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asiklariskostas
Joined: 07 Jul 2013
Posts: 16
Location: Greece
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| DHT22 - PIC 24FJ64GA002 |
 Posted: Mon Nov 11, 2013 9:21 am |
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Hello everyone. I need your help with DHT22 sensor and PIC24FJ64GA002. According to a previous topic, i tried to compile your code to my project, but my hyperterminal is blank - i don't receive any messages. Can anyone help me??? Thanks anyway!!!
I use PCWHD Compiler (version 5.008).
Here is the program that i've made:
| Code: |
#include <24fj64ga002.h>
#include <stdio.h>
#FUSES NOWDT //No Watch Dog Timer
#FUSES NOJTAG //JTAG disabled
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOWRT //Program memory not write protected
//#FUSES DEBUG //Debug mode for use with ICD
#FUSES ICSP1 //ICD uses PGC1/PGD1 pins
#FUSES NOWINDIS //Watch Dog Timer in Window mode
#FUSES WPOSTS16 //Watch Dog Timer PostScalar 1:32768
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES PR //Primary Oscillator
#FUSES NOCKSFSM
#FUSES NOOSCIO //OSC2 is clock output
#FUSES HS //Crystal osc <= 4mhz for PCM/PCH , 3mhz to 10 mhz for PCD //Internal External Switch Over mode disabled
#FUSES WUT_DEFAULT
#FUSES WPOSTS1 //Watch Dog Timer PostScalar 1:1
#use delay(xtal=16000000)
#use rs232(baud=9600, xmit=PIN_A0, rcv=PIN_A1,bits=8)
int bExit;
int DHT_Data;
int iByteIndex;
int CRC;
void DHT_Start(void)
{
// Here we send the 'start' sequence to the DHT sensor! We pull the DHT_IO pin low for 25mS, and
// then high for 30mS. The DHT sensor then responds by pulling the DHT_IO pin low, and then pulling it
// back high.
Output_low(PIN_B3);
delay_ms(25);
Output_high(PIN_B3);
delay_us(30);
// Here we wait while the DHT_IO pin remains low.....
bExit = False;
set_timer2(255);
while (!input(PIN_B3) && !bExit);
// Here we wait while the DHT_IO pin remains high.....
bExit = False;
set_timer2(255);
while (input(PIN_B3) && !bExit);
}
int8 DHT_ReadData(void)
{
// This subroutine reads a byte of data (8 bits) from the DHT sensor...
int8 iIndex;
int8 iValue = 0;
for(iIndex = 0; iIndex < 8 ; iIndex++)
{
bExit = False;
set_timer2(255);
while (!input(PIN_B3) && !bExit);
delay_us(30);
if (input(PIN_B3))
{
iValue = iValue |(1<<(7 - iIndex));
bExit = False;
set_timer2(255);
while (input(PIN_B3) && !bExit);
}
}
return iValue;
}
void main()
{
// Here we send the initialization sequence to "wake up" the DHT sensor, and put it into
// data transmission mode.
DHT_Start();
int i;
// Here we read a total of 5 bytes of data (40 bits) from the DHT sensor. For the DHT-11 sensor,
// the integer data is contained in the 1st (Humidity), and 3rd (Temperature) bytes transmitted,
// and the 2nd and 4th decimal bytes are always zero (0). For the DHT-22 sensor, the integer data is
// is contained in the 1st (Humidity), and 3rd (Temperature) bytes transmitted, and the decimal
// data is contained in the 2nd (Humidity), and 4th (Temperature) bytes transmitted. The 5th byte
// contains the CRC byte for both sensor types.
for (i = 0; i < 5 ; i++)
{
DHT_Data(i) = DHT_ReadData();
}
// Here we calculate the CRC by adding the 1st four bytes, and looking at only the lower 8 bits.
// This value should match the 5th byte sent by the sensor which is the CRC byte!
CRC = DHT_Data[0] + DHT_Data[1] + DHT_Data[2] + DHT_Data[3];
CRC = CRC & 0xFF;
if (CRC != DHT_Data[4] && !bExit)
fprintf(PC, "CRC Error, expected: %Lu, and received: %u\n\r", CRC, DHT_Data[4]);
if (bSensorType == DHT11)
{
Humidity = DHT_Data[0];
Temperature = DHT_Data[2];
//fprintf(PC, "Humidity: %ld%%\n\r", Humidity);
//fprintf(PC, "Temperature: %ldC\n\r", Temperature);
}
else
{
Humidity = Make16(DHT_Data[0], DHT_Data[1]);
Temperature = Make16(DHT_Data[2] & 0x7F, DHT_Data[3]); //Strip off the sign bit first!
//Temperature /= 10;
if (DHT_Data[2] & 0x80)
Temperature *= -1;
//fprintf(PC, "Humidity: %3.1w%%\n\r", Humidity);
//fprintf(PC, "Temperature: %3.1wC\n\r", Temperature);
}
} |
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temtronic
Joined: 01 Jul 2010
Posts: 9226
Location: Greensville,Ontario
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| Posted: Mon Nov 11, 2013 10:42 am |
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Since you're not receiving any messages, it sounds like a communications problem.
Start with a simple 'hello world' program to get the serial stuff right.
Simple things like...
1) proper RS232 xcvr( like MAX232) connected right ?
2) proper connections to PC(pin 2 is rcv, 5 is ground if DE9 connector)
3) PIC running at correct speed? The 1Hz flashing LED program will confirm this...
4) disable any and all peripherals that may be connected to the I/O pins you're using.ADC,PWM,etc...must be turned off.
5) confirm that Hyprerterminal is running. simple wire from pin 3 to pin 2 creates a 'loopback.press a key it MUST be displayed on screen,if not,well there's a huge problem that must be solved.
You have to program in 'steps'.Confirm the simple things work BEFORE you cut your main code.
hth
jay |
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