#if UART_1_EN
+        case UART_1:
+            u = UART_1_DEV;
+            break;
+#endif
+        default:
+            return -1;
+    }
+
+    /* flush TX buffer before mode switch */
+    uart_txflush(uart);
+
+    /* disable RX during mode switch */
+
+    u->cc2538_uart_ctl.CTLbits.RXE = 0;
+
+    switch(databits){
+        case 5:
+            u->cc2538_uart_lcrh.LCRHbits.WLEN = WLEN_5_BITS;
+            break;
+        case 6:
+            u->cc2538_uart_lcrh.LCRHbits.WLEN = WLEN_6_BITS;
+            break;
+        case 7:
+            u->cc2538_uart_lcrh.LCRHbits.WLEN = WLEN_7_BITS;
+            break;
+        case 8:
+            u->cc2538_uart_lcrh.LCRHbits.WLEN = WLEN_8_BITS;
+            break;
+        default:
+            u->cc2538_uart_ctl.CTLbits.RXE = 1;
+            return -2;
+    }
+
+    switch(stopbits){
+        case 1:
+            u->cc2538_uart_lcrh.LCRHbits.STP2 = 0;
+            break;
+        case 2:
+            u->cc2538_uart_lcrh.LCRHbits.STP2 = 1;
+            break;
+        default:
+            u->cc2538_uart_ctl.CTLbits.RXE = 1;
+            return -2;
+    }
+
+    switch(parity){
+        case UART_NONE:
+            u->cc2538_uart_lcrh.LCRHbits.EPS = 0;
+            u->cc2538_uart_lcrh.LCRHbits.PEN = 0;
+            break;
+        case UART_EVEN:
+            u->cc2538_uart_lcrh.LCRHbits.EPS = 1;
+            u->cc2538_uart_lcrh.LCRHbits.PEN = 1;
+            break;
+        case UART_ODD:
+            u->cc2538_uart_lcrh.LCRHbits.EPS = 0;
+            u->cc2538_uart_lcrh.LCRHbits.PEN = 1;
+            break;
+        default:
+            u->cc2538_uart_ctl.CTLbits.RXE = 1;
+            return -2;
+    }
+
+    u->cc2538_uart_ctl.CTLbits.RXE = 1;
+    return 0;
+}
+
+void uart_txflush(uart_t uart)
+{
+    cc2538_uart_t *u;
+
+    switch (uart) {
+#if UART_0_EN
+        case UART_0:
+            u = UART_0_DEV;
+            break;
+#endif
+#if UART_1_EN
+        case UART_1:
+            u = UART_1_DEV;
+            break;
+#endif
+        default:
+            return;
+    }
+
+    /* stupid busy waiting, could be improved... */
+    while(u->cc2538_uart_fr.FRbits.TXFE == 0);
+}

drivers/include/periph/uart.h

@@ -85,6 +85,17 @@ typedef unsigned int uart_t;
 #endif
 /** @} */
 
+/**
+ * @brief   Parity modes
+ * @{
+ */
+typedef enum {
+    UART_NONE,
+    UART_EVEN,
+    UART_ODD,
+} uart_parity_t;
+/** @} */
+
 /**
  * @brief   Signature for receive interrupt callback
  *
@@ -124,6 +135,8 @@ enum {
  * - no parity
  * - 1 stop bit
  * - baudrate as given
+ * If needed, data bits, stop bits, and parity can be changed with
+ * uart_mode() afterwards.
  *
  * If no callback parameter is given (rx_cb := NULL), the UART will be
  * initialized in TX only mode.
@@ -146,8 +159,11 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg);
  * @brief   Write data from the given buffer to the specified UART device
  *
  * This function is blocking, as it will only return after @p len bytes from the
- * given buffer have been send. The way this data is send is up to the
- * implementation: active waiting, interrupt driven, DMA, etc.
+ * given buffer have been written into the UARTs TX FIFO. It does not guarantee,
+ * that all data have already been sent by the UART when the function returns.
+ * If necessary, use uart_txflush() afterwards to wait until this is done. The
+ * way this data is send to the UART is up to the implementation: active
+ * waiting, interrupt driven, DMA, etc.
  *
  * @param[in] uart          UART device to use for transmission
  * @param[in] data          data buffer to send
@@ -170,6 +186,34 @@ void uart_poweron(uart_t uart);
  */
 void uart_poweroff(uart_t uart);
 
+/**
+ * @brief Configure UART mode
+ *
+ * This function reconfigures the UART mode (data bits, stop bits, parity).
+ * Before doing this, it waits until all data in the UART TX buffer have been
+ * sent out. During the mode change, the UART receive is disabled.
+ *
+ * @param[in] uart          the UART device to set parity mode
+ * @param[in] databits      number of databits
+ * @param[in] stopbits      number of stopbits
+ * @param[in] parity        parity mode
+ *
+ * @return                  0 on success
+ * @return                  -1 on invalid UART device
+ * @return                  -2 on inapplicable parity
+ */
+int uart_mode(uart_t uart, uint8_t databits,
+    uint8_t stopbits, uart_parity_t parity);
+
+/**
+ * @brief Flush UART TX buffer
+ *
+ * Block until TX buffer is empty and all bytes have been shifted out
+ *
+ * @param[in] uart          the UART device to flush
+ */
+void uart_txflush(uart_t uart);
+
 #ifdef __cplusplus
 }
 #endif