Add DHT22 PIO reader and simplify display output

2026-10-26 09:33:32 +03:00 · 2026-05-02 20:00:57 +03:00
parent c5f2eebd2f
commit 63d7742e62
5 changed files with 172 additions and 26 deletions
@@ -0,0 +1,90 @@
+#include "dht22.h"
+
+#include "dht22.pio.h"
+#include "hardware/clocks.h"
+#include "hardware/gpio.h"
+#include "pico/stdlib.h"
+
+#define DHT22_START_LOW_US    1200u
+#define DHT22_PREPARE_US      30u
+#define DHT22_WORD_TIMEOUT_US 2000u
+
+static bool wait_for_rx_word(PIO pio, uint sm, uint32_t *out, uint32_t timeout_us) {
+    uint64_t deadline = time_us_64() + timeout_us;
+    while (pio_sm_is_rx_fifo_empty(pio, sm)) {
+        if (time_us_64() > deadline) {
+            return false;
+        }
+    }
+    *out = pio_sm_get(pio, sm);
+    return true;
+}
+
+void dht22_init(dht22_t *dev, PIO pio, uint sm, uint pin) {
+    dev->pio = pio;
+    dev->sm = sm;
+    dev->pin = pin;
+    dev->offset = pio_add_program(pio, &dht22_program);
+
+    pio_gpio_init(pio, pin);
+
+    pio_sm_config c = dht22_program_get_default_config(dev->offset);
+    sm_config_set_in_pins(&c, pin);
+    sm_config_set_clkdiv(&c, (float)clock_get_hz(clk_sys) / 1000000.0f);
+    sm_config_set_in_shift(&c, false, true, 8);
+
+    pio_sm_init(pio, sm, dev->offset, &c);
+    pio_sm_set_enabled(pio, sm, false);
+
+    gpio_init(pin);
+    gpio_pull_up(pin);
+    gpio_set_dir(pin, GPIO_IN);
+}
+
+dht22_status_t dht22_read(dht22_t *dev, int16_t *temperature_x10, uint16_t *humidity_x10) {
+    if (!gpio_get(dev->pin)) {
+        return DHT22_BUS_STUCK;
+    }
+
+    gpio_set_dir(dev->pin, GPIO_OUT);
+    gpio_put(dev->pin, 0);
+    sleep_us(DHT22_START_LOW_US);
+
+    gpio_set_dir(dev->pin, GPIO_IN);
+    gpio_pull_up(dev->pin);
+    sleep_us(DHT22_PREPARE_US);
+
+    pio_sm_set_enabled(dev->pio, dev->sm, false);
+    pio_sm_clear_fifos(dev->pio, dev->sm);
+    pio_sm_restart(dev->pio, dev->sm);
+    pio_sm_set_enabled(dev->pio, dev->sm, true);
+
+    uint8_t data[5] = {0};
+    for (uint i = 0; i < 5; ++i) {
+        uint32_t word = 0;
+        if (!wait_for_rx_word(dev->pio, dev->sm, &word, DHT22_WORD_TIMEOUT_US)) {
+            pio_sm_set_enabled(dev->pio, dev->sm, false);
+            return DHT22_TIMEOUT;
+        }
+        data[i] = (uint8_t)word;
+    }
+
+    pio_sm_set_enabled(dev->pio, dev->sm, false);
+
+    uint8_t checksum = (uint8_t)(data[0] + data[1] + data[2] + data[3]);
+    if (checksum != data[4]) {
+        return DHT22_CHECKSUM_ERROR;
+    }
+
+    uint16_t raw_h = (uint16_t)((data[0] << 8) | data[1]);
+    uint16_t raw_t = (uint16_t)((data[2] << 8) | data[3]);
+
+    *humidity_x10 = raw_h;
+    if (raw_t & 0x8000u) {
+        *temperature_x10 = -(int16_t)(raw_t & 0x7fffu);
+    } else {
+        *temperature_x10 = (int16_t)raw_t;
+    }
+
+    return DHT22_OK;
+}