Interfacing of SHT11 with PIC24f16KA102

hi,
i came to know from the SHT11 data sheet is ...

The sensor

cannot be addressed by I2C protocol; however, the sensor

can be connected to an I2C bus without interference with

other devices connected to the bus. The controller must

switch between the protocols.

i m getting error in the following code. I have taken this code from the one of the post of mikroelectronika (viewtopic.php?f=13&t=13803&start=15) and I have modified only the pins used for SDA and SCL and commented the code for LCD. But i m getting error when i interface PIC24F16KA102 with SHT11 click board. i m pasting my code here. plz help in debugging this problem. i am debugging the following code using MPLABX IDE, C16 compiler. i m getting error in main programme at the following point.



if(error!=0)
{
s_connectionreset(); //in case of an error: connection reset
}

/**************************************************************************************************
* Project name:
SHT11_driver
* Copyright:
(c) Mikroelektronika, 2011.
* Revision History:
20111122:
- initial release (DA and JK);
* Description:
This code contains functions for communication with SHT1x temperature and humidity sensor.
http://www.sensirion.com/en/pdf/product ... -SHT1x.pdf

* Test configuration:
SW: mikroC PRO for PIC
http://www.mikroe.com/eng/products/view ... o-for-pic/
**************************************************************************************************/

/*******************************************************************************************************************/
#include "p24F16KA102.h"
#include <timer.h>
#include <math.h>
typedef union
{ unsigned int i;
float f;
} value;


//------------------------------------------------------------------------------
// modul-var
//------------------------------------------------------------------------------
//enum {TEMP,HUMI};

//#include "initlcd.h"

#define TEMP 0
#define HUMI 1

#define PORT_COND TRISBbits.TRISB9 //data port condition: input/output
#define DATA PORTBbits.RB9 //SHT11 DATA pin
#define SCK PORTBbits.RB8 //STH11 SCK pin
#define noACK 0
#define ACK 1
//adr command r/w
#define STATUS_REG_W 0x06 //000 0011 0
#define STATUS_REG_R 0x07 //000 0011 1
#define MEASURE_TEMP 0x03 //000 0001 1
#define MEASURE_HUMI 0x05 //000 0010 1
#define RESET 0x1e //000 1111 0

#define MEMORY_ADDRESS 0xA0


// char* Out_temp()
// {
// char str[]="Temp:" absolute MEMORY_ADDRESS;
// return str;
// }
//
// char* Out_humi()
// {
// char str[]="Humi:" absolute MEMORY_ADDRESS;
// return str;
// }


//------------------------------------------------------------------------------
char s_write_byte(unsigned char value)
//------------------------------------------------------------------------------
// writes a byte on the Sensibus and checks the acknowledge
{
unsigned char i,error=0;

PORT_COND = 0; //SHT11 WRITE


for (i=0x80;i>0;i/=2) //shift bit for masking
{ if (i & value) DATA=1; //masking value with i , write to SENSI-BUS
else DATA=0;
SCK=1; //clk for SENSI-BUS
delay_us(5); //pulswith approx. 5 us
SCK=0;
}

DATA=1; //release DATA-line

PORT_COND = 1; //SHT11 READ


delay_us(2);

SCK=1; //clk #9 for ack
error=DATA; //check ack (DATA will be pulled down by SHT11)
SCK=0;
return error; //error=1 in case of no acknowledge
}


//----------------------------------------------------------------------------------
char s_read_byte(unsigned char ack)
//----------------------------------------------------------------------------------
// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1"
{
unsigned char i,val=0;

PORT_COND = 1; //SHT11 READ


DATA=1; //release DATA-line

for (i=0x80;i>0;i/=2) //shift bit for masking
{ SCK=1; //clk for SENSI-BUS

if (DATA) val=(val | i); //read bit
SCK=0;
}

DATA=!ack; //in case of "ack==1" pull down DATA-Line
SCK=1; //clk #9 for ack
delay_us(5); //pulswith approx. 5 us
SCK=0;
DATA=1; //release DATA-line
return val;
}


//----------------------------------------------------------------------------------
void s_transstart(void)
//----------------------------------------------------------------------------------
// generates a transmission start
// _____ ________
// DATA: |_______|
// ___ ___
// SCK : ___| |___| |______
{
PORT_COND = 0; //SHT11 WRITE

