pwm example

README.pwm

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+README.pwm
+
+this example demonstrates how to setup the LPC810 SCT function to generate a PWM signal.
+The led (pio0_2) is used to output the PWM signal visually.
+The input pin pio0_1 (ISP-button on LPC800 minikit) allows to change the duty cycle.
+
+

src/pwm.c

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+/**************************************************************************/
+/*!
+    @file     pwm.c
+
+    @section LICENSE
+
+    Software License Agreement (BSD License)
+
+    Copyright (c) 2014, Mat Kattanek
+    All rights reserved.
+
+    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 of the copyright holders 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 ''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 HOLDER 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.
+*/
+
+/**************************************************************************/
+
+/*
+    @info
+    setup SCT as 32bit timer.
+    generate PWM depending on match0 (period) and match1 (duty cycle) register.
+    using pio0_2 to flash led.
+ */
+
+#include <stdio.h>
+#include "LPC8xx.h"
+#include "gpio.h"
+#include "mrt.h"
+#include "uart.h"
+
+extern void configurePins();       // main.c
+
+#define ISP_BUTTON      (1)
+
+#define MATCH_PERIOD (SystemCoreClock/2)   // 2hz
+#define MATCH_DUTY   (SystemCoreClock/20)  // 10% duty cycle
+
+void
+sct_fsm_init (void)
+{
+  LPC_SCT->CONFIG = (LPC_SCT->CONFIG & ~0x00060001) | 0x00000001;   // UNIFIED  32bit
+
+  //--- MATCH/CAPTURE registers
+  LPC_SCT->REGMODE_L = 0x0000;           // L: 2x MATCH, 0x CAPTURE, 3 unused
+  LPC_SCT->MATCH[0].U = MATCH_PERIOD;    // MATCH0
+  LPC_SCT->MATCHREL[0].U = MATCH_PERIOD;
+  LPC_SCT->MATCH[1].U = MATCH_DUTY;      // MATCH1
+  LPC_SCT->MATCHREL[1].U = MATCH_DUTY;
+
+  //--- OUTPUT registers
+  LPC_SCT->OUT[0].SET = 0x00000001;      // Output_pin_0 set on event0
+  LPC_SCT->OUT[0].CLR = 0x00000002;      //              clear on event1
+  LPC_SCT->OUT[1].SET = 0;               // Unused outputs must not be affected by any event
+  LPC_SCT->OUT[1].CLR = 0;
+  LPC_SCT->OUT[2].SET = 0;
+  LPC_SCT->OUT[2].CLR = 0;
+  LPC_SCT->OUT[3].SET = 0;
+  LPC_SCT->OUT[3].CLR = 0;
+
+  //--- EVENT registers
+  LPC_SCT->EVENT[0].CTRL = 0x00005000;    // L: --> state L_ENTRY
+  LPC_SCT->EVENT[0].STATE = 0x00000001;
+  LPC_SCT->EVENT[1].CTRL = 0x00005001;    // L: --> state L_ENTRY
+  LPC_SCT->EVENT[1].STATE = 0x00000001;
+  LPC_SCT->EVENT[2].STATE = 0;            // Unused events must not have any effect
+  LPC_SCT->EVENT[3].STATE = 0;
+  LPC_SCT->EVENT[4].STATE = 0;
+  LPC_SCT->EVENT[5].STATE = 0;
+
+  //--- STATE registers
+  LPC_SCT->STATE_L = 0;
+  LPC_SCT->STATE_H = 0;
+
+  //--- CORE registers
+  LPC_SCT->START_L = 0x0000;
+  LPC_SCT->STOP_L =  0x0000;
+  LPC_SCT->HALT_L =  0x0000;
+  LPC_SCT->LIMIT_L = 0x0001;
+  LPC_SCT->START_H = 0x0000;
+  LPC_SCT->STOP_H =  0x0000;
+  LPC_SCT->HALT_H =  0x0000;
+  LPC_SCT->LIMIT_H = 0x0000;
+  LPC_SCT->EVEN =    0x00000000;
+}
+
+#if 0
+
+//
+// To activate the pwm main() function you need to rename
+//  the main() in main.c
+//
+
+int
+main(void)
+{
+  gpioInit();                            // Initialize the GPIO block
+
+  uart0Init(115200);                     // Initialize uart for printf output
+
+  mrtInit(__SYSTEM_CLOCK/1000);          // Configure the multi-rate timer for 1ms ticks
+
+  configurePins();                       // Configure the switch matrix (setup pins UART and GPIO)
+
+  LPC_SWM->PINASSIGN6 = 0x02FFFFFF;            // SCT OUTP_0 at P0.2 (led) on switch matrix
+  LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 8);       // enable the SCT clock
+
+  sct_fsm_init();                              // Initialize SCT
+  LPC_SCT->CTRL_L &= ~(1<<2);                  // unhalt the SCT by clearing bit 2 in CTRL
+
+  LPC_GPIO_PORT->DIR0 &= ~(1 << ISP_BUTTON);   // enable ISP button as input pin
+
+  while(1) {
+
+     mrtDelay(500);                                         //take a snooze
+
+     if ( (LPC_GPIO_PORT->PIN0 & 0x02) == 0) {	            // pio0_1 ISP button pushed?
+  	     if (LPC_SCT->MATCHREL[1].U < MATCH_PERIOD ) {
+           LPC_SCT->MATCHREL[1].U += MATCH_DUTY;            // increase duty cycle
+  	     }
+  	     else {
+           LPC_SCT->MATCHREL[1].U = 0;                      // rollover
+  	     }
+     }
+
+    // Send some text (redirected to UART)
+    printf("Hello, lpc810.pwm! dutycycle=%u \r\n", LPC_SCT->MATCHREL[1].U );
+  }
+}
+#endif

tools/LPC810_pwm.hex

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