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hobby_85
Joined: 17 Aug 2009
Posts: 50
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| What am I doing wrong? |
 Posted: Fri Aug 21, 2009 9:20 pm |
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I bought a RF kit, transmitter and receiver, and the website of a similar product is below. Now, I'm trying to write code for it, just to make sure it is working.
http://www.sparkfun.com/commerce/product_info.php?products_id=8950
I'm using a PIC 16f688 and if the LED lights up to a correct pattern, I know the code is working. However, it is not.
Here is the TX code:
| Code: |
#include <16F688.h>
//---------------------------------------------------------
#define WireTX PIN_C4 //
#define WireRX PIN_C5
//---------------------------------------------------------
#fuses XT, NOWDT, NOPROTECT,NOBROWNOUT, PUT
#use delay (clock = 4000000)
#use rs232(baud=2400,xmit=WireTX , rcv=WireRX , STREAM=COM_A )
void main(){
for(;Wink{
if(input(PIN_C2)==0) //if button pressed
{
output_high(PIN_A1); //output high Led
delay_ms(20); //delay 20ms
fputc('T',COM_A); //send data
delay_ms(20);
delay_ms(1000); //delay some ms
output_low(PIN_A1); // output low led
}
output_high(PIN_A1); // if button not pressed then just on off led on pin D1
delay_ms(50);
output_low(PIN_A1);
delay_ms(50);
}
} |
So if the button is pressed, the letter T is meant to be sent across, and the LED should come on, then off then on a longer time.
Here is the corresponding Receiver code:
| Code: |
#include <16F688.h>
#fuses XT, NOWDT, NOPROTECT,BROWNOUT, PUT
#use delay (clock = 4000000)
//------------------------------
#define WireTX PIN_C4
#define WireRX PIN_C5
//------------------------------
#use rs232(baud=2400, xmit=WireTX, rcv=WireRX, STREAM=COM_A)
unsigned int8 data;
int1 flag=0;
#int_rda
void rd_isr(void){
disable_interrupts(INT_RDA); // Disable Serial Recieve Interrupt
disable_interrupts(GLOBAL); // Disable Global Interrupts
data= fgetc(COM_A);
if(data=='T'){
flag=1;
}
enable_interrupts(GLOBAL);
enable_interrupts(INT_RDA);
}
void main(){
enable_interrupts(global);
enable_interrupts(int_rda);
for(;Wink{
if(flag==1){
output_high(PIN_A1);
delay_ms(1000);
output_low(PIN_A1);
flag=0;
}
output_high(PIN_A1);
delay_ms(50);
output_low(PIN_A1);
delay_ms(50);
}
} |
So if the message is received, the LED should come on/off in 1 sec intervals. If not, it should just flash on and off.
I have an oscilloscope, so I can look at the signals being transmitted. Here are the problems:
1) The switch - When I checked the RF signal being sent when the button was pushed, I saw a step on the oscilloscope. The message would be sent forever and the led would light as coded, as long as the button was pushed.
So I know something was sent across. However, after a couple of seconds, even when the switch was off, the message was sent automatically.
I have connected a 220k resister from the output of the MC to the LED, and then to GND.
2) The receiver - The led turns on/off, as though it didn't receive anything. However, when I connected the osc to the receiver/RX of the MC, I can see a jump in the signal, matching the signal sent by the tx. So why isn't the led lighting as expected?
Any ideas? The code itself is from the CCS library, and it works apparently.
Thanks |
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hobby_85
Joined: 17 Aug 2009
Posts: 50
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| Posted: Fri Aug 21, 2009 10:06 pm |
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update:
When I changed the RF receiver, the LED lights up as per normal...like its picking up a signal. However, I've bought about 5 RF transmitters and receivers, and somehow, the other receivers don't pick up the signal either. Just one is picking up the signal.
No clue what is happening here. Any ideas?
Please Help.
Thanks |
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hobby_85
Joined: 17 Aug 2009
Posts: 50
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| Posted: Fri Aug 21, 2009 10:20 pm |
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update:
I attached a small (10cm) antenna to the transmitter and now the receiver picks it up every few seconds. Even the tha transmitter sends out the signal continuously. It can sometimes go for a