simple-FreeRTOS-demo/serial/serial.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
   3
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  24
  25     This file is part of the FreeRTOS distribution.
  26
  27     FreeRTOS is free software; you can redistribute it and/or modify it under
  28     the terms of the GNU General Public License (version 2) as published by the
  29     Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
  30     ***NOTE*** The exception to the GPL is included to allow you to distribute
  31     a combined work that includes FreeRTOS without being obliged to provide the
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  35     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
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  44     http://www.FreeRTOS.org - Documentation, latest information, license and
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  52 */
  53
  54 /*
  55         Changes from V2.4.0
  56
  57                 + Made serial ISR handling more complete and robust.
  58
  59         Changes from V2.4.1
  60
  61                 + Split serial.c into serial.c and serialISR.c.  serial.c can be
  62                   compiled using ARM or THUMB modes.  serialISR.c must always be
  63                   compiled in ARM mode.
  64                 + Another small change to cSerialPutChar().
  65
  66         Changed from V2.5.1
  67
  68                 + In cSerialPutChar() an extra check is made to ensure the post to
  69                   the queue was successful if then attempting to retrieve the posted
  70                   character.
  71
  72 */
  73
  74 /*
  75         BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR UART0.
  76
  77         This file contains all the serial port components that can be compiled to
  78         either ARM or THUMB mode.  Components that must be compiled to ARM mode are
  79         contained in serialISR.c.
  80 */
  81
  82 /* Standard includes. */
  83 #include <stdlib.h>
  84
  85 /* Scheduler includes. */
  86 #include "FreeRTOS.h"
  87 #include "queue.h"
  88 #include "task.h"
  89
  90 /* Demo application includes. */
  91 #include "serial.h"
  92
  93 /*-----------------------------------------------------------*/
  94
  95 /* Constants to setup and access the UART. */
  96 #define serDLAB                                                 ( ( unsigned char ) 0x80 )
  97 #define serENABLE_INTERRUPTS                    ( ( unsigned char ) 0x03 )
  98 #define serNO_PARITY                                    ( ( unsigned char ) 0x00 )
  99 #define ser1_STOP_BIT                                   ( ( unsigned char ) 0x00 )
 100 #define ser8_BIT_CHARS                                  ( ( unsigned char ) 0x03 )
 101 #define serFIFO_ON                                              ( ( unsigned char ) 0x01 )
 102 #define serCLEAR_FIFO                                   ( ( unsigned char ) 0x06 )
 103 #define serWANTED_CLOCK_SCALING                 ( ( unsigned long ) 16 )
 104
 105 /* Constants to setup and access the VIC. */
 106 #define serUART0_VIC_CHANNEL                    ( ( unsigned long ) 0x0006 )
 107 #define serUART0_VIC_CHANNEL_BIT                ( ( unsigned long ) 0x0040 )
 108 #define serUART0_VIC_ENABLE                             ( ( unsigned long ) 0x0020 )
 109 #define serCLEAR_VIC_INTERRUPT                  ( ( unsigned long ) 0 )
 110
 111 #define serINVALID_QUEUE                                ( ( xQueueHandle ) 0 )
 112 #define serHANDLE                                               ( ( xComPortHandle ) 1 )
 113 #define serNO_BLOCK                                             ( ( portTickType ) 0 )
 114
 115 /*-----------------------------------------------------------*/
 116
 117 /* Queues used to hold received characters, and characters waiting to be
 118 transmitted. */
 119 static xQueueHandle xRxedChars;
 120 static xQueueHandle xCharsForTx;
 121
 122 /*-----------------------------------------------------------*/
 123
 124 /* Communication flag between the interrupt service routine and serial API. */
 125 static volatile long *plTHREEmpty;
 126
 127 /*
 128  * The queues are created in serialISR.c as they are used from the ISR.
 129  * Obtain references to the queues and THRE Empty flag.
