How do I use DHT11 sensor on TM4C123GH6PM?

Perhaps your method of, "Diving directly into an application" but without the normal/customary "build-up" of required experience & MCU skills - proves an issue?

Looking downstream - once you've successfully "transacted" with your remote device - what then?    Surely you'll want to display the sensor's results.    Maybe even, "take some actions" based upon those results.    What then?

These MCUs are complex - usually new users have to "really commit" - expend serious time/effort to gain "reasonable" competence.

Starting with an application - too often - "short circuits" the normal learning process - leading to posts nearly identical to yours.

This vendor has produced extensive "learning aids" - manuals, videos, rich & extensive code examples - even this forum.  

I'd bet that a better (i.e. some) search of this forum may reveal code to your objective.    But I don't recommend that - "Frankenstein" may have (from a distance) looked human - but up close - not so much.     And that's exactly "true" for "quick/dirty" code finds - if you don't properly understand - you'll soon ship-wreck - wash ashore - that's a promise...    And (then) what?    Real learning - understanding - is your answer...

Doesn't matter through what you send the signal... You just need to follow those timings.
I used a similar interface IC with either the PWM module, the SPI module or the GPIO. You have to chose the best option

Robert Adsett72 said:

What they are saying is that you need to drive the line low and let it float high to let the ic respond.  

This reporter is far from the accomplished translating/interpreting skills of o.p. and friend Robert.

Yet - can, "Let it float high" be correct?    Firm's instruction, "then MCU will pull up" indicates not so much a "float" as a pull-up - so that a known signal level is established.

I've not read this device's data - this sounds like some variant of, "One wire bus" where the single communication line proves bi-directional.    Thus - poster's use of UART - which neither enables fine tuning (& quick alteration of bit timing) & which is unable to quickly/easily switch from output to input - appears very flawed...

Forum cannot - and should not - serve the "bottom of the barrel - sensor du jour" - "This x@#$! sensor don't work!" - endless series of requests...  

Luis Afonso said:

to let it float you should switch the pin to input

Should you (really) let an input, "float?"    Of course you know that's not correct/proper - and as you've said (often) here - GPIO inputs should always be graced with a suitable logic level.  (which never is "float")

Luis - very, very difficult to, "defend the indefensible!"

Look again at your newest writing, "it (data line) will be pulled high by the pull-up when left floating."    While that's technically possible (to pull up a pin switched to an input - after that "switch to input" has occurred) such "signal level sequencing" proves, "in the noise."    Most always - pull up is present/accounted for - thus the GPIO - even when switched to input - is "never" floating!   (it may float if the pull up does not directly attach to 3V3 - but instead to a GPIO output - or other controlled voltage source - but this is outside, "normal/customary" as it "eats" MCU resources)

Simply put - the bi-di data pin - in focus here - is "never" floating...

Below is driver for DHT11 and DHT22 (just enable #define in header). To use on main() first call dht_init() and then call dht_readTH(&th); where th is a struct defined in driver header.

this is the driver header:

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_timer.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/timer.h"


#ifndef __DHT22_H
#define __DHT11_H

// default is DHT22 = RHT03
#define DHT11_DISABLED

#define DHT_PORT_PERIPH SYSCTL_PERIPH_GPIOF
#define DHT_PORT GPIO_PORTF_BASE
#define DHT_PIN GPIO_PIN_4

#define DHT_TIM_PERIPH	SYSCTL_PERIPH_TIMER5
#define DHT_TIM_BASE	TIMER5_BASE
#define DHT_TIM			TIMER_A

#define MCU_CLOCK SysCtlClockGet()
#define DHT_WAIT_18ms ((MCU_CLOCK*18)/3000)
#define DHT_WAIT_20us ((MCU_CLOCK*2)/300000)

#define DHT_TIMEOUT ((MCU_CLOCK*9)/100000) // 90us
#define DHT_TIME_BIT_1 ((MCU_CLOCK*7)/100000) // 70us

#define DON()		GPIOPinTypeGPIOOutput(DHT_PORT, DHT_PIN)
#define DIN()		GPIOPinTypeGPIOInput(DHT_PORT, DHT_PIN)

