pios_usart.c

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/* 
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 3 of the License, or 
 * (at your option) any later version.
 * 
 * This program 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 General Public License 
 * for more details.
 * 
 * You should have received a copy of the GNU General Public License along 
 * with this program; if not, see <http://www.gnu.org/licenses/>
 */

/* Project Includes */
#include "pios.h"

#if defined(PIOS_INCLUDE_USART)

#include <pios_usart_priv.h>

/* Provide a COM driver */
static void PIOS_USART_ChangeBaud(uintptr_t usart_id, uint32_t baud);
static void PIOS_USART_RegisterRxCallback(uintptr_t usart_id, pios_com_callback rx_in_cb, uintptr_t context);
static void PIOS_USART_RegisterTxCallback(uintptr_t usart_id, pios_com_callback tx_out_cb, uintptr_t context);
static void PIOS_USART_TxStart(uintptr_t usart_id, uint16_t tx_bytes_avail);
static void PIOS_USART_RxStart(uintptr_t usart_id, uint16_t rx_bytes_avail);

const struct pios_com_driver pios_usart_com_driver = {
        .set_baud   = PIOS_USART_ChangeBaud,
        .tx_start   = PIOS_USART_TxStart,
        .rx_start   = PIOS_USART_RxStart,
        .bind_tx_cb = PIOS_USART_RegisterTxCallback,
        .bind_rx_cb = PIOS_USART_RegisterRxCallback,
};

enum pios_usart_dev_magic {
        PIOS_USART_DEV_MAGIC = 0x11223344,
};

struct pios_usart_dev {
        enum pios_usart_dev_magic     magic;
        const struct pios_usart_cfg * cfg;

        pios_com_callback rx_in_cb;
        uintptr_t rx_in_context;
        pios_com_callback tx_out_cb;
        uintptr_t tx_out_context;

        uint32_t rx_dropped;
};

static bool PIOS_USART_validate(struct pios_usart_dev * usart_dev)
{
        return (usart_dev->magic == PIOS_USART_DEV_MAGIC);
}

static struct pios_usart_dev * PIOS_USART_alloc(void)
{
        struct pios_usart_dev * usart_dev;

        usart_dev = (struct pios_usart_dev *)PIOS_malloc(sizeof(*usart_dev));
        if (!usart_dev) return(NULL);

        memset(usart_dev, 0, sizeof(*usart_dev));
        usart_dev->magic = PIOS_USART_DEV_MAGIC;
        return(usart_dev);
}

/* Bind Interrupt Handlers
 *
 * Map all valid USART IRQs to the common interrupt handler
 * and provide storage for a 32-bit device id IRQ to map
 * each physical IRQ to a specific registered device instance.
 */
static void PIOS_USART_generic_irq_handler(uintptr_t usart_id);

static uintptr_t PIOS_USART_1_id;
void USART1_IRQHandler(void) __attribute__ ((alias ("PIOS_USART_1_irq_handler")));
static void PIOS_USART_1_irq_handler (void)
{
        PIOS_USART_generic_irq_handler (PIOS_USART_1_id);
}

static uintptr_t PIOS_USART_2_id;
void USART2_IRQHandler(void) __attribute__ ((alias ("PIOS_USART_2_irq_handler")));
static void PIOS_USART_2_irq_handler (void)
{
        PIOS_USART_generic_irq_handler (PIOS_USART_2_id);
}

static uintptr_t PIOS_USART_3_id;
void USART3_IRQHandler(void) __attribute__ ((alias ("PIOS_USART_3_irq_handler")));
static void PIOS_USART_3_irq_handler (void)
{
        PIOS_USART_generic_irq_handler (PIOS_USART_3_id);
}

int32_t PIOS_USART_Init(uintptr_t * usart_id, const struct pios_usart_cfg * cfg, struct pios_usart_params * params)
{
        PIOS_DEBUG_Assert(usart_id);
        PIOS_DEBUG_Assert(cfg);

        struct pios_usart_dev * usart_dev;

        usart_dev = (struct pios_usart_dev *) PIOS_USART_alloc();
        if (!usart_dev) goto out_fail;

        /* Bind the configuration to the device instance */
        usart_dev->cfg = cfg;

        /* Enable the USART Pins Software Remapping */
        if (usart_dev->cfg->remap) {
                GPIO_PinRemapConfig(usart_dev->cfg->remap, ENABLE);
        }

        /* Initialize the USART Rx and Tx pins */
        GPIO_Init(usart_dev->cfg->rx.gpio, (GPIO_InitTypeDef*)&usart_dev->cfg->rx.init);
        GPIO_Init(usart_dev->cfg->tx.gpio, (GPIO_InitTypeDef*)&usart_dev->cfg->tx.init);

        /* Enable USART clock */
        switch ((uint32_t)usart_dev->cfg->regs) {
        case (uint32_t)USART1:
                RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
                break;
        case (uint32_t)USART2:
                RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
                break;
        case (uint32_t)USART3:
                RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
                break;
        }
  
        /* Configure the USART */
        USART_Init(usart_dev->cfg->regs, (USART_InitTypeDef*)&params->init);
  
        *usart_id = (uintptr_t)usart_dev;