DATA=1; SCK=0; //Initial state
delay_us(2);
SCK=1;
delay_us(2);
DATA=0;
delay_us(2);
SCK=0;
delay_us(5);
SCK=1;
delay_us(2);
DATA=1;
delay_us(2);
SCK=0;
}


//----------------------------------------------------------------------------------
void s_connectionreset(void)
//----------------------------------------------------------------------------------
// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
// _____________________________________________________ ________
// DATA: |_______|
// _ _ _ _ _ _ _ _ _ ___ ___
// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |______
{
unsigned char i;

PORT_COND = 0; //SHT11 WRITE


DATA=1; SCK=0; //Initial state

for(i=0;i<9;i++) //9 SCK cycles
{ SCK=1;
SCK=0;
}

s_transstart(); //transmission start
}


//----------------------------------------------------------------------------------
char s_softreset(void)
//----------------------------------------------------------------------------------
// resets the sensor by a softreset
{
unsigned char error=0;

s_connectionreset(); //reset communication

error+=s_write_byte(RESET); //send RESET-command to sensor
return error; //error=1 in case of no response form the sensor
}


//----------------------------------------------------------------------------------
char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{
unsigned char error=0;

s_transstart(); //transmission start

error=s_write_byte(STATUS_REG_R); //send command to sensor

*p_value=s_read_byte(ACK); //read status register (8-bit)
*p_checksum=s_read_byte(noACK); //read checksum (8-bit)

return error; //error=1 in case of no response form the sensor
}


//----------------------------------------------------------------------------------
char s_write_statusreg(unsigned char *p_value)
//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
{
unsigned char error=0;

s_transstart(); //transmission start

error+=s_write_byte(STATUS_REG_W);//send command to sensor
error+=s_write_byte(*p_value); //send value of status register

return error; //error>=1 in case of no response form the sensor
}


//----------------------------------------------------------------------------------
char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char mode)
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
{
unsigned error=0;
unsigned int i;

s_transstart(); //transmission start

switch(mode)
{ //send command to sensor
case TEMP : error+=s_write_byte(MEASURE_TEMP); break; //temp
case HUMI : error+=s_write_byte(MEASURE_HUMI); break; //humidity
default : break;
}

PORT_COND = 1; //SHT11 READ


for (i=0;i<65535;i++) if(DATA==0) break; //wait until sensor has finished the measurement

if(DATA) error+=1; // or timeout (~2 sec.) is reached

*(p_value+1)=s_read_byte(ACK); //read the second byte (LSB)
*(p_value) =s_read_byte(ACK); //read the first byte (MSB)



*p_checksum =s_read_byte(noACK); //read checksum

return error;
}

/*
//----------------------------------------------------------------------------------
void init_uart()
//----------------------------------------------------------------------------------
// Initializes the UART so the final data can be sent away, e.g. to a PC
//9600 bps @ 11.059 MHz
{ SCON = 0x52;
TMOD = 0x20;
TCON = 0x69;
TH1 = 0xfd;
}
*/

//----------------------------------------------------------------------------------------
void calc_sth11(float *p_humidity ,float *p_temperature)
//----------------------------------------------------------------------------------------
// calculates temperature [C] and humidity [%RH]
// input : humi [Ticks] (12 bit)
// temp [Ticks] (14 bit)
// output: humi [%RH]
// temp [C]
{ const float C1=-4.0; // for 12 Bit
const float C2= 0.0405; // for 12 Bit
const float C3=-0.0000028; // for 12 Bit
const float T1=0.01; // for 14 Bit @ 5V
const float T2=0.00008; // for 14 Bit @ 5V
float rh=*p_humidity; // rh: Humidity [Ticks] 12 Bit
float t=*p_temperature; // t: Temperature [Ticks] 14 Bit
float rh_lin; // rh_lin: Humidity linear
float rh_true; // rh_true: Temperature compensated humidity
float t_C; // t_C : Temperature [C]

t_C=t*0.01-40; //calc. Temperature from ticks to [C]

rh_lin=C3*rh*rh + C2*rh + C1; //calc. Humidity from ticks to [%RH]

rh_true=(t_C-25)*(T1+T2*rh)+rh_lin; //calc. Temperature compensated humidity [%RH]

if(rh_true>100)rh_true=100; //cut if the value is outside of

if(rh_true<0.1)rh_true=0.1; //the physical possible range

*p_temperature=t_C; //return temperature [C]
*p_humidity=rh_true; //return humidity[%RH]
}