#define DHT_DATA(__DATA__)	GPIOPinWrite(DHT_PORT, DHT_PIN, (__DATA__))
#define DHT_READ	GPIOPinRead(DHT_PORT, DHT_PIN)


typedef struct {
    float celsius_temp;
    float humidity;
} DHT_TypeDef;


// Interface
void dht_init(void);
uint8_t dht_readTH(DHT_TypeDef *);



#endif

and this is the actual driver

#include "ms_dht11.h"


// Private methods
static float dht_readTemperature(void);
static float dht_readHumidity(void);
static uint8_t dht_read(void);
static void DHTIntHandler(void);


// Private data
uint8_t data_buffer[6];
uint32_t dht_timing;
bool quit_timing = false;



void dht_init() {

	SysCtlPeripheralEnable(DHT_PORT_PERIPH);
	SysCtlPeripheralEnable(DHT_TIM_PERIPH);

    TimerConfigure(DHT_TIM_BASE, TIMER_CFG_ONE_SHOT_UP);
    TimerLoadSet(DHT_TIM_BASE, DHT_TIM, DHT_TIMEOUT+1000);

    // set interrupt for counter
    GPIOIntEnable(DHT_PORT, DHT_PIN);
	GPIOIntTypeSet(DHT_PORT, DHT_PIN, GPIO_BOTH_EDGES); // config interrupt both edges
	GPIOIntRegister(DHT_PORT, DHTIntHandler);

	DON();
    DHT_DATA(DHT_PIN);

}


// RETURN:
// 1 = success reading from sensor;
// 0 = error on reading from sensor;
// also return T and H

uint8_t dht_readTH(DHT_TypeDef *values) {

    if (dht_read() == 1) {
        // temperature
        values->celsius_temp = dht_readTemperature();

        // humidity
        values->humidity = dht_readHumidity();

        return 1;
    }

    return 0;
}


float dht_readTemperature() {

    float t;

#ifdef DHT11
    t = data_buffer[2];
#else

    t = data_buffer[2] & 0x7F;
    t *= 256;
    t += data_buffer[3];
    t /= 10.0;

    if (data_buffer[2] & 0x80)
        t *= -1.0;

    if (t > 80.0) {
    	t = 80.0;
    }
    if (t < -40.0) {
    	t = -40.0;
    }


#endif

    return t;
}


float dht_readHumidity() {

    float h;

#ifdef DHT11
    h = data_buffer[0];
#else
    h = data_buffer[0];
    h *= 256;
    h += data_buffer[1];
    h /= 10.0;

    if (h > 100.0) {
    	h = 100.0;
    }
    if (h < 0.0) {
    	h = 0.0;
    }

#endif

    return h;
}



uint8_t dht_read(void) {
    uint8_t ii, byteIdx, bitCounter;


    // clear data
    for (ii=0; ii< 5; ii++)
        *(data_buffer + ii) = 0;


    // send start signal low and wait 1-18 ms
    DON();
    DHT_DATA(0x00);
    SysCtlDelay(DHT_WAIT_18ms);

    // send pull up signal high and wait 20-40 us
    DHT_DATA(DHT_PIN);
    // wait at least 20us
    SysCtlDelay(DHT_WAIT_20us);
    DIN();
    while(GPIOPinRead(DHT_PORT, DHT_PIN) == DHT_PIN);

    // acknowledge ~80us low
    while(GPIOPinRead(DHT_PORT, DHT_PIN) == 0x00);
    // acknowledge ~80us high
    while(GPIOPinRead(DHT_PORT, DHT_PIN) == DHT_PIN);

    // gets data 5 bytes, 40 bits
    // every bit start with low level for 50us then high level last
    // 0 = 26-28us
    // 1 = 70us
    byteIdx = 0;
    bitCounter = 7;
    for (ii=0; ii<40; ii++) {
    	quit_timing = false;
    	//SysCtlDelay(DHT_WAIT_50us);

        // do elaboration
    	while(!quit_timing) {
    		if (dht_timing > DHT_TIMEOUT) {
    			UARTprintf("timeout\r\n");
    			return 0;
    		}

