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  1. I'm playing around with timer interrupts on the DP32 using Arduino and the ChipKIT Core. I was surprised to find out that this involves register manipulation. So I can set up timers using register manipulation in Arduino, but I can't seem to do anything else with register manipulation. For example, here is some code of mine which should set up a PWM signal on pin 13 (OC4) of the DP32 using register manipulation, instead of analogWrite() function. Problem is that it doesn't work and I can't figure out why. This problem is exacerbated by the apparent lack of documentation on any of the register manipulation functions(?) that I use to set my timers up previously. I know they work, but I only found them in a tutorial that doesn't explain where they come from, or much about them at all. So I have the following questions: Am I allowed to do register manipulation for more than just timers? Where can I find more information about how ChipKIT Core uses and defines these things? What am I doing wrong with my code? /******************************** Constants ********************************/ #define T3CON_ENABLE_BIT 0x8000 #define T3CON_PRESCALER_BITS 0x0070 #define T3_SOURCE_INT 0 #define OC4_ENABLE_BIT 0x8000 #define OC4_TIMER_SEL_BIT 0x0008 #define OC4_MODE_BITS 0x0007 #define OC4_MODE_PWM_SET 0x0006 // Prescaler values // Don't change these. Set the prescaler below using these. #define T3_PRESCALE_1_1 0 #define T3_PRESCALE_1_2 1 #define T3_PRESCALE_1_4 2 #define T3_PRESCALE_1_8 3 #define T3_PRESCALE_1_16 4 #define T3_PRESCALE_1_32 5 #define T3_PRESCALE_1_64 6 #define T3_PRESCALE_1_256 7 // Set the prescaler value we want to use #define PRESCALE T3_PRESCALE_1_256 // Current it's set to 1:256 // The DP32 runs at 40 MHz // The uC32 and WF32 run at 80 MHz #define CLOCK_FREQ 40000000 // Right now we're set for the DP32 // Set our target frequency // This is the frequency that our interrupt will run at in Hz #define T3_FREQUENCY 5 void setup() { uint32_t period; uint32_t cycle; uint32_t mask; // Disable everything T3CONCLR = T3CON_ENABLE_BIT; // Turn the timer off OC4CONCLR = OC4_ENABLE_BIT; // Turn OC4 off RPB2R = 0b0101; // Calculate the period we need for our given frequency if (PRESCALE == 7) period = 256; // 1:256 is a special case else period = 1 << PRESCALE; period = period * T3_FREQUENCY; period = CLOCK_FREQ / period; // Set up our timer T3CONCLR = T3CON_PRESCALER_BITS; // Clear the old prescaler mask = PRESCALE << 4; // Shift our new prescaler mask = mask | T3CON; // Mask our prescaler T3CON = mask; // Set the prescaler TMR3 = 0; // Clear the counter PR3 = period; // Set the period // Calculate our cycle cycle = period /2; // We want a 50% duty cycle // Set up our output compare OC4CONSET = OC4_TIMER_SEL_BIT; // Select timer 3 for source OC4CONCLR = OC4_MODE_BITS; // Clear our mode pins OC4CONSET = OC4_MODE_PWM_SET; // Set our mode to PWM w/out fault pin OC4R = cycle; // Set our cycle // Enable everything T3CONSET = T3CON_ENABLE_BIT; // Turn the timer on OC4CONSET = OC4_ENABLE_BIT; // Turn OC4 on } void loop() { }