Internal Temp → Color

1#include <stdint.h>
2#include "inc/hw_memmap.h"
3#include "driverlib/sysctl.h"
4#include "driverlib/gpio.h"
5#include "driverlib/adc.h"
6 
7#define LED_ALL (GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3)
8#define PWM_STEPS 256
9 
10static void showColor(uint8_t r, uint8_t g, uint8_t b, uint32_t periods) {
11    volatile uint32_t p, i;
12    for (p = 0; p < periods; p++)
13        for (i = 0; i < PWM_STEPS; i++) {
14            uint8_t out = 0;
15            if (i < r) out |= GPIO_PIN_1;
16            if (i < g) out |= GPIO_PIN_3;
17            if (i < b) out |= GPIO_PIN_2;
18            GPIOPinWrite(GPIO_PORTF_BASE, LED_ALL, out);
19            SysCtlDelay(2);
20        }
21}
22 
23// Internal temperature sensor -> Celsius x10 (e.g. 253 = 25.3 C)
24static int32_t readTempC_x10(void) {
25    uint32_t buf[1];
26    ADCProcessorTrigger(ADC0_BASE, 1);
27    while (!ADCIntStatus(ADC0_BASE, 1, false)) {}
28    ADCIntClear(ADC0_BASE, 1);
29    ADCSequenceDataGet(ADC0_BASE, 1, buf);
30    return 1475 - (2475 * (int32_t)buf[0]) / 4096;       // datasheet formula
31}
32 
33int main(void) {
34    SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL |
35                   SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);
36 
37    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
38    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOF)) {}
39    GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, LED_ALL);
40 
41    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
42    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_ADC0)) {}
43    ADCSequenceConfigure(ADC0_BASE, 1, ADC_TRIGGER_PROCESSOR, 0);
44    ADCSequenceStepConfigure(ADC0_BASE, 1, 0,
45                             ADC_CTL_TS | ADC_CTL_IE | ADC_CTL_END);  // TS = internal sensor
46    ADCSequenceEnable(ADC0_BASE, 1);
47    ADCIntClear(ADC0_BASE, 1);
48 
49    while (1) {
50        int32_t t = readTempC_x10();
51        if (t < 200) t = 200;                            // 20 C -> blue
52        if (t > 400) t = 400;                            // 40 C -> red
53        int32_t lv = ((t - 200) * 255) / 200;            // 0..255
54        if (lv < 128) showColor(0, lv * 2, 255 - lv * 2, 40);
55        else          showColor((lv - 128) * 2, 255 - (lv - 128) * 2, 0, 40);
56    }
57}