    	}

        // check bit (timing is 1us) 26-28 -> 0 - 70us -> 1
        if (dht_timing > DHT_TIME_BIT_1) {
            data_buffer[byteIdx] |= (1 << bitCounter);
        }

        if (bitCounter == 0) {
            bitCounter = 7;
            byteIdx++;
        } else
            bitCounter--;

    }

    // check we read 40 bits and that the checksum matches
    if ((byteIdx == 5) && (data_buffer[4] == ( (data_buffer[0] + data_buffer[1] + data_buffer[2] + data_buffer[3]) & 0xFF) ) ) {
        return 1;
    }


    return 0;

}


void DHTIntHandler()
{

	volatile int32_t start_timer;


	GPIOIntClear(DHT_PORT, DHT_PIN); // clear interrupt flag
	if (GPIOPinRead(DHT_PORT, DHT_PIN) == DHT_PIN) { // check low to high
		TimerEnable(DHT_TIM_BASE, DHT_TIM);
		start_timer = TimerValueGet(DHT_TIM_BASE, DHT_TIM);
		quit_timing = false;
	} else { // check high to low, finish
	    TimerDisable(DHT_TIM_BASE, DHT_TIM);
	    dht_timing = TimerValueGet(DHT_TIM_BASE, DHT_TIM);
	    dht_timing -= start_timer;
    	quit_timing = true;
    	HWREG(DHT_TIM_BASE + TIMER_O_TAV) = 0;
	}

}

Hope this helps

First of all I assume you have included the header file in your main file. Then, if program does not compiles, CCS gives you an error. Can you please post the compiler error?

For me the driver works well. For your error please see this link  or this threads  Basically the issue had something to do with the version of the ARM compiler. Do you have compiled other projects ?

Hi Amit,

Thanks for your reply!

DHT_PORT is defined as GPIO_PORTB_BASE         0x40005000  // GPIO Port B and the value is the same 0x40005000.

do have any idea for change this value?

BR

Hermes

DHT_PORT is defined as GPIO_PORTF_BASE. 

Ok, attached is a complete CCS project for DHT11. If you use DHT22 read ms_dht11.h comments.

Hope this helps

MicheleDHT.zip

Thks Michele for you reply.

I´ll to try it.

Hermes

Hello Michele.

I built the original project that you sent without errors. But, when I debugged in my board, the Temperature (T) and Humidity (H) always returned 0.

I realized that the dht_readTH() always return zero, so, the variable didn´t return the T and H values. I tried to follow the code and see where does it crash, but, I couldn´t recognize the error. I printed it and attached here to you in a zip file (3 photos). 

Did you have these problem too?

Thank you Michele.

Hermes

dht_readTH() returning problem.rar

Hi Hermes,

first check in ms_dht11.h this lines:

// default is DHT11, comment this define for DHT22 = RHT03
#define DHT11

Then, are you sure your module is 3.3V compatible? I hope so.

After that I suspect there are timing issues. I've used a DHT11 with a 1K resistor (I do not use a module like the ones I see in the photos you sent me). So I suggest tweaking with thiis values

#define DHT_TIMEOUT ((MCU_CLOCK*9)/100000) // 90us

#define DHT_TIME_BIT_1 ((MCU_CLOCK*7)/100000) // 70us

and myabe with 

#define DHT_WAIT_18ms ((MCU_CLOCK*18)/3000)
#define DHT_WAIT_20us ((MCU_CLOCK*2)/300000)

If you have a logic analyzer things are more simple.

Otherwise you can sent me the schematics of your module and I'll try to figure out what's the problem.

Regards

Michele

Hello,

It was some time ago, but if I remember correctly, you should adjust timers to be in sync with the sensor. Take a look at the DHT11 datasheet and set interrupts to the intervals specified there, if it doesn't work (you may get wrong readings, like I did), try changing these intervals to a little longer or a little smaller till you get the correct values. Pay attention when converting the sensors data, since it is a bit strange.

I would share the code, but I really have no ideia where are the files...