Added DHT and improved OneWire

lib/adc.c

@@ -23,7 +23,7 @@ void adc_disable()
 /** Sample analog pin with 8-bit precision */
 uint8_t adc_read_byte(uint8_t channel)
 {
-	write_low_nibble(ADMUX, channel);  // Select channel to sample
+	set_low_nibble(ADMUX, channel);  // Select channel to sample
 	sbi(ADMUX, ADLAR);  // Align result to left
 	sbi(ADCSRA, ADSC);  // Start conversion
 
@@ -36,7 +36,7 @@ uint8_t adc_read_byte(uint8_t channel)
 /** Sample analog pin with 10-bit precision */
 uint16_t adc_read_word(uint8_t channel)
 {
-	write_low_nibble(ADMUX, channel);  // Select channel to sample
+	set_low_nibble(ADMUX, channel);  // Select channel to sample
 	cbi(ADMUX, ADLAR);  // Align result to right
 	sbi(ADCSRA, ADSC);  // Start conversion
 

lib/dht11.c

@@ -0,0 +1,88 @@
+#include <avr/io.h>
+#include <util/delay.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "iopins.h"
+#include "dht11.h"
+
+/** Read one bit */
+bool _dht11_rxbit(const uint8_t pin)
+{
+	// Wait until start of pulse
+	while (is_low_n(pin));
+
+	uint8_t cnt = 0;
+	while (is_high_n(pin))
+	{
+		cnt++;
+		_delay_us(5);
+	}
+
+	return (cnt > 8);
+}
+
+
+/** Read one byte */
+uint8_t _dht11_rxbyte(const uint8_t pin)
+{
+	uint8_t byte = 0;
+
+	for (uint8_t i = 0; i < 8; i++)
+	{
+		if (_dht11_rxbit(pin))
+			byte |= (1 << (7 - i));
+	}
+
+	return byte;
+}
+
+
+/** Read tehmperature and humidity from the DHT11, returns false on failure */
+bool dht11_read(const uint8_t pin, dht11_result_t* result)
+{
+	// bus down for > 18 ms
+	as_output_n(pin);
+	pin_low_n(pin);
+	_delay_ms(20);
+
+	// bus up for 20-40us
+	pin_high_n(pin);
+	_delay_us(20);
+
+	// release
+	as_input_pu_n(pin);
+
+	// DHT should send 80us LOW & 80us HIGH
+
+	_delay_us(40);
+	if (!is_low_n(pin))
+		return false; // init error
+
+	_delay_us(80);
+	if (!is_high_n(pin))
+		return false; // init error
+
+	// skip to start of first bit
+	_delay_us(50);
+
+	// Receive 5 data bytes (Rh int, Rh dec, Temp int, Temp dec, Checksum)
+	// Decimal bytes are zero for DHT11 -> we can ignore them.
+	uint8_t bytes[5];
+	uint8_t sum = 0;
+
+	for (uint8_t i = 0; i < 5; i++)
+	{
+		uint8_t b = _dht11_rxbyte(pin);
+		bytes[i] = b;
+		if (i < 4) sum += b;
+	}
+
+	// Verify checksum
+	if (sum != bytes[4]) return false;
+
+	result->rh = bytes[0];
+	result->temp = bytes[2];
+
+	return true;
+}

lib/dht11.h

@@ -0,0 +1,16 @@
+#pragma once
+
+//
+// Reading temperature and relative humidity from DHT11
+//
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct {
+	int8_t temp;
+	int8_t rh;
+} dht11_result_t;
+
+/** Read tehmperature and humidity from the DHT11, returns false on failure */
+bool dht11_read(const uint8_t pin, dht11_result_t* result);

lib/onewire.c

@@ -26,7 +26,7 @@ bool ow_reset(const uint8_t pin)
 
