pikeyd165 – Blame information for rev 1
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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1 | office | 1 | // pwm.c |
| 2 | // |
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| 3 | // Example program for bcm2835 library |
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| 4 | // Shows how to use PWM to control GPIO pins |
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| 5 | // |
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| 6 | // After installing bcm2835, you can build this |
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| 7 | // with something like: |
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| 8 | // gcc -o pwm pwm.c -l bcm2835 |
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| 9 | // sudo ./pwm |
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| 10 | // |
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| 11 | // Or you can test it before installing with: |
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| 12 | // gcc -o pwm -I ../../src ../../src/bcm2835.c pwm.c |
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| 13 | // sudo ./pwm |
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| 14 | // |
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| 15 | // Connect an LED between GPIO18 (pin 12) and GND to observe the LED changing in brightness |
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| 16 | // |
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| 17 | // Author: Mike McCauley |
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| 18 | // Copyright (C) 2013 Mike McCauley |
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| 19 | // $Id: RF22.h,v 1.21 2012/05/30 01:51:25 mikem Exp $ |
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| 20 | |||
| 21 | #include <bcm2835.h> |
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| 22 | #include <stdio.h> |
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| 23 | |||
| 24 | // PWM output on RPi Plug P1 pin 12 (which is GPIO pin 18) |
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| 25 | // in alt fun 5. |
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| 26 | // Note that this is the _only_ PWM pin available on the RPi IO headers |
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| 27 | #define PIN RPI_GPIO_P1_12 |
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| 28 | // and it is controlled by PWM channel 0 |
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| 29 | #define PWM_CHANNEL 0 |
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| 30 | // This controls the max range of the PWM signal |
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| 31 | #define RANGE 1024 |
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| 32 | |||
| 33 | int main(int argc, char **argv) |
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| 34 | { |
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| 35 | if (!bcm2835_init()) |
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| 36 | return 1; |
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| 37 | |||
| 38 | // Set the output pin to Alt Fun 5, to allow PWM channel 0 to be output there |
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| 39 | bcm2835_gpio_fsel(PIN, BCM2835_GPIO_FSEL_ALT5); |
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| 40 | |||
| 41 | // Clock divider is set to 16. |
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| 42 | // With a divider of 16 and a RANGE of 1024, in MARKSPACE mode, |
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| 43 | // the pulse repetition frequency will be |
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| 44 | // 1.2MHz/1024 = 1171.875Hz, suitable for driving a DC motor with PWM |
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| 45 | bcm2835_pwm_set_clock(BCM2835_PWM_CLOCK_DIVIDER_16); |
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| 46 | bcm2835_pwm_set_mode(PWM_CHANNEL, 1, 1); |
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| 47 | bcm2835_pwm_set_range(PWM_CHANNEL, RANGE); |
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| 48 | |||
| 49 | // Vary the PWM m/s ratio between 1/RANGE and (RANGE-1)/RANGE |
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| 50 | // over the course of a a few seconds |
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| 51 | int direction = 1; // 1 is increase, -1 is decrease |
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| 52 | int data = 1; |
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| 53 | while (1) |
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| 54 | { |
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| 55 | if (data == 1) |
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| 56 | direction = 1; // Switch to increasing |
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| 57 | else if (data == RANGE-1) |
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| 58 | direction = -1; // Switch to decreasing |
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| 59 | data += direction; |
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| 60 | bcm2835_pwm_set_data(PWM_CHANNEL, data); |
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| 61 | bcm2835_delay(1); |
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| 62 | } |
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| 63 | |||
| 64 | bcm2835_close(); |
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| 65 | return 0; |
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| 66 | } |