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+/** @addtogroup usart_file
+
+@version 1.0.0
+
+@author @htmlonly &copy; @endhtmlonly 2009 Uwe Hermann <uwe@hermann-uwe.de>
+
+@date 30 August 2012
+
+This library supports the USART/UART in the STM32F series
+of ARM Cortex Microcontrollers by ST Microelectronics.
+
+Devices can have up to 3 USARTs and 2 UARTs.
+
+LGPL License Terms @ref lgpl_license
+ */
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**@{*/
+
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/stm32/rcc.h>
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Baudrate.
+
+The baud rate is computed from the APB high-speed prescaler clock (for USART1)
+or the APB low-speed prescaler clock (for other USARTs). These values must
+be correctly set before calling this function (refer to the rcc_clock_setup-*
+functions in RCC).
+
+@todo Add support for USART6 and oversampling in F2/F4
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] baud unsigned 32 bit. Baud rate specified in Hz.
+*/
+
+void usart_set_baudrate(u32 usart, u32 baud)
+{
+ u32 clock = rcc_ppre1_frequency;
+
+//#ifdef STM32F1
+ if (usart == USART1) {
+ clock = rcc_ppre2_frequency;
+ }
+/* This has to be added for F2 when it get's support for USART6 */
+/*
+#else
+ if ((usart == USART1) ||
+ (usart == USART6)) {
+ clock = rcc_ppre2_frequency;
+ }
+#endif
+*/
+
+ /*
+ * Yes it is as simple as that. The reference manual is
+ * talking about fractional calculation but it seems to be only
+ * marketting babble to sound awesome. It is nothing else but a
+ * simple divider to generate the correct baudrate.
+ *
+ * Note: We round() the value rather than floor()ing it, for more
+ * accurate divisor selection.
+ */
+ USART_BRR(usart) = ((2 * clock) + baud) / (2 * baud);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Word Length.
+
+The word length is set to 8 or 9 bits. Note that the last bit will be a parity bit
+if parity is enabled, in which case the data length will be 7 or 8 bits respectively.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] bits unsigned 32 bit. Word length in bits 8 or 9.
+*/
+
+void usart_set_databits(u32 usart, u32 bits)
+{
+ if (bits == 8)
+ USART_CR1(usart) &= ~USART_CR1_M; /* 8 data bits */
+ else
+ USART_CR1(usart) |= USART_CR1_M; /* 9 data bits */
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Stop Bit(s).
+
+The stop bits are specified as 0.5, 1, 1.5 or 2.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] stopbits unsigned 32 bit. Stop bits @ref usart_cr2_stopbits.
+*/
+
+void usart_set_stopbits(u32 usart, u32 stopbits)
+{
+ u32 reg32;
+
+ reg32 = USART_CR2(usart);
+ reg32 = (reg32 & ~USART_CR2_STOPBITS_MASK) | stopbits;
+ USART_CR2(usart) = reg32;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Parity.
+
+The parity bit can be selected as none, even or odd.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] parity unsigned 32 bit. Parity @ref usart_cr1_parity.
+*/
+
+void usart_set_parity(u32 usart, u32 parity)
+{
+ u32 reg32;
+
+ reg32 = USART_CR1(usart);
+ reg32 = (reg32 & ~USART_PARITY_MASK) | parity;
+ USART_CR1(usart) = reg32;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Rx/Tx Mode.
+
+The mode can be selected as Rx only, Tx only or Rx+Tx.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] mode unsigned 32 bit. Mode @ref usart_cr1_mode.
+*/
+
+void usart_set_mode(u32 usart, u32 mode)
+{
+ u32 reg32;
+
+ reg32 = USART_CR1(usart);
+ reg32 = (reg32 & ~USART_MODE_MASK) | mode;
+ USART_CR1(usart) = reg32;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Set Hardware Flow Control.
+
+The flow control bit can be selected as none, RTS, CTS or RTS+CTS.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] flowcontrol unsigned 32 bit. Flowcontrol @ref usart_cr3_flowcontrol.
+*/
+
+void usart_set_flow_control(u32 usart, u32 flowcontrol)
+{
+ u32 reg32;
+
+ reg32 = USART_CR3(usart);
+ reg32 = (reg32 & ~USART_FLOWCONTROL_MASK) | flowcontrol;
+ USART_CR3(usart) = reg32;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Enable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable(u32 usart)
+{
+ USART_CR1(usart) |= USART_CR1_UE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Disable.
+
+At the end of the current frame, the USART is disabled to reduce power.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable(u32 usart)
+{
+ USART_CR1(usart) &= ~USART_CR1_UE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Send a Data Word.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] data unsigned 16 bit.
+*/
+
+void usart_send(u32 usart, u16 data)
+{
+ /* Send data. */
+ USART_DR(usart) = (data & USART_DR_MASK);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Read a Received Data Word.
+
+If parity is enabled the MSB (bit 7 or 8 depending on the word length) is the parity bit.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@returns unsigned 16 bit data word.