 
 /** Send a single bit */
-void ow_tx_bit(const uint8_t pin, const bool bit)
+void _ow_tx_bit(const uint8_t pin, const bool bit)
 {
 	as_output_n(pin);
 	pin_low_n(pin);
@@ -48,13 +48,13 @@ void ow_send(const uint8_t pin, const uint8_t byte)
 {
 	for (uint8_t i = 0; i < 8; i++)
 	{
-		ow_tx_bit(pin, (byte >> i) & 0x01);
+		_ow_tx_bit(pin, (byte >> i) & 0x01);
 	}
 }
 
 
 /** Read a single bit */
-bool ow_rx_bit(const uint8_t pin)
+bool _ow_rx_bit(const uint8_t pin)
 {
 	as_output_n(pin);
 	pin_low_n(pin);
@@ -78,7 +78,7 @@ uint8_t ow_read(const uint8_t pin)
 
 	for (uint8_t i = 0; i < 8; i++)
 	{
-		byte = (byte >> 1) | (ow_rx_bit(pin) << 7);
+		byte = (byte >> 1) | (_ow_rx_bit(pin) << 7);
 	}
 
 	return byte;
@@ -186,6 +186,7 @@ uint8_t crc8(uint8_t *addr, uint8_t len)
 
 // --- utils for DS1820 ---
 
+
 /** Read temperature in 0.0625°C, or TEMP_ERROR on error */
 int16_t ds1820_read_temp(uint8_t pin)
 {
@@ -222,3 +223,19 @@ int16_t ds1820_read_temp_c(uint8_t pin)
 	return (int16_t) temp;
 }
 
+
+bool ds1820_single_measure(uint8_t pin)
+{
+	ow_reset(pin);
+	ow_send(pin, SKIP_ROM);
+	ow_send(pin, CONVERT_T);
+
+	if(!ow_wait_ready(pin)) {
+		return false;
+	}
+
+	ow_reset(pin);
+	ow_send(pin, SKIP_ROM);
+
+	return true;
+}

lib/onewire.h

@@ -1,5 +1,9 @@
 #pragma once
 
+//
+// Utils for Dallas OneWire bus (DS1820 etc)
+//
+
 #include <stdint.h>
 #include <stdbool.h>
 
@@ -10,47 +14,45 @@
 /** Perform bus reset. Returns true if any device is connected */
 bool ow_reset(const uint8_t pin);
 
-
-/** Send a single bit */
-void ow_tx_bit(const uint8_t pin, const bool bit);
-
-
 /** Send a single byte */
 void ow_send(const uint8_t pin, const uint8_t byte);
 
-
-/** Read a single bit */
-bool ow_rx_bit(const uint8_t pin);
-
-
 /** Read a single byte */
 uint8_t ow_read(const uint8_t pin);
 
-
 /** Wait until the device is ready. Returns false on timeout */
 bool ow_wait_ready(const uint8_t pin);
 
-
 /** Read bytes into an array */
 void ow_read_arr(const uint8_t pin, uint8_t* array, const uint8_t count);
 
-
 /** Compute a CRC16 checksum */
 uint16_t crc16( uint8_t *data, uint8_t len);
 
-
 /** Compute a CRC8 checksum */
 uint8_t crc8(uint8_t *addr, uint8_t len);
 
-
 // --- utils for DS1820 ---
 
 #define TEMP_ERROR -32768
 
-/** Read temperature in 0.0625°C, or TEMP_ERROR on error */
+/**
+ * Read temperature in 0.0625°C, or TEMP_ERROR on error
+ * Use this where you'd normally use READ_SCRATCHPAD
+ */
 int16_t ds1820_read_temp(uint8_t pin);
 
 
-/** Read temperature in 0.1°C, or TEMP_ERROR on error */
+/**
+ * Read temperature in 0.1°C, or TEMP_ERROR on error
+ * Use this where you'd normally use READ_SCRATCHPAD
+ */
 int16_t ds1820_read_temp_c(uint8_t pin);
 
+/**
+ * Perform a temperature measurement with single DS1820 device on the line
+ * Can be followed by a call to read temperature (READ_SCRATCHPAD).
+ *
+ * Returns false on failure (device not connected)
+ */
+bool ds1820_single_measure(uint8_t pin);