some learning code trying to use libopencm3 to read values from dht11 temperature sensor
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/*
* This file is part of the libopencm3 project.
*
* Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
*
* This library is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>
#include <SEGGER_RTT.h>
#define puts(s) SEGGER_RTT_WriteString(0, s);SEGGER_RTT_WriteString(0,"\n")
#define DHT_PORT GPIOB
#define DHT_PIN GPIO0
#define SEGMENT_PORT GPIOA
#define SEGMENT_A GPIO7
#define SEGMENT_B GPIO5
#define SEGMENT_C GPIO2
#define SEGMENT_D GPIO0
#define SEGMENT_E GPIO1
#define SEGMENT_F GPIO3
#define SEGMENT_G GPIO6
#define SEGMENT_DOT GPIO4
#define SEGMENT_ALL GPIO0 | GPIO1 | GPIO2 | GPIO3 | GPIO4 | GPIO5 | GPIO6 | GPIO7 | GPIO4
#define COMMON_PORT GPIOB
#define COMMON_ALL GPIO15 | GPIO14 | GPIO13 | GPIO12 | GPIO11
#define COMMON_1 GPIO15
#define COMMON_2 GPIO14
#define COMMON_3 GPIO13
#define COMMON_4 GPIO12
#define COMMON_L GPIO11
const uint16_t segment_numbers[] = {
SEGMENT_A | SEGMENT_B | SEGMENT_C | SEGMENT_D | SEGMENT_E | SEGMENT_F, // 0
SEGMENT_B | SEGMENT_C, // 1
SEGMENT_A | SEGMENT_B | SEGMENT_D | SEGMENT_E | SEGMENT_G, // 2
SEGMENT_A | SEGMENT_B | SEGMENT_C | SEGMENT_D | SEGMENT_G, // 3
SEGMENT_B | SEGMENT_C | SEGMENT_F | SEGMENT_G, // 4
SEGMENT_A | SEGMENT_C | SEGMENT_D | SEGMENT_F | SEGMENT_G, // 5
SEGMENT_A | SEGMENT_C | SEGMENT_D | SEGMENT_E | SEGMENT_F | SEGMENT_G, // 6
SEGMENT_A | SEGMENT_B | SEGMENT_C, // 7
SEGMENT_A | SEGMENT_B | SEGMENT_C | SEGMENT_D | SEGMENT_E | SEGMENT_F | SEGMENT_G, // 8
SEGMENT_A | SEGMENT_B | SEGMENT_C | SEGMENT_D | SEGMENT_F | SEGMENT_G, // 9
SEGMENT_A | SEGMENT_B | SEGMENT_C | SEGMENT_E | SEGMENT_F | SEGMENT_G, // A 10
SEGMENT_C | SEGMENT_D | SEGMENT_E | SEGMENT_F | SEGMENT_G, // B 11
SEGMENT_A | SEGMENT_D | SEGMENT_E | SEGMENT_F, // C 12
SEGMENT_B | SEGMENT_C | SEGMENT_D | SEGMENT_E | SEGMENT_G, // D 13
SEGMENT_A | SEGMENT_D | SEGMENT_E | SEGMENT_F | SEGMENT_G, // E 14
SEGMENT_A | SEGMENT_E | SEGMENT_F | SEGMENT_G, // F 15
SEGMENT_B | SEGMENT_C | SEGMENT_E | SEGMENT_F | SEGMENT_G, // H 16
SEGMENT_G // - 17
};
const uint16_t common_numbers[] = { COMMON_1, COMMON_2, COMMON_3, COMMON_4 };
volatile int segment_values[] = {17, 17, 17, 17};
volatile int common_counter = 0;
enum DHT11_STATE {
DHT11_STOP, // Stop statemachine
DHT11_START, // We drive DATA Low for minimum 18ms and then drive it HIGH and start waiting for response
DHT11_RESPONSE, // Wait for DHT to drive DATA Low
DHT11_DATA, // Receiving data
DHT11_END, // Got last bit
DHT11_TIMEOUT, // Not response or got partial data only
};
int g_dht11_state = DHT11_STOP;
// 2 pulses are the DHT Response and last 40 are data pulses for 5 bytes
// so we have total of 42 pulses
#define DHT11_BIT_COUNT 42
int g_dht_i = 0; // how many bits we have captured
uint16_t g_dht_vals[DHT11_BIT_COUNT] = {0}; // captured bit times in us
static void delay(int count)
{
for (int i=0; i < count; i++) {
__asm__("nop");
}
}
static void gpio_setup(void)
{
/* Enable GPIOA clock. */
/* Manually: */
// RCC_APB2ENR |= RCC_APB2ENR_IOPCEN;
/* Using API functions: */
rcc_periph_clock_enable(RCC_GPIOA);
rcc_periph_clock_enable(RCC_GPIOB);
/* Set GPIO5 (in GPIO port A) to 'output push-pull'. */
/* Manually: */
// GPIOA_CRH = (GPIO_CNF_OUTPUT_PUSHPULL << (((5 - 8) * 4) + 2));
// GPIOA_CRH |= (GPIO_MODE_OUTPUT_2_MHZ << ((5 - 8) * 4));
/* Using API functions: */
// DHT Data pin
gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, DHT_PIN);
// Maple mini led
gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO1);