+*/
+
+u16 usart_recv(u32 usart)
+{
+ /* Receive data. */
+ return USART_DR(usart) & USART_DR_MASK;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Wait for Transmit Data Buffer Empty
+
+Blocks until the transmit data buffer becomes empty and is ready to accept the
+next data word.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_wait_send_ready(u32 usart)
+{
+ /* Wait until the data has been transferred into the shift register. */
+ while ((USART_SR(usart) & USART_SR_TXE) == 0);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Wait for Received Data Available
+
+Blocks until the receive data buffer holds a valid received data word.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_wait_recv_ready(u32 usart)
+{
+ /* Wait until the data is ready to be received. */
+ while ((USART_SR(usart) & USART_SR_RXNE) == 0);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Send Data Word with Blocking
+
+Blocks until the transmit data buffer becomes empty then writes the next data word
+for transmission.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] data unsigned 16 bit.
+*/
+
+void usart_send_blocking(u32 usart, u16 data)
+{
+ usart_wait_send_ready(usart);
+ usart_send(usart, data);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Read a Received Data Word with Blocking.
+
+Wait until a data word has been received then return the word.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@returns unsigned 16 bit data word.
+*/
+
+u16 usart_recv_blocking(u32 usart)
+{
+ usart_wait_recv_ready(usart);
+
+ return usart_recv(usart);
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Receiver DMA Enable.
+
+DMA is available on:
+@li USART1 Rx DMA1 channel 5.
+@li USART2 Rx DMA1 channel 6.
+@li USART3 Rx DMA1 channel 3.
+@li UART4 Rx DMA2 channel 3.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable_rx_dma(u32 usart)
+{
+ USART_CR3(usart) |= USART_CR3_DMAR;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Receiver DMA Disable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable_rx_dma(u32 usart)
+{
+ USART_CR3(usart) &= ~USART_CR3_DMAR;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Transmitter DMA Enable.
+
+DMA is available on:
+@li USART1 Tx DMA1 channel 4.
+@li USART2 Tx DMA1 channel 7.
+@li USART3 Tx DMA1 channel 2.
+@li UART4 Tx DMA2 channel 5.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable_tx_dma(u32 usart)
+{
+ USART_CR3(usart) |= USART_CR3_DMAT;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Transmitter DMA Disable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable_tx_dma(u32 usart)
+{
+ USART_CR3(usart) &= ~USART_CR3_DMAT;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Receiver Interrupt Enable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable_rx_interrupt(u32 usart)
+{
+ USART_CR1(usart) |= USART_CR1_RXNEIE;
+}
+
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Receiver Interrupt Disable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable_rx_interrupt(u32 usart)
+{
+ USART_CR1(usart) &= ~USART_CR1_RXNEIE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Transmitter Interrupt Enable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable_tx_interrupt(u32 usart)
+{
+ USART_CR1(usart) |= USART_CR1_TXEIE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Transmitter Interrupt Disable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable_tx_interrupt(u32 usart)
+{
+ USART_CR1(usart) &= ~USART_CR1_TXEIE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Error Interrupt Enable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_enable_error_interrupt(u32 usart)
+{
+ USART_CR3(usart) |= USART_CR3_EIE;
+}
+
+/*-----------------------------------------------------------------------------*/
+/** @brief USART Error Interrupt Disable.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+*/
+
+void usart_disable_error_interrupt(u32 usart)
+{
+ USART_CR3(usart) &= ~USART_CR3_EIE;
+}
+
+/*---------------------------------------------------------------------------*/
+/** @brief USART Read a Status Flag.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] flag Unsigned int32. Status register flag @ref usart_sr_flags.
+@returns boolean: flag set.
+*/
+
+bool usart_get_flag(u32 usart, u32 flag)
+{
+ return ((USART_SR(usart) & flag) != 0);
+}
+
+/*---------------------------------------------------------------------------*/
+/** @brief USART Return Interrupt Source.
+
+Returns true if the specified interrupt flag (IDLE, RXNE, TC, TXE or OE) was
+set and the interrupt was enabled. If the specified flag is not an interrupt
+flag, the function returns false.
+
+@todo These are the most important interrupts likely to be used. Others
+relating to LIN break, and error conditions in multibuffer communication, need
+to be added for completeness.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref usart_reg_base
+@param[in] flag Unsigned int32. Status register flag @ref usart_sr_flags.
+@returns boolean: flag and interrupt enable both set.
+*/
+
+bool usart_get_interrupt_source(u32 usart, u32 flag)
+{
+u32 flag_set = (USART_SR(usart) & flag);
+/* IDLE, RXNE, TC, TXE interrupts */
+ if ((flag >= USART_SR_IDLE) && (flag <= USART_SR_TXE))
+ return ((flag_set & USART_CR1(usart)) != 0);
+/* Overrun error */
+ else if (flag == USART_SR_ORE)
+ return (flag_set && (USART_CR3(usart) & USART_CR3_CTSIE));
+ return (false);
+}
+
+/**@}*/
+