Simple RTOS for Microchip Baseline and Midrange MCUs

by Isaac Marino Bavaresco

//==============================================================================
// SimpleRTOS - Very simple RTOS for Microchip(R) Baseline and Midrange uCs
// v1.00 (2008-09-23)
// isaacbavaresco@yahoo.com.br
//==============================================================================
/*
 Copyright (c) 2007-2008, Isaac Marino Bavaresco
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Neither the name of the author 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 AUTHOR ''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 AUTHOR 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.
*/
//==============================================================================
/*
    Notes:  - Works with Hi-Tech PICC v9.60PL2;

            - Assembler optimizations must be OFF for every file that implements
              task functions (it is better to have the task functions in one or
              more files with no standard functions, to minimize the un-optimized
              code length).

            - Every task function must have a call to the macro
              "TASK_INIT( <task function name> );" as the first statement;

            - Every function called directly or indirectly by more than one task
              must have a call to the macro "FUNC_INIT( <function name> );" as the
              first statement, unless it doesn't have any parameters nor automatic
              variables, or all paths through the call-graphs that it belongs have
              at least one function that calls "FUNC_INIT" before the function is
              called.

              Unfortunately this impose certain restrictions when using library
              functions, unless each library function is called from just one
              task, or it is present only in call-graphs that at least one
              function calls "FUNC_INIT" before the library function is called,
              or you rebuild the library adding the call to "FUNC_INIT" to the
              library functions that need it.

            - SimpleRTOS functions and macros that may cause a context switch
              (Eg: Yield, Sleep, DeleteTask (when deleting itself) and
              MutexTake ) must be called only directly inside the task function,
              never indirectly by other functions.


    TO DO:  - Find a way to reuse local variables of tasks that are never active
              at the same time.

            - Implement semaphores.

            - Implement priorities and slice length.

*/
//==============================================================================
// Set TAB width to 4 characters
//==============================================================================
//
//                           PIC16F648A
//
//              +-----------------U-----------------+
//              |                                   |
//        <-  ==|  1 RA2/AN2/Vref        AN1/RA1 18 |==  ->
//              |                                   |
//        <-  ==|  2 RA3/AN3/CMP1        AN0/RA0 15 |==  ->
//              |                                   |
//        <-  ==|  3 RA4/T0CKI/CMP2     OSC1/RA7 16 |== <x
//              |                                   |
//         -> ==|  4 RA5/!MCLR          OSC2/RA6 15 |==  x>
//              |                                   |
//            ==|  5 GND                     VCC 14 |==
//              |                                   |
//        <-  ==|  6 RB0/INT           T1OSI/RB7 13 |==  ->
//              |                                   |
//    RXD  -> ==|  7 RB1/RX/DT   T1CKI/T1OSO/RB6 12 |==  ->
//              |                                   |
//    TXD <-  ==|  8 RB2/TX/CK               RB5 11 |==  ->
//              |                                   |
//        <-  ==|  9 RB3/CCP1                RB4 10 |==  ->
//              |                                   |
//              +-----------------------------------+
//
//
//==============================================================================
#include <pic.h>
#include "SimpleRTOS.h"

void memcpy( const void *dst, const void *src, unsigned char len );
//==============================================================================
__CONFIG( CPD & PROTECT & BORDIS & LVPDIS & MCLRDIS & PWRTEN & WDTEN & HS );
//==============================================================================

extern volatile unsigned short TMR1     @ 0x00e;
extern volatile unsigned short CCPR1    @ 0x015;
//==============================================================================
#define CLOCK       20000000ul
#define BAUD_RATE      19200ul
#define TICK_RATE       1000ul
#define COUNTER_RATE     100ul
//==============================================================================
unsigned char bank1 SerialRXBuffer[32];
unsigned char       SerialRXLength  = 0;
unsigned char       SerialRXInsert  = 0;