// A random DEBUG pin we can toggle and measure with logic
gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO2);
// 7segments
gpio_set_mode(SEGMENT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, SEGMENT_ALL);
// commons
gpio_set_mode(COMMON_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, COMMON_ALL);
}
// Onetime config of timer things that stay the same
static void tim_setup(void)
{
// 7 segment driver timer
nvic_enable_irq(NVIC_TIM2_IRQ);
nvic_set_priority(NVIC_TIM2_IRQ, 2);
rcc_periph_clock_enable(RCC_TIM2);
rcc_periph_reset_pulse(RST_TIM2);
timer_set_mode(TIM2, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
timer_set_prescaler(TIM2, (rcc_apb1_frequency*2) / 1000000 - 1); // set timer tickrate to 1mhz
timer_set_period(TIM2, 2000); // 2ms
timer_enable_irq(TIM2, TIM_DIER_UIE);
// start displaying 7 segment numbers
timer_enable_counter(TIM2);
// DHT11 Reading timer
nvic_enable_irq(NVIC_TIM3_IRQ);
nvic_set_priority(NVIC_TIM3_IRQ, 1);
rcc_periph_clock_enable(RCC_TIM3);
rcc_periph_reset_pulse(RST_TIM3);
// configure the timer to be a normal up counting timer, nothing fancy
timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
timer_set_prescaler(TIM3, (rcc_apb1_frequency*2) / 1000000 - 1); // set timer tickrate to 1mhz
timer_set_period(TIM3, 0xffff); // ~64 ms, DHT11 packet is never longer than 26ms
timer_enable_irq(TIM3, TIM_DIER_UIE); // overflow
timer_enable_irq(TIM3, TIM_DIER_CC3IE); // triggered when DHT drives DATA pin
// timer is enabled in dht_start()
}
static void show_segment_value(int common, int value, bool decimal) {
gpio_clear(COMMON_PORT, COMMON_ALL);
gpio_set(SEGMENT_PORT, SEGMENT_ALL);
gpio_clear(SEGMENT_PORT, segment_numbers[value] | (decimal ? SEGMENT_DOT : 0));
gpio_set(COMMON_PORT, common_numbers[common]);
}
void tim2_isr(void) {
if (timer_get_flag(TIM2, TIM_SR_UIF)) {
timer_clear_flag(TIM2, TIM_SR_UIF);
show_segment_value(common_counter, segment_values[common_counter],
common_counter == 1 ? true : false);
common_counter++;
if (common_counter > 3){
common_counter = 0;
}
}
}
void tim3_isr(void)
{
// Timer overflow that should only happen if DHT11 does not answer
if (timer_get_flag(TIM3, TIM_SR_UIF)) {
timer_clear_flag(TIM3, TIM_SR_UIF);
puts("overflow");
g_dht11_state = DHT11_TIMEOUT;
timer_disable_counter(TIM3);
}
else if (timer_get_flag(TIM3, TIM_SR_CC3IF)) // PB0 changed value
{
//gpio_toggle(GPIOB, GPIO2);
// handle DHT11_END_START
if (g_dht11_state == DHT11_START) {
// Drive DATA pin high for a split second so that we have a nice sharp edge
gpio_set(DHT_PORT, DHT_PIN);
// Make the GPIO input so that we can wait for response
// there is a external pull-up connected to the DATA pin
// probably could use the internal pull-up also...
gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, DHT_PIN);
// setup timer input capture to wait for start response from dht11
// need to disable input capture before we can configure it.
timer_ic_disable(TIM3, TIM_IC3);
timer_ic_set_input(TIM3, TIM_IC3, TIM_IC_IN_TI3);
timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_FALLING);
timer_clear_flag(TIM3, TIM_SR_CC3IF); // otherwise we will get a invalid interrupt
timer_ic_enable(TIM3, TIM_IC3);
//puts("waiting for response");
g_dht11_state = DHT11_RESPONSE;
}
// DHT11 drove DATA low and has started talking to us
else if (g_dht11_state == DHT11_RESPONSE) {
// store time when DHT11 pulled DATA low
g_dht_vals[g_dht_i++] = TIM_CCR3(TIM3);
g_dht11_state = DHT11_DATA;
}
// DHT11 is sending data to us
else {
// store length of the data bit
g_dht_vals[g_dht_i++] = TIM_CCR3(TIM3);
}
// Did we just capture our last bit?