        /* Configure USART Interrupts */
        switch ((uint32_t)usart_dev->cfg->regs) {
        case (uint32_t)USART1:
                PIOS_USART_1_id = (uintptr_t)usart_dev;
                break;
        case (uint32_t)USART2:
                PIOS_USART_2_id = (uintptr_t)usart_dev;
                break;
        case (uint32_t)USART3:
                PIOS_USART_3_id = (uintptr_t)usart_dev;
                break;
        }
        NVIC_Init((NVIC_InitTypeDef*)&usart_dev->cfg->irq.init);
        USART_ITConfig(usart_dev->cfg->regs, USART_IT_RXNE, ENABLE);
        USART_ITConfig(usart_dev->cfg->regs, USART_IT_TXE,  ENABLE);
  
        /* Enable USART */
        USART_Cmd(usart_dev->cfg->regs, ENABLE);

        return(0);

out_fail:
        return(-1);
}

static void PIOS_USART_RxStart(uintptr_t usart_id, uint16_t rx_bytes_avail)
{
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        USART_ITConfig(usart_dev->cfg->regs, USART_IT_RXNE, ENABLE);
}
static void PIOS_USART_TxStart(uintptr_t usart_id, uint16_t tx_bytes_avail)
{
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        USART_ITConfig(usart_dev->cfg->regs, USART_IT_TXE, ENABLE);
}

static void PIOS_USART_ChangeBaud(uintptr_t usart_id, uint32_t baud)
{
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        USART_InitTypeDef USART_InitStructure;

        /* Adjust the baud rate */
        USART_InitStructure.USART_BaudRate = baud;

        /* Get current parameters */
        USART_InitStructure.USART_WordLength          = usart_dev->cfg->regs->CR1 &  (uint32_t)USART_CR1_M;
        USART_InitStructure.USART_Parity              = usart_dev->cfg->regs->CR1 & ((uint32_t)USART_CR1_PCE  | (uint32_t)USART_CR1_PS);
        USART_InitStructure.USART_StopBits            = usart_dev->cfg->regs->CR2 &  (uint32_t)USART_CR2_STOP;
        USART_InitStructure.USART_HardwareFlowControl = usart_dev->cfg->regs->CR3 & ((uint32_t)USART_CR3_CTSE | (uint32_t)USART_CR3_RTSE);
        USART_InitStructure.USART_Mode                = usart_dev->cfg->regs->CR1 & ((uint32_t)USART_CR1_TE   | (uint32_t)USART_CR1_RE) ;

        /* Write back the new configuration */
        USART_Init(usart_dev->cfg->regs, &USART_InitStructure);
}

static void PIOS_USART_RegisterRxCallback(uintptr_t usart_id, pios_com_callback rx_in_cb, uintptr_t context)
{
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        /* 
         * Order is important in these assignments since ISR uses _cb
         * field to determine if it's ok to dereference _cb and _context
         */
        usart_dev->rx_in_context = context;
        usart_dev->rx_in_cb = rx_in_cb;
}

static void PIOS_USART_RegisterTxCallback(uintptr_t usart_id, pios_com_callback tx_out_cb, uintptr_t context)
{
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        /* 
         * Order is important in these assignments since ISR uses _cb
         * field to determine if it's ok to dereference _cb and _context
         */
        usart_dev->tx_out_context = context;
        usart_dev->tx_out_cb = tx_out_cb;
}

static void PIOS_USART_generic_irq_handler(uintptr_t usart_id)
{
        PIOS_IRQ_Prologue();
        struct pios_usart_dev * usart_dev = (struct pios_usart_dev *)usart_id;

        bool valid = PIOS_USART_validate(usart_dev);
        PIOS_Assert(valid);

        /* Force read of dr after sr to make sure to clear error flags */
        volatile uint16_t sr = usart_dev->cfg->regs->SR;
        volatile uint8_t dr = usart_dev->cfg->regs->DR;

        /* Check if RXNE flag is set */
        bool rx_need_yield = false;
        if (sr & USART_SR_RXNE) {
                uint8_t byte = dr;
                if (usart_dev->rx_in_cb) {
                        uint16_t rc;
                        rc = (usart_dev->rx_in_cb)(usart_dev->rx_in_context, &byte, 1, NULL, &rx_need_yield);
                        if (rc < 1) {
                                /* Lost bytes on rx */
                                usart_dev->rx_dropped += 1;
                        }
                }
        }

        /* Check if TXE flag is set */
        bool tx_need_yield = false;
        if (sr & USART_SR_TXE) {
                if (usart_dev->tx_out_cb) {
                        uint8_t b;
                        uint16_t bytes_to_send;

                        bytes_to_send = (usart_dev->tx_out_cb)(usart_dev->tx_out_context, &b, 1, NULL, &tx_need_yield);

                        if (bytes_to_send > 0) {
                                /* Send the byte we've been given */
                                usart_dev->cfg->regs->DR = b;
                        } else {
                                /* No bytes to send, disable TXE interrupt */
                                USART_ITConfig(usart_dev->cfg->regs, USART_IT_TXE, DISABLE);
                        }
                } else {
                        /* No bytes to send, disable TXE interrupt */
                        USART_ITConfig(usart_dev->cfg->regs, USART_IT_TXE, DISABLE);
                }
        }
        PIOS_IRQ_Epilogue();
}

#endif