CCS/TM4C123GH6PM: DHT22 Temp and Humidity sensor: Read values = 0.0 C and 0.0%

Hi Charles :)

I have some good news! I tried and modified a new code I found @ https://www.instructables.com/Weather-Monitoring-System-Using-TIVA/

Finally, I have some non-zero readings from the sensor. The humidity value seems accurate but the temperature value is off. I suppose I need to review the binary to decimal conversion in the code. But that is something I can figure out comfortably.

Thank you very much for your help. Maybe when I have the code working accurately, I will share it here.

Regards

Swapna

Hello,

Here is the code that works for interfacing the DHT22 sensor to the Tiva C Series. My connections were 

Pin1 --> 3.3V

Pin2--> PC4

Pin3-->

Pin4--> GND

#include <stdint.h>
#include <stdio.h>
#include <stdbool.h>
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "utils/uartstdio.h"
#include "drivers/ms_dht11.h"

// Constants for Temperature and Humidity Sensor
#define Clock_GPIO_C 0x04
#define DIR_PIN4_In ~0x10
#define DIR_PIN4_Out 0x10
#define High_In 0x10
#define Low_In ~0x10
#define High_Out 0x10
#define Low_Out 0x00
#define DEN_ENABLE_C4 0x10

void ConfigureUART(void);

//-----for the display output on Putty-------//
void ConfigureUART(void)
{

SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

GPIOPinConfigure(GPIO_PA0_U0RX);
GPIOPinConfigure(GPIO_PA1_U0TX);
GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);

UARTStdioConfig(0, 115200, SysCtlClockGet());

}

int Binary2Decimal(int Bit_L, int Bit_H, unsigned int Binary[])
{
int temp=0,i;
for(i = Bit_L;i<Bit_H;i++)
temp += Binary[i] * (1<<((Bit_H-1)-i)); //1 << n is the same as raising 2 to the power n, or 2^n
return temp;
}

/* This function generates the delay. */

void Delay(unsigned long int period)
{
int i=0;
for(i=0;i<12*(period/10);i++);
}

int main(void)

{
//---------------- Variables for Humidity and Temperature Sensor----------------------------------//

ConfigureUART(); //Enabling UART display (putty)
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3);

UARTprintf("Let's get started (Freq=%d)!\r\n", SysCtlClockGet());

int i=0;
unsigned int Data[40];
int Temp_16, Temp_High, Temp_Low; // Varaibles for Temperature
int RH_16, RH_High, RH_Low; // Variables for Relative Humidity
int Check_Sum, temp, temp1, temp2, sum; // Variables for Parity Checking

SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
// RCGC_GPIO_R |= Clock_GPIO_C; // Clock for Port C
Delay(100); // Delay to make Clock Smooth
//GPIO_PORTC_DEN_R |= DEN_ENABLE_C4; // Set Pin C4 as Digital

//------------------Collecting the data from the sensor------------------------------------------//
while(1)
{
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1, 0x02);// For taking and displaying values of Sensors again and gain (infinitely)
while(1) // Iterates untill temperature and humidity values are true
{
GPIOPinTypeGPIOOutput(GPIO_PORTC_BASE, GPIO_PIN_4); // Set Pin C4 as output
GPIOPinWrite(GPIO_PORTC_BASE,GPIO_PIN_4,Low_In);
//GPIO_PORTC_DATA_R &= Low_In; // Set data line low for 1ms to awake the sensor
Delay(1000);
GPIOPinWrite(GPIO_PORTC_BASE,GPIO_PIN_4,High_In);
//GPIO_PORTC_DATA_R |= High_In; // Set data line high for 30us
Delay(30);
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1, 0x00);
GPIOPinTypeGPIOInput(GPIO_PORTC_BASE, GPIO_PIN_4); // Set Pin C4 as Input
while ((GPIOPinRead(GPIO_PORTC_BASE, GPIO_PIN_4)) == Low_Out) // Iterates untill data line is low
{}
while(GPIOPinRead(GPIO_PORTC_BASE, GPIO_PIN_4) == High_Out) // Iterates untill data line is high
{}
while(i<40)
{ // Iterates to get 40 bits data from the sensor
while(GPIOPinRead(GPIO_PORTC_BASE, GPIO_PIN_4) == Low_Out) // Iterates untill the data line is low
{}
Delay(45);
if(GPIOPinRead(GPIO_PORTC_BASE, GPIO_PIN_4) == Low_Out) // Check after 45us
Data[i] = 0; // if data line is low // 0 bit by sensor
else // else
Data[i] = 1; // 1 bit by sensor
while(GPIOPinRead(GPIO_PORTC_BASE, GPIO_PIN_4) == High_Out) // Iterates till the data line is high
{}
i++;
}
//------------------Processing the data from the sensor------------------------------------------//
i=0;
RH_High = Binary2Decimal(0,8,Data); // Converts first 8 bits (Humidity bits) of the data into Decimal value
RH_Low = Binary2Decimal(8,16,Data); // Converts 8-16 bits of (Humidity bits) the data into Decimal value
Temp_High = Binary2Decimal(17,24,Data); // Converts 17-24 bits of (Temperature bits) the data into Decimal value
Temp_Low = Binary2Decimal(24,32,Data); // Converts 24-32 bits of (Temperature bits) the data into Decimal value
Check_Sum = Binary2Decimal(32,40,Data); // Converts last 8 bits of (Parity bits) the data into Decimal value
sum = RH_High + RH_Low + Temp_High + Temp_Low; // Sum the 8 high and 8 low bits of both humidity and temperature
if(sum>255)
sum -= 256; // To keep the sum 8 bit long
if(Check_Sum == sum) // Parity checking
break; // if no error, breaks the above while loop
}
RH_16 = Binary2Decimal(0,16,Data); // Converts Humidity bits into Decimal value
temp1 = RH_16/10;
Temp_16 = Binary2Decimal(17,32,Data); // Converts Temperature bits into Decimal value
temp2 = Temp_16/10;

//------------------Displaying the data from the sensor through UART and PuTTY------------------------------------------//

UARTprintf(" H=%d.%d T=%d.%d \r\n", temp1,RH_16%10, temp2,Temp_16%10);
// UARTprintf(" H=%d T=%d\r\n", temp1/10+48,temp2/10+48 );
// Wait for two seconds
Delay(2000000);
}
}