00001 /* 00002 * "Copyright (c) 2008 Robert B. Reese, Bryan A. Jones, J. W. Bruce ("AUTHORS")" 00003 * All rights reserved. 00004 * (R. Reese, reese_AT_ece.msstate.edu, Mississippi State University) 00005 * (B. A. Jones, bjones_AT_ece.msstate.edu, Mississippi State University) 00006 * (J. W. Bruce, jwbruce_AT_ece.msstate.edu, Mississippi State University) 00007 * 00008 * Permission to use, copy, modify, and distribute this software and its 00009 * documentation for any purpose, without fee, and without written agreement is 00010 * hereby granted, provided that the above copyright notice, the following 00011 * two paragraphs and the authors appear in all copies of this software. 00012 * 00013 * IN NO EVENT SHALL THE "AUTHORS" BE LIABLE TO ANY PARTY FOR 00014 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT 00015 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE "AUTHORS" 00016 * HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 00017 * 00018 * THE "AUTHORS" SPECIFICALLY DISCLAIMS ANY WARRANTIES, 00019 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY 00020 * AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS 00021 * ON AN "AS IS" BASIS, AND THE "AUTHORS" HAS NO OBLIGATION TO 00022 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS." 00023 * 00024 * Please maintain this header in its entirety when copying/modifying 00025 * these files. 00026 * 00027 * 00028 */ 00029 #include "pic24_all.h" 00030 00038 #ifndef SQWAVE_PWHIGH 00039 #define SQWAVE_PWHIGH 2000 // desired PW High, in us 00040 #endif 00041 #ifndef SQWAVE_PERIOD 00042 #define SQWAVE_PERIOD 20000 // desired period, in us 00043 #endif 00044 00045 00046 void configTimer2(void) { 00047 T2CON = T2_OFF | T2_IDLE_CON | T2_GATE_OFF 00048 | T2_32BIT_MODE_OFF 00049 | T2_SOURCE_INT 00050 | T2_PS_1_64 ; //1 tick = 1.6 us at FCY=40 MHz 00051 PR2 = usToU16Ticks(SQWAVE_PERIOD, getTimerPrescale(T2CONbits)); 00052 TMR2 = 0; //clear timer2 value 00053 } 00054 00055 void configOutputCapture1(void) { 00056 T2CONbits.TON = 0; //disable Timer when configuring Output compare 00057 CONFIG_RB8_AS_DIG_OUTPUT(); 00058 CONFIG_OC1_TO_RP(8); //map OC1 to RP8/RP13 00059 //initialized the primary,secondary compare registers 00060 //assumes TIMER2 initialized before OC1 so PRE bits are set 00061 OC1R = 0; //go high when Timer2 == 0 00062 OC1RS = usToU16Ticks(SQWAVE_PWHIGH, getTimerPrescale(T2CONbits)); //go low when Timer2 == u16_sqwavePWHighTicks 00063 //turn on the compare toggle mode using Timer2 00064 OC1CON = OC_TIMER2_SRC | //Timer2 source 00065 OC_CONTINUE_PULSE; //Continuous pulse mode 00066 _OC1IF = 0; 00067 } 00068 00069 int main (void) { 00070 configBasic(HELLO_MSG); 00071 configTimer2(); 00072 configOutputCapture1(); 00073 T2CONbits.TON = 1; //turn on Timer2 to start sqwave 00074 while (1) doHeartbeat(); //nothing to do, squarewave generated in hardware 00075 }