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readtemp.c
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readtemp.c
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////////////////////////////////////////////////////////////////////////////////
// Simple pi pico-based temperature station.
//
// author: R Elliot Meyer
// date: 2022
//
////////////////////////////////////////////////////////////////////////////////
#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "hardware/i2c.h"
// Defining the i2c parameters for the SHT40 Sensor
static int addr = 0x44;
#define I2C_PORT i2c1
// Base communication functions adapted from pico example scripts.
static void sht40_reset() {
// Two byte reset. First byte register, second byte data
uint8_t buf = 0x06;
i2c_write_blocking(I2C_PORT, 0x00, &buf, 1, false);
}
static void sht40_read_raw(int16_t *t_ticks, int16_t *rh_ticks) {
uint8_t buffer[6];
// Start reading registers from register 0xFD for 6 bytes
// 0xFD address measures T & H with high precision
uint8_t val = 0xFD;
i2c_write_blocking(I2C_PORT, addr, &val, 1, true); // true to keep master control of bus
sleep_ms(10);
i2c_read_blocking(I2C_PORT, addr, buffer, 6, false);
//printf("%u %u %u %u %u %u\n",buffer[0],
//buffer[1],buffer[2],buffer[3],buffer[4],buffer[5]);
*t_ticks = buffer[0]*256 + buffer[1];
*rh_ticks = buffer[3]*256 + buffer[4];
}
int main() {
stdio_init_all();
printf("Reading raw data from registers...\n");
i2c_init(I2C_PORT, 400 * 1000);
gpio_set_function(14, GPIO_FUNC_I2C);
gpio_set_function(15, GPIO_FUNC_I2C);
gpio_pull_down(14);
gpio_pull_down(15);
// Initalize the multi-color LED
const uint LED_PIN_B = 18;
const uint LED_PIN_G = 19;
const uint LED_PIN_R = 20;
int LED = 1;
if (LED) {
gpio_init(LED_PIN_B);
gpio_init(LED_PIN_G);
gpio_init(LED_PIN_R);
gpio_set_dir(LED_PIN_B, GPIO_OUT);
gpio_set_dir(LED_PIN_G, GPIO_OUT);
gpio_set_dir(LED_PIN_R, GPIO_OUT);
gpio_put(LED_PIN_B, 0);
gpio_put(LED_PIN_G, 0);
gpio_put(LED_PIN_R, 0);
}
sht40_reset();
uint16_t t_ticks, rh_ticks;
double temp, humid;
while (1) {
sht40_read_raw(&t_ticks, &rh_ticks);
//printf("%u %u\n", t_ticks, rh_ticks);
temp = -45 + (175*t_ticks)/65535.0;
humid = -6 + (125*rh_ticks)/65535.0;
if (humid > 100)
humid = 100;
else if (humid < 0)
humid = 0;
if (LED) {
if (temp >= 20.0f && temp < 21.0f) {
gpio_put(LED_PIN_B, 1);
gpio_put(LED_PIN_G, 1);
gpio_put(LED_PIN_R, 0);
} else if (temp >= 21.0f && temp <= 22.0f) {
gpio_put(LED_PIN_B, 0);
gpio_put(LED_PIN_G, 1);
gpio_put(LED_PIN_R, 0);
} else if (temp > 22.0f && temp <= 23.0f) {
gpio_put(LED_PIN_B, 0);
gpio_put(LED_PIN_G, 1);
gpio_put(LED_PIN_R, 1);
} else if (temp > 23.0f) {
gpio_put(LED_PIN_B, 0);
gpio_put(LED_PIN_G, 0);
gpio_put(LED_PIN_R, 1);
} else {
gpio_put(LED_PIN_B, 1);
gpio_put(LED_PIN_G, 0);
gpio_put(LED_PIN_R, 0);
}
}
printf("%.2f\t%.2f\n", temp, humid);
sleep_ms(30000);
}
return 0;
}