//--------------------------------------------------------------------
float calc_dewpoint(float h,float t)
//--------------------------------------------------------------------
// calculates dew point
// input: humidity [%RH], temperature [C]
// output: dew point [C]
{ float k,dew_point ;

k = (log10(h)-2)/0.4343 + (17.62*t)/(243.12+t);

dew_point = 243.12*k/(17.62-k);

return dew_point;
}

//----------------------------------------------------------------------------------
void main()
//----------------------------------------------------------------------------------
// sample program that shows how to use SHT11 functions
// 1. connection reset
// 2. measure humidity [ticks](12 bit) and temperature [ticks](14 bit)
// 3. calculate humidity [%RH] and temperature [C]
// 4. calculate dew point [C]
// 5. print temperature, humidity, dew point


//AD1PCFGbits.PCFG0=1;
//AD1PCFGbits.PCFG1=1;
{
AD1PCFG =0XFFFF;
//AD1PCFGbits.PCFG10=1;



value humi_val,temp_val;

float dew_point;
unsigned char error,checksum;
//unsigned int i;

char temp[13];
char humi[13];


// Initlcd(); //Initialize LCD

s_connectionreset();
delay_ms(20);

while(1)
{

error=0;

error+=s_measure((unsigned char*) &humi_val.i,&checksum,HUMI);
//measure humidity

error+=s_measure((unsigned char*) &temp_val.i,&checksum,TEMP);
//measure temperature

if(error!=0)
{
s_connectionreset(); //in case of an error: connection reset
}
else
{
humi_val.f=(float)humi_val.i; //converts integer to float
temp_val.f=(float)temp_val.i; //converts integer to float

calc_sth11(&humi_val.f,&temp_val.f); //calculate humidity, temperature

dew_point=calc_dewpoint(humi_val.f,temp_val.f); //calculate dew point

//send final data to serial interface (UART)

// Lcd8_Out(1,1,Out_temp());
// Lcd8_Out(2,1,Out_humi());
//
// FloatToStr(temp_val.f, temp);
// Lcd8_Out(1,6,temp);
//
// FloatToStr(humi_val.f, humi);
// Lcd8_Out(2,6,humi);


}
//----------wait approx. 0.8s to avoid heating up SHTxx----------------------
//-----------------------------------------------------------------------------------
delay_ms(1000);

}

}

Sorry jalpa I did not either realize that the sensor is not I2C...

Check this:

- Put a break point in line:

      error=DATA; //check ack (DATA will be pulled down by SHT11)

Check Data value in the physical Line SDA,

     if 'low', sensor is responding, so put a break point in line

               if(DATA) error+=1; // or timeout (~2 sec.) is reached

               Check what was the reason of exit the previous loop, i gets 65536 or D==0, if i gets 65536 the sensor does not end the measurement (remember using Pull-up resistor)

     if 'high', sensor is not responding:

               - Can you debug your code step by step? (in MPLAB I recommend you using F7 step into, because it is the shortest step). If yes run again the code from the begining, and when start the transmission of the command:

for (i=0x80;i>0;i/=2) //shift bit for masking

{ if (i & value) DATA=1; //masking value with i , write to SENSI-BUS

else DATA=0;

SCK=1; //clk for SENSI-BUS

delay_us(5); //pulswith approx. 5 us

SCK=0;

}

check every time that the status of both lines SCK and SDA are what you are expecting. When the command is sent keep on stepping and check the status of SDA when you get to line

error=DATA; //check ack (DATA will be pulled down by SHT11),

If now SDA is low means that sensor works, so maybe it is timing problem,

Check this, and let us know what you get.

Sorry for not giving a more concise answer but without the board and the sensor is difficult to try the code...

Regards.

hi..

i am using the pic24f16ka102 and temperature sensore tmp75 i got the same problem that i got the acknowledge for address but did'nt get the acknowledgement for data