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/*
* FreeRTOS Kernel V10.2.1
* Copyright (C) 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
*
* 1 tab == 4 spaces!
*/
/* BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER.
*
* This is not a proper UART driver. It only supports one port, uses loopback
* mode, and is used to test interrupts that use the FreeRTOS API as part of
* a wider test suite. Nor is it intended to show an efficient implementation
* of a UART interrupt service routine as queues are used to pass individual
* characters one at a time!
*/
/* Standard includes. */
#include <stdlib.h>
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"
/* Demo application includes. */
#include "serial.h"
/* Misc. constants. */
#define serNO_BLOCK ( ( TickType_t ) 0 )
/* The queue used to hold received characters. */
static QueueHandle_t xRxedChars;
/* The queue used to hold characters waiting transmission. */
static QueueHandle_t xCharsForTx;
/*-----------------------------------------------------------*/
xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
{
unsigned long ulBaudRateCount;
/* Initialise the hardware. */
/* Generate the baud rate constants for the wanted baud rate. */
ulBaudRateCount = configCPU_CLOCK_HZ / ulWantedBaud;
portENTER_CRITICAL();
{
/* Create the queues used by the com test task. */
xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
xCharsForTx = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
/* Reset UART. */
UCA1CTL1 |= UCSWRST;
/* Use SMCLK. */
UCA1CTL1 = UCSSEL0 | UCSSEL1;
/* Setup baud rate low byte. */
UCA1BR0 = ( unsigned char ) ( ulBaudRateCount & ( unsigned long ) 0xff );
/* Setup baud rate high byte. */
ulBaudRateCount >>= 8UL;
UCA1BR1 = ( unsigned char ) ( ulBaudRateCount & ( unsigned long ) 0xff );
/* UCLISTEN sets loopback mode! */
UCA1STAT = UCLISTEN;
/* Enable interrupts. */
UCA1IE |= UCRXIE;
/* Take out of reset. */
UCA1CTL1 &= ~UCSWRST;
}
portEXIT_CRITICAL();
/* Note the comments at the top of this file about this not being a generic
UART driver. */
return NULL;
}
/*-----------------------------------------------------------*/
signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed char *pcRxedChar, TickType_t xBlockTime )
{
/* Get the next character from the buffer. Return false if no characters
are available, or arrive before xBlockTime expires. */
if( xQueueReceive( xRxedChars, pcRxedChar, xBlockTime ) )
{
return pdTRUE;
}
else
{
return pdFALSE;
}
}
/*-----------------------------------------------------------*/
signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed char cOutChar, TickType_t xBlockTime )
{
signed portBASE_TYPE xReturn;
/* Send the next character to the queue of characters waiting transmission,
then enable the UART Tx interrupt, just in case UART transmission has already
completed and switched itself off. */
xReturn = xQueueSend( xCharsForTx, &cOutChar, xBlockTime );
UCA1IE |= UCTXIE;
return xReturn;
}
/*-----------------------------------------------------------*/
/* The implementation of this interrupt is provided to demonstrate the use
of queues from inside an interrupt service routine. It is *not* intended to
be an efficient interrupt implementation. A real application should make use
of the DMA. Or, as a minimum, transmission and reception could use a simple
RAM ring buffer, and synchronise with a task using a semaphore when a complete
message has been received or transmitted. */
#pragma vector=USCI_A1_VECTOR
interrupt void prvUSCI_A1_ISR( void )
{
signed char cChar;
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
if( ( UCA1IFG & UCRXIFG ) != 0 )
{
/* Get the character from the UART and post it on the queue of Rxed
characters. */
cChar = UCA1RXBUF;
xQueueSendFromISR( xRxedChars, &cChar, &xHigherPriorityTaskWoken );
}
else if( ( UCA1IFG & UCTXIFG ) != 0 )
{
/* The previous character has been transmitted. See if there are any
further characters waiting transmission. */
if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
{
/* There was another character queued - transmit it now. */
UCA1TXBUF = cChar;
}
else
{
/* There were no other characters to transmit - disable the Tx
interrupt. */
UCA1IE &= ~UCTXIE;
}
}
__bic_SR_register_on_exit( SCG1 + SCG0 + OSCOFF + CPUOFF );
/* If writing to a queue caused a task to unblock, and the unblocked task
has a priority equal to or above the task that this interrupt interrupted,
then lHigherPriorityTaskWoken will have been set to pdTRUE internally within
xQueuesendFromISR(), and portEND_SWITCHING_ISR() will ensure that this
interrupt returns directly to the higher priority unblocked task.
THIS MUST BE THE LAST THING DONE IN THE ISR. */
portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
}
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