/************************************************************************************ * drivers/serial/serial_io.c * * Copyright (C) 2007-2009, 2011, 2015 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ************************************************************************************/ /************************************************************************************ * Included Files ************************************************************************************/ #include #include #include #include #include #include /************************************************************************************ * Public Functions ************************************************************************************/ /************************************************************************************ * Name: uart_xmitchars * * Description: * This function is called from the UART interrupt handler when an interrupt * is received indicating that there is more space in the transmit FIFO. This * function will send characters from the tail of the xmit buffer while the driver * write() logic adds data to the head of the xmit buffer. * ************************************************************************************/ void uart_xmitchars(FAR uart_dev_t *dev) { uint16_t nbytes = 0; /* Send while we still have data in the TX buffer & room in the fifo */ while (dev->xmit.head != dev->xmit.tail && uart_txready(dev)) { /* Send the next byte */ uart_send(dev, dev->xmit.buffer[dev->xmit.tail]); nbytes++; /* Increment the tail index */ if (++(dev->xmit.tail) >= dev->xmit.size) { dev->xmit.tail = 0; } } /* When all of the characters have been sent from the buffer disable the TX * interrupt. * * Potential bug? If nbytes == 0 && (dev->xmit.head == dev->xmit.tail) && * dev->xmitwaiting == true, then disabling the TX interrupt will leave * the uart_write() logic waiting to TX to complete with no TX interrupts. * Can that happen? */ if (dev->xmit.head == dev->xmit.tail) { uart_disabletxint(dev); } /* If any bytes were removed from the buffer, inform any waiters there there is * space available. */ if (nbytes) { uart_datasent(dev); } } /************************************************************************************ * Name: uart_receivechars * * Description: * This function is called from the UART interrupt handler when an interrupt * is received indicating that are bytes available in the receive fifo. This * function will add chars to head of receive buffer. Driver read() logic will * take characters from the tail of the buffer. * ************************************************************************************/ void uart_recvchars(FAR uart_dev_t *dev) { FAR struct uart_buffer_s *rxbuf = &dev->recv; #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS unsigned int watermark; #endif unsigned int status; int nexthead = rxbuf->head + 1; uint16_t nbytes = 0; if (nexthead >= rxbuf->size) { nexthead = 0; } #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS /* Pre-calcuate the watermark level that we will need to test against. */ watermark = (CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK * rxbuf->size) / 100; #endif /* Loop putting characters into the receive buffer until there are no further * characters to available. */ while (uart_rxavailable(dev)) { bool is_full = (nexthead == rxbuf->tail); char ch; #ifdef CONFIG_SERIAL_IFLOWCONTROL #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS unsigned int nbuffered; /* How many bytes are buffered */ if (rxbuf->head >= rxbuf->tail) { nbuffered = rxbuf->head - rxbuf->tail; } else { nbuffered = rxbuf->size - rxbuf->tail + rxbuf->head; } /* Is the level now above the watermark level that we need to report? */ if (nbuffered >= watermark) { /* Let the lower level driver know that the watermark level has been * crossed. It will probably activate RX flow control. */ if (uart_rxflowcontrol(dev, nbuffered, true)) { /* Low-level driver activated RX flow control, exit loop now. */ break; } } #else /* Check if RX buffer is full and allow serial low-level driver to pause * processing. This allows proper utilization of hardware flow control. */ if (is_full) { if (uart_rxflowcontrol(dev, rxbuf->size, true)) { /* Low-level driver activated RX flow control, exit loop now. */ break; } } #endif #endif ch = uart_receive(dev, &status); /* If the RX buffer becomes full, then the serial data is discarded. This is * necessary because on most serial hardware, you must read the data in order * to clear the RX interrupt. An option on some hardware might be to simply * disable RX interrupts until the RX buffer becomes non-FULL. However, that * would probably just cause the overrun to occur in hardware (unless it has * some large internal buffering). */ if (!is_full) { /* Add the character to the buffer */ rxbuf->buffer[rxbuf->head] = ch; nbytes++; /* Increment the head index */ rxbuf->head = nexthead; if (++nexthead >= rxbuf->size) { nexthead = 0; } } } /* If any bytes were added to the buffer, inform any waiters there is new * incoming data available. */ if (nbytes) { uart_datareceived(dev); } }