if (g_dht_i >= DHT11_BIT_COUNT) {
// yes we did
g_dht11_state = DHT11_END;
timer_disable_counter(TIM3);
}
timer_clear_flag(TIM3, TIM_SR_CC3IF);
//gpio_toggle(GPIOB, GPIO2);
}
// Should only happen if TIM_SR_CC3IF is too slow
// at 72mhz it should never happen but could at lower cpu speeds
if (timer_get_flag(TIM3, TIM_SR_CC3OF))
{
timer_clear_flag(TIM3, TIM_SR_CC3OF);
//puts("we are too slow to read and clear timer input capture flags");
g_dht11_state = DHT11_TIMEOUT;
timer_disable_counter(TIM3);
}
}
// Setup the timer and trigger DHT11 Start
static void dht_start(void)
{
timer_disable_counter(TIM3);
g_dht11_state = DHT11_STOP;
g_dht_i = 0;
// Setup DHT11_END_START trigger on output compare 1
timer_set_counter(TIM3, 0);
// capture compare channel must be disabled before we can configure it
timer_ic_disable(TIM3, TIM_IC3);
// set channel as output so that we can get an interrupt when OC3 values matches the timer counter
timer_ic_set_input(TIM3, TIM_IC3, TIM_IC_OUT);
// tick rate should be 1Mhz (via timer prescaler), so this should trigger in 20ms
timer_set_oc_value(TIM3, TIM_OC3, 1000*20);
// clear status flags so that we dont get any stray interrupts
timer_clear_flag(TIM3, TIM_SR_CC3IF);
// and make sure that we can get interrupts
timer_ic_enable(TIM3, TIM_IC3);
// Begin the statemachine
g_dht11_state = DHT11_START;
// Do DHT11_BEGIN_START aka drive DATA Low
gpio_set_mode(DHT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, DHT_PIN);
gpio_clear(DHT_PORT, DHT_PIN);
// And start counting
timer_enable_counter(TIM3);
}
// Parse received DHT11 bit timing data from g_dht_vals and print out pretty values
static void dht_parse_data(void) {
int8_t data[5] = {0};
uint8_t checksum = 0;
int data_index = 0;
int data_bit = 7;
// create bytes from bits
for (int i=2; i < DHT11_BIT_COUNT; i++){ // First 2 pulses are start of response, ignore them
uint16_t bit_time = g_dht_vals[i] - g_dht_vals[i-1];
// ~80us is 0 and ~120us is 1
if (bit_time > 100) {
data[data_index] |= 1 << data_bit;
}
data_bit--;
if (data_bit < 0) {
data_bit = 7;
data_index++;
}
}
for (int i = 0; i < 4; i++){
checksum += data[i];
}
if (checksum == data[4]) {
SEGGER_RTT_printf(0, "Humidity: %d.%d%%; Temperature: %d.%dC\n",
data[0], data[1], data[2], data[3]);
if (segment_values[3] == 0xC) {
segment_values[3] = 16; // now showing humidity
segment_values[0] = (data[0] / 10) % 10;
segment_values[1] = data[0] % 10;
segment_values[2] = data[1] % 10;
} else {
segment_values[3] = 0xC; // now showing temperature
segment_values[0] = (data[2] / 10) % 10;
segment_values[1] = data[2] % 10;
segment_values[2] = data[3] % 10;
}
} else {
SEGGER_RTT_printf(0, "Checksum did not match, %x != %x\n", checksum, data[4]);
}
}
// Just toggle the data pin, used only for debugging
//static void dht_start_signal(void)
//{
// gpio_set_mode(DHT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, DHT_PIN);
// gpio_clear(DHT_PORT, DHT_PIN);
// delay(100000);
// //delay(30000);
// gpio_set(DHT_PORT, DHT_PIN);
// delay(100);
// gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, DHT_PIN);
//}
int main(void)
{
int i = 0;
bool wait = false;
puts("Start");
rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
gpio_setup();
tim_setup();
/* Blink the LED (PA5) on the board. */
while (1) {
/* Using API function gpio_toggle(): */
//gpio_toggle(GPIOB, GPIO1); /* LED on/off */
SEGGER_RTT_printf(0, "Poll: %d, seg: %d\n", i, i & 0xf);
//show_segment_value(i & 3, 16, false);
i++;
delay(10000000);
//delay(1000000);
dht_start();
wait = true;
while (wait) {
switch (g_dht11_state) {
case DHT11_END:
dht_parse_data();
// fall through
case DHT11_TIMEOUT:
wait = false;
}
}
}
return 0;
}