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jrafa
Joined: 13 Dec 2012
Posts: 9
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| error with sensor SHT15 |
 Posted: Sat Jul 20, 2013 10:15 am |
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hi,
i am using a dspic30f6015 and a sensirion sht15. The pic is using the internal rc oscillator of 7.370.000 Hz, the interface is PIN_D6 & D5 for DATA & CLK. The data line has a 10k resistor pullup, and there is a 0.1uF capacitor for power supply the sensor like datasheet recommends. All the system is powered from 5V. I am using mplab 8.88, ccs 4.138 and pickit2 (also as power supply).
I can see the activity of the lines with a oscilloscope, but only when the microcontroller writes. The sensor doesn't response, there is not ACK or data from the SHT. The power of the sensor is ok.
The code is based on the sensirion example and libraries from this forums:
| Code: |
#include <30F6015.h>
#FUSES WPSA8 //Watch Dog Timer PreScalar A 1:64
#FUSES WPSB1 //Watch Dog Timer PreScalar B 1:16
#FUSES FRC //Internal Fast RC Oscillator
#FUSES NOPUT //Clock Switching is enabled, fail Safe clock monitor is enabled
#FUSES NOBROWNOUT //No brownout reset
#fuses NOWDT,NOPROTECT
#use delay(clock=7370000)
#include "temp.h"
void main(){
delay_ms(1000);
initTemp();
delay_ms(1000);
while(1){
readTemp();
delay_ms(1000);
}
}
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temp.h is:
| Code: |
#include <math.h>
typedef union {
long i;
float f;
unsigned int8 b[4];
} t_value;
enum {TEMP, HUMI};
#define DATA PIN_D6
#define SCK PIN_D5
#define noACK 0
#define yesACK 1
#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
t_value humi_val, temp_val;
char s_write_byte(char value){
char i, error = 0;
for (i = 0x80; i > 0; i /= 2){
if (i & value){
output_high(DATA); // DATA=1; //masking value with i , write to SENSI-BUS
}else{
output_low(DATA); //DATA=0;
}
delay_us(2);
output_high(SCK); //SCK=1; //clk for SENSI-BUS
delay_us(6); //_nop_();_nop_();_nop_(); //pulswith approx. 5 us
output_low(SCK); //SCK=0;
delay_us(2);
}//fin for
output_high(DATA); //DATA=1; //release DATA-line
delay_us(2);
output_high(SCK); //SCK=1; //clk #9 for ack
output_float(DATA);
error = input(DATA); //DATA; //check ack (DATA will be pulled down by SHT11)
output_low(SCK); //SCK=0;
return(error); //error=1 in case of no acknowledge
}
char s_read_byte(char ack){
char i, val=0;
output_high(DATA); //DATA=1; //release DATA-line
for (i = 0x80; i > 0; i /= 2){
output_high(SCK); //SCK=1; //clk for SENSI-BUS
if (input(DATA)){
val = (val | i); //read bit
}
output_low(SCK); //SCK=0;
}
output_bit(DATA, !ack); //in case of "ack==1" pull down DATA-Line
delay_us(2); //observe setup time
output_high(SCK); //clk #9 for ack
delay_us(6); //pulswith approx. 5 us
output_low(SCK);
delay_us(2); //observe hold time
output_high(DATA);
return val;
}
void s_transstart(void){
output_high(DATA); // DATA=1;
output_low(SCK); // SCK=0; //Initial state
delay_us(2); // _nop_();
output_high(SCK); // SCK=1;
delay_us(2); // _nop_();
output_low(DATA); // DATA=0;
delay_us(2); // _nop_();
output_low(SCK); // SCK=0;
delay_us(6); // _nop_(); _nop_();_nop_();
output_high(SCK); // SCK=1;
delay_us(2); // _nop_();
output_high(DATA); // DATA=1;
delay_us(2); // _nop_();
output_low(SCK); // SCK=0;
}
void s_connectionreset(void) {
char i;
output_high(DATA); // DATA=1;
output_low(SCK);
for(i = 0; i < 9; i++){ // 9 SCK cycles
output_high(SCK); // SCK=1;
delay_us(2);
output_low(SCK); // SCK=0;
delay_us(2);
}
s_transstart(); //transmission start
}
char s_measure(char *p_value, char *p_checksum, char mode){
char error = 0;
long i;
s_transstart(); //transmission start
switch(mode){ //send command to sensor
case TEMP:
error += s_write_byte(MEASURE_TEMP);
break;
case HUMI:
error += s_write_byte(MEASURE_HUMI);
break;
default:
break;
}
output_float(DATA);
for (i = 0; i < 65535; i++){
delay_us(2);
if(input(DATA) == 0){
break; //wait until sensor has finished the measurement
}
}
if(input(DATA)){
error += 1; // or timeout (~2 sec.) is reached
}
*(p_value) = s_read_byte(yesACK); //read the first byte (MSB)
*(p_value+1) = s_read_byte(yesACK); //read the second byte (LSB)
*p_checksum = s_read_byte(noACK); //read checksum
return(error);
}
void initTemp(){
humi_val.f = 0.0;
temp_val.f = 0.0;
output_float(DATA);
output_float(SCK);
s_connectionreset();
}
void readTemp(){
char checksum, error = 0;
error += s_measure((char*) &humi_val.i, &checksum, TEMP); //measure humidity
error += s_measure((char*) &temp_val.i, &checksum, HUMI); //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
}//fin if else
}
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The first error is at the s_write_byte() function because there is not ACK from the sensor.
Can someone help me solve this problem?
Thanks.
Best regards. |
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temtronic
Joined: 01 Jul 2010
Posts: 9244
Location: Greensville,Ontario
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| Posted: Sat Jul 20, 2013 11:25 am |
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The driver 'temp.h' has a comment about the sht11 device, yet you're using an sht15.
Have you carefully read the datasheets for both devices, and noted ANY differences with respect to timing, configuration, commands,electrical specs.,etc.?
You may have a 'compatibilty' problem as it appears the driver was written for the SHT11 device.
hth
jay |
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jrafa
Joined: 13 Dec 2012
Posts: 9
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| Posted: Sat Jul 20, 2013 11:47 am |
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Thank you for your quick response.
The datasheet only shows differences on accuracy and packaging between sht10, sht11 and sht15. The inferface specifications are equivalents.
Best regards. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19545
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| Posted: Sat Jul 20, 2013 12:32 pm |
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Two things in the data sheet might be worth noting.
1) Comment that wires/connections longer than 10cm (4"), may result in loss of communication, if Sck, and Sdata are close together.
2) Requirement that the power rail must rise faster than 1v/msec.
Best Wishes |
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Mon Jul 22, 2013 7:38 am |
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http://www.ccsinfo.com/forum/viewtopic.php?t=28564
That driver works with the SHT15... I tested it with a 16f886...
works just fine. i just modified the output to my needs...
G.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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jrafa
Joined: 13 Dec 2012
Posts: 9
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| Posted: Mon Jul 22, 2013 8:57 am |
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Ttelmah, i appreciate your interest. The traces are 55.92 mm (CLK) and 54.09 mm (DATA). The power supply needs over 300us for rising 5V.
Gabriel, I saw this thread, but did not use it because it was for the sht71. I've tried and it works!.
thank you very much |
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Mon Jul 22, 2013 10:07 pm |
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glad to help..
G.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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