From e139aa7e9c3bde453c0de29e0338e464028b791f Mon Sep 17 00:00:00 2001
From: Arthur Roberts <arfa.r@live.com>
Date: Mon, 30 Oct 2023 22:11:39 +0000
Subject: [PATCH] Every 4th byte comes back with zero time elapsed high.

Really don't know why
---
 components/dht22/dht22.c | 27 +++++++++++++++------------
 components/dht22/dht22.h |  2 ++
 main/main.c              |  1 +
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/components/dht22/dht22.c b/components/dht22/dht22.c
index 6ea1130..2130de5 100644
--- a/components/dht22/dht22.c
+++ b/components/dht22/dht22.c
@@ -24,25 +24,28 @@ void dht22_handle_error(dht22_error e) {
     ESP_LOGE(TAG, "Error calculating checksum");
   } else if (e == DHT22_TIMING_ERROR) {
     ESP_LOGE(TAG, "Timing error while obtaining data");
+  } else if (e == DHT22_TIMEOUT_ERROR) {
+    ESP_LOGE(TAG, "Timeout error - waited >2ms for signal to change");
+  } else {
+    ESP_LOGE(TAG, "Unknown error: %i", 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();
+  uint64_t next_time = start_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;
+    next_time = esp_timer_get_time();
+    if ((next_time - start_time) >= 1000 * 10) {
+      return DHT22_TIMEOUT_ERROR;
     }
   }
 
-  uint64_t next_time = esp_timer_get_time();
   uint32_t elapsed_time = next_time - start_time;
+  if (elapsed_time == 0) {
+    return 1000;
+  }
   return elapsed_time;
 }
 
@@ -97,19 +100,19 @@ dht22_error dht22_read() {
     for (int bit_i = 0; bit_i <= 8; bit_i++) {
 
       elapsed_time = wait_for_signal_to_change_from(0);
+      if (elapsed_time == DHT22_TIMEOUT_ERROR) {
+        return DHT22_TIMEOUT_ERROR;
+      }
       if (elapsed_time < 35 || elapsed_time > 65) {
-        return DHT22_TIMING_ERROR;
+        return elapsed_time;
       }
 
       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
diff --git a/components/dht22/dht22.h b/components/dht22/dht22.h
index cf488f3..cf479fc 100644
--- a/components/dht22/dht22.h
+++ b/components/dht22/dht22.h
@@ -1,9 +1,11 @@
 #pragma once
 
+#include <limits.h>
 #include <stdint.h>
 
 typedef enum {
   DHT22_OK,
+  DHT22_TIMEOUT_ERROR,
   DHT22_TIMING_ERROR,
   DHT22_CHECKSUM_ERROR,
 } dht22_error;
diff --git a/main/main.c b/main/main.c
index b233b7e..4078799 100644
--- a/main/main.c
+++ b/main/main.c
@@ -73,6 +73,7 @@ void read_from_dht22() {
     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 );