IR Remote

1#include <stdint.h>
2#include <stdbool.h>
3#include "inc/hw_memmap.h"
4#include "driverlib/sysctl.h"
5#include "driverlib/gpio.h"
6#include "driverlib/timer.h"
7 
8#define LED_ALL (GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3)
9#define IR_PORT GPIO_PORTB_BASE
10#define IR_PIN  GPIO_PIN_2   // PB2
11#define PWM_STEPS 256
12 
13static void showColor(uint8_t r, uint8_t g, uint8_t b, uint32_t periods) {
14    volatile uint32_t p, i;
15    for (p = 0; p < periods; p++)
16        for (i = 0; i < PWM_STEPS; i++) {
17            uint8_t out = 0;
18            if (i < r) out |= GPIO_PIN_1;
19            if (i < g) out |= GPIO_PIN_3;
20            if (i < b) out |= GPIO_PIN_2;
21            GPIOPinWrite(GPIO_PORTF_BASE, LED_ALL, out);
22            SysCtlDelay(2);
23        }
24}
25 
26// 0..255 -> a rainbow color
27static void wheel(uint8_t pos, uint8_t *r, uint8_t *g, uint8_t *b) {
28    if (pos < 85)       { *r = 255 - pos * 3; *g = pos * 3;       *b = 0; }
29    else if (pos < 170) { pos -= 85;  *r = 0; *g = 255 - pos * 3; *b = pos * 3; }
30    else                { pos -= 170; *r = pos * 3; *g = 0;       *b = 255 - pos * 3; }
31}
32 
33static int irLevel(void) { return GPIOPinRead(IR_PORT, IR_PIN) ? 1 : 0; }
34 
35// Wait while the pin stays at 'level'; return how long it stayed (us)
36static uint32_t waitWhile(int level) {
37    uint32_t start = TimerValueGet(TIMER0_BASE, TIMER_A);
38    uint32_t guard = 2000000;
39    while (irLevel() == level)
40        if (--guard == 0) break;
41    return (TimerValueGet(TIMER0_BASE, TIMER_A) - start) / 50;   // 50 MHz -> us
42}
43 
44// Line has just gone LOW -> decode one NEC frame. 1 = ok.
45static int irDecode(uint32_t *out) {
46    uint32_t d, i, code = 0;
47    d = waitWhile(0);                       // leader burst ~9 ms
48    if (d < 7000 || d > 11000) return 0;
49    d = waitWhile(1);                       // space ~4.5 ms (repeat = 2.25 ms -> reject)
50    if (d < 3000 || d > 6000) return 0;
51    for (i = 0; i < 32; i++) {
52        waitWhile(0);                       // ~560 us burst
53        uint32_t space = waitWhile(1);      // 560 us = 0, 1690 us = 1
54        code <<= 1;
55        if (space > 1000) code |= 1;
56    }
57    *out = code;
58    return 1;
59}
60 
61int main(void) {
62    uint8_t r = 0, g = 0, b = 0;            // current color (starts off)
63 
64    SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL |
65                   SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);
66 
67    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
68    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOF)) {}
69    GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, LED_ALL);
70 
71    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);           // IR output on PB2
72    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOB)) {}
73    GPIOPinTypeGPIOInput(IR_PORT, IR_PIN);
74 
75    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);          // free-running us timer
76    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_TIMER0)) {}
77    TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC_UP);
78    TimerLoadSet(TIMER0_BASE, TIMER_A, 0xFFFFFFFF);
79    TimerEnable(TIMER0_BASE, TIMER_A);
80 
81    while (1) {
82        if (irLevel() == 0) {                              // a frame may be starting
83            uint32_t code;
84            if (irDecode(&code)) {
85                wheel((uint8_t)(code % 256), &r, &g, &b);  // button -> color
86            }
87        }
88        showColor(r, g, b, 2);                             // hold color, keep polling
89    }
90}