unsigned char bank1 SerialTXBuffer[16];
unsigned char       SerialTXLength  = 0;
unsigned char       SerialTXRemove  = 0;

bit                 Overrun         = 0;
//==============================================================================
void interrupt ISR( void )
    {
    //--------------------------------------------------------------------------
    if( CCP1IF && CCP1IE )
        {
        Ticks++;
        CCP1IF  = 0;
        }
    //--------------------------------------------------------------------------
    if( RCIF && RCIE )
        {
        if( OERR )
            {
            CREN    = 0;
            CREN    = 1;
            Overrun = 1;
            }
        if( SerialRXLength < sizeof SerialRXBuffer )
            {
            SerialRXBuffer[SerialRXInsert] = RCREG;
            if( ++SerialRXInsert >= sizeof SerialRXBuffer )
                SerialRXInsert  = 0;
            SerialRXLength++;
            }
        else
            {
            (void)RCREG;
            Overrun = 1;
            }
        }
    //--------------------------------------------------------------------------
    if( TXIF && TXIE )
        {
        if( SerialTXLength != 0 )
            {
            TXREG   = SerialTXBuffer[SerialTXRemove];
            if( ++SerialTXRemove >= sizeof SerialTXBuffer )
                SerialTXRemove  = 0;
            if( --SerialTXLength == 0 )
                TXIE    = 0;
            }
        else
            TXIE    = 0;
        }
    //--------------------------------------------------------------------------
    }
//==============================================================================
// Receive one char from the UART. If there is no available char, returns -1.

short SerialReceive( void )
    {
    unsigned char c;

    if( SerialRXLength == 0 )
        return -1;
    GIE = 0;
    c = SerialRXBuffer[ ( SerialRXInsert - SerialRXLength ) & ( sizeof SerialRXBuffer - 1 ) ];
    SerialRXLength--;
    GIE = 1;
    return (unsigned short)c;
    }
//==============================================================================
bit SerialTransmit( unsigned char c )
    {
    // Needed because this function is called by more than one task.
    FUNC_INIT( SerialTransmit );

    if( SerialTXLength >= sizeof SerialTXBuffer )
        return 0;
    GIE     = 0;
    SerialTXBuffer[ ( SerialTXRemove + SerialTXLength ) & ( sizeof SerialTXBuffer - 1 ) ] = c;
    SerialTXLength++;
    TXIE    = 1;
    GIE     = 1;
    return 1;
    }
//==============================================================================
bit TransmitInProgress( void )
    {
    return SerialTXLength || ! TRMT ? 1 : 0;
    }
//==============================================================================
TS_Context Contexts[6]; // We will have a maximum of 6 simultaneously running tasks.
//==============================================================================
void MainTask( void );

void main( void )
    {
    CMCON   = 0x07;     // Comparators off.
    PORTA   = 0x00;     // All PORTA pins off.
    PORTB   = 0x06;
    TRISA   = 0xe0;
    TRISB   = 0x02;

    SPBRG   = CLOCK / ( 16ul * BAUD_RATE ) - 1;
    TXSTA   = 0x26;     // 0010 0110
    RCSTA   = 0x90;     // 1001 0000

    CCPR1   = CLOCK / (  4ul * TICK_RATE );
    CCP1CON = 0x0b;     // CCP1 in compare mode.
    TMR1    = 0;
    T1CON   = 0x01;     // Start TMR1.

    PIR1    = 0x00;     // Clear all interrupt flags.
    PIE1    = 0x34;     // Enable CCP1, UART RX and UART TX interrupts.
    INTCON  = 0xc0;     // Enable selected interrupts.

    // Initialize the contexts and the rest of the RTOS.
    InitRTOS( Contexts, sizeof Contexts / sizeof Contexts[0] );

    // Create just one task, it will create the others.
    CreateTask( MainTask );

    // From now, the RTOS will take over.
    StartRTOS();
    }
//==============================================================================