Started some DHT22 stuff

Haven't tested it at all

components/dht22/dht22.c

@@ -7,10 +7,36 @@
 #error "Please define your DHT22 GPIO Data Pin"
 #endif /* CONFIG_DHT22_DATA_GPIO == -1 */
 
-dht22_error dht_read() {
-  return DHT_OK;
+static const char* TAG = "DHT22";
+deci_percent   _dht22_relative_humidity = UINT16_MAX;
+deci_degrees_c _dht22_temperature = INT16_MIN;
+
+
+dht22_error dht22_read() {
+  uint8_t data[5] = {0};
+
+
+  // TODO: Actually figure out how to read the data from the chip.
+  
+  // 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];
+  if (data[2] & 0x80) {
+      _dht22_temperature = -1 * _dht22_temperature;
+  }
+  uint8_t checksum_val = (data[0] + data[1] + data[2] + data[2]) & 0xff;
+  if (checksum_val != data[5]) {
+    _dht22_relative_humidity = UINT16_MAX;
+    _dht22_temperature = INT16_MIN;
+    return DHT22_CHECKSUM_ERROR;
+  }
+  
+  return DHT22_OK;
 }
 
-int dht_temperature() {
-  return DATA_GPIO;
+deci_percent dht22_relative_humidity() {
+  return _dht22_relative_humidity;
+}
+deci_degrees_c dht22_temperature() {
+  return _dht22_temperature;
 }

components/dht22/dht22.h

@@ -1,10 +1,18 @@
 #pragma once
 
+#include <stdint.h>
+
 typedef enum {
-  DHT_OK
+  DHT22_OK,
+  DHT22_TIMING_ERROR,
+  DHT22_CHECKSUM_ERROR,
 } dht22_error;
 
-int dht_temperature();
-dht22_error dht_read();
+typedef uint16_t deci_percent;
+typedef int16_t  deci_degrees_c;
+
+deci_percent dht22_relative_humidity();
+deci_degrees_c dht22_temperature();
+dht22_error dht22_read();