From 089d8a62f16c6f29ae01803f6ac5729e7fe8f1ce Mon Sep 17 00:00:00 2001
From: Arthur Roberts <arfa.r@live.com>
Date: Mon, 30 Oct 2023 21:38:35 +0000
Subject: [PATCH] I get a timing error on every 4th bit

No idea why
---
 components/dht22/dht22.c | 87 +++++++++++++++++++++++++---------------
 main/main.c              |  2 +-
 2 files changed, 56 insertions(+), 33 deletions(-)

diff --git a/components/dht22/dht22.c b/components/dht22/dht22.c
index 90d994f..6ea1130 100644
--- a/components/dht22/dht22.c
+++ b/components/dht22/dht22.c
@@ -27,9 +27,28 @@ void dht22_handle_error(dht22_error e) {
   }
 }
 
+uint32_t wait_for_signal_to_change_from(int signal_level) {
+  uint32_t tick_total = 0;
+  uint64_t start_time = esp_timer_get_time();
+
+  while (gpio_get_level(CONFIG_DHT22_DATA_GPIO) == signal_level) {
+    tick_total += 1;
+    // TODO: Find a better way to determine the max timeout - perhaps find number of ticks
+    //   in 50ms or something
+    //   Or perhaps do actually run esp_timer_get_time in the loop or something
+    if (tick_total == (UINT32_MAX - 1)) {
+      return DHT22_TIMING_ERROR;
+    }
+  }
+
+  uint64_t next_time = esp_timer_get_time();
+  uint32_t elapsed_time = next_time - start_time;
+  return elapsed_time;
+}
+
 dht22_error dht22_read() {
   uint8_t data[5] = {0};
-  uint32_t tick_total = 0;
+  uint32_t elapsed_time;
 
   /*
    * From datasheet:
@@ -56,43 +75,47 @@ dht22_error dht22_read() {
     // wait for a while - should only be 20 uS
   }
 
-
-  uint64_t start_time = esp_timer_get_time();
-
-  while (gpio_get_level(CONFIG_DHT22_DATA_GPIO) == 0) {
-    tick_total += 1;
-    if (tick_total == UINT32_MAX - 1) {
-      return DHT22_TIMING_ERROR;
-    }
-  }
-  uint64_t next_time = esp_timer_get_time();
-  uint32_t elapsed_time = next_time - start_time;
-  if (elapsed_time < 75 || elapsed_time > 85) {
-    return DHT22_TIMING_ERROR;
-  }
-
-  tick_total = 0;
-  start_time = esp_timer_get_time();
-  while (gpio_get_level(CONFIG_DHT22_DATA_GPIO) == 0) {
-    tick_total += 1;
-    if (tick_total == UINT32_MAX - 1) {
-      return DHT22_TIMING_ERROR;
-    }
-  }
-  next_time = esp_timer_get_time();
-  elapsed_time = next_time - start_time;
-
-  portENABLE_INTERRUPTS();
-  ESP_LOGW(TAG, "etime: %lu", elapsed_time);
-
+  elapsed_time = wait_for_signal_to_change_from(0);
   if (elapsed_time < 70 || elapsed_time > 90) {
     return DHT22_TIMING_ERROR;
   }
 
+  elapsed_time = wait_for_signal_to_change_from(1);
+  if (elapsed_time < 70 || elapsed_time > 90) {
+    return DHT22_TIMING_ERROR;
+  }
+
+  /*
+   * From datasheet:
+   *  - DHT pulls low 50us -> into to next bit
+   *  - DHT pulls high:
+   *     - if 26-28us -> 0 bit
+   *     - if 70us -> 1 bit
+   */
+  portENABLE_INTERRUPTS();
+  for (int byte_i = 4; byte_i >= 0; byte_i--) {
+    for (int bit_i = 0; bit_i <= 8; bit_i++) {
+
+      elapsed_time = wait_for_signal_to_change_from(0);
+      if (elapsed_time < 35 || elapsed_time > 65) {
+        return DHT22_TIMING_ERROR;
+      }
+
+      elapsed_time = wait_for_signal_to_change_from(1);
+      /*
+      if (elapsed_time < 60 || elapsed_time > 80) {
+        data[byte_i] |= (1 << bit_i);
+      }
+      */
+      ESP_LOGE(TAG, "elapsed_time: %lu", elapsed_time);
+    }
+
+  }
+
   // TODO test that data[x] << 8 will be promoted to 16bits otherwise I'm
   // shifting them to just zeros
-  _dht22_relative_humidity = data[0] << 8 | data[1];
-  _dht22_temperature = (data[2] & 0x7f) << 8 | data[3];
+  _dht22_relative_humidity = (data[0] << 8) | data[1];
+  _dht22_temperature = ((data[2] & 0x7f) << 8) | data[3];
   if (data[2] & 0x80) {
     _dht22_temperature = -1 * _dht22_temperature;
   }
diff --git a/main/main.c b/main/main.c
index d1a7681..b233b7e 100644
--- a/main/main.c
+++ b/main/main.c
@@ -70,12 +70,12 @@ void read_from_dht22() {
     portDISABLE_INTERRUPTS();
     int ret = dht22_read();
     portENABLE_INTERRUPTS();
-    ESP_LOGE(TAG, "dht_ret: %i", ret);
     if (ret != DHT22_OK) {
       dht22_handle_error(ret);
     } else {
       latest_datapoint.temp = dht22_temperature();
       latest_datapoint.rh = dht22_relative_humidity();
+      ESP_LOGW(TAG, "%f & %f", latest_datapoint.temp / 10.0, latest_datapoint.rh / 10.0 );
 
       if (has_ntp_time_obtained_once()) {
         // I _think_ I only want to be doing that rolling average and saving