 130  */
 131 extern void vSerialISRCreateQueues(     unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx, long volatile **pplTHREEmptyFlag );
 132
 133 /*-----------------------------------------------------------*/
 134
 135 xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
 136 {
 137 unsigned long ulDivisor, ulWantedClock;
 138 xComPortHandle xReturn = serHANDLE;
 139 extern void ( vUART_ISR_Wrapper )( void );
 140
 141         /* The queues are used in the serial ISR routine, so are created from
 142         serialISR.c (which is always compiled to ARM mode. */
 143         vSerialISRCreateQueues( uxQueueLength, &xRxedChars, &xCharsForTx, &plTHREEmpty );
 144
 145         if(
 146                 ( xRxedChars != serINVALID_QUEUE ) &&
 147                 ( xCharsForTx != serINVALID_QUEUE ) &&
 148                 ( ulWantedBaud != ( unsigned long ) 0 )
 149           )
 150         {
 151                 portENTER_CRITICAL();
 152                 {
 153                         /* Setup the baud rate:  Calculate the divisor value. */
 154                         ulWantedClock = ulWantedBaud * serWANTED_CLOCK_SCALING;
 155                         ulDivisor = configCPU_CLOCK_HZ / ulWantedClock;
 156
 157                         /* Set the DLAB bit so we can access the divisor. */
 158                         UART0_LCR |= serDLAB;
 159
 160                         /* Setup the divisor. */
 161                         UART0_DLL = ( unsigned char ) ( ulDivisor & ( unsigned long ) 0xff );
 162                         ulDivisor >>= 8;
 163                         UART0_DLM = ( unsigned char ) ( ulDivisor & ( unsigned long ) 0xff );
 164
 165                         /* Turn on the FIFO's and clear the buffers. */
 166                         UART0_FCR = ( serFIFO_ON | serCLEAR_FIFO );
 167
 168                         /* Setup transmission format. */
 169                         UART0_LCR = serNO_PARITY | ser1_STOP_BIT | ser8_BIT_CHARS;
 170
 171                         /* Setup the VIC for the UART. */
 172                         VICIntSelect &= ~( serUART0_VIC_CHANNEL_BIT );
 173                         VICIntEnable |= serUART0_VIC_CHANNEL_BIT;
 174                         VICVectAddr1 = ( long ) vUART_ISR_Wrapper;
 175                         VICVectCntl1 = serUART0_VIC_CHANNEL | serUART0_VIC_ENABLE;
 176
 177                         /* Enable UART0 interrupts. */
 178                         UART0_IER |= serENABLE_INTERRUPTS;
 179                 }
 180                 portEXIT_CRITICAL();
 181         }
 182         else
 183         {
 184                 xReturn = ( xComPortHandle ) 0;
 185         }
 186
 187         return xReturn;
 188 }
 189 /*-----------------------------------------------------------*/
 190
 191 signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed char *pcRxedChar, portTickType xBlockTime )
 192 {
 193         /* The port handle is not required as this driver only supports UART0. */
 194         ( void ) pxPort;
 195
 196         /* Get the next character from the buffer.  Return false if no characters
 197         are available, or arrive before xBlockTime expires. */
 198         if( xQueueReceive( xRxedChars, pcRxedChar, xBlockTime ) )
 199         {
 200                 return pdTRUE;
 201         }
 202         else
 203         {
 204                 return pdFALSE;
 205         }
 206 }
 207 /*-----------------------------------------------------------*/
 208
 209 void vSerialPutString( xComPortHandle pxPort, const signed char * const pcString, unsigned short usStringLength )
 210 {
 211 signed char *pxNext;
 212
 213         /* NOTE: This implementation does not handle the queue being full as no
 214         block time is used! */
 215
 216         /* The port handle is not required as this driver only supports UART0. */
 217         ( void ) pxPort;
 218         ( void ) usStringLength;
 219
 220         /* Send each character in the string, one at a time. */
 221         pxNext = ( signed char * ) pcString;
 222         while( *pxNext )
 223         {
 224                 xSerialPutChar( pxPort, *pxNext, serNO_BLOCK );
 225                 pxNext++;
 226         }
 227 }
 228 /*-----------------------------------------------------------*/
 229
 230 signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed char cOutChar, portTickType xBlockTime )
 231 {
 232 signed portBASE_TYPE xReturn;
 233
 234         /* This demo driver only supports one port so the parameter is not used. */
 235         ( void ) pxPort;
 236
 237         portENTER_CRITICAL();
 238         {
 239                 /* Is there space to write directly to the UART? */
 240                 if( *plTHREEmpty == ( long ) pdTRUE )
 241                 {
 242                         /* We wrote the character directly to the UART, so was
 243                         successful. */
 244                         *plTHREEmpty = pdFALSE;
 245                         UART0_THR = cOutChar;
 246                         xReturn = pdPASS;
 247                 }
 248                 else
 249                 {
 250                         /* We cannot write directly to the UART, so queue the character.
 251                         Block for a maximum of xBlockTime if there is no space in the
 252                         queue. */
 253                         xReturn = xQueueSend( xCharsForTx, &cOutChar, xBlockTime );
 254
 255                         /* Depending on queue sizing and task prioritisation:  While we
 256                         were blocked waiting to post interrupts were not disabled.  It is
 257                         possible that the serial ISR has emptied the Tx queue, in which
 258                         case we need to start the Tx off again. */
 259                         if( ( *plTHREEmpty == ( long ) pdTRUE ) && ( xReturn == pdPASS ) )
 260                         {
 261                                 xQueueReceive( xCharsForTx, &cOutChar, serNO_BLOCK );
 262                                 *plTHREEmpty = pdFALSE;
 263                                 UART0_THR = cOutChar;
 264                         }
 265                 }
 266         }
 267         portEXIT_CRITICAL();
 268
 269         return xReturn;
 270 }
 271 /*-----------------------------------------------------------*/
 272
 273 void vSerialClose( xComPortHandle xPort )
 274 {
 275         /* Not supported as not required by the demo application. */
 276         ( void ) xPort;
 277 }
 278 /*-----------------------------------------------------------*/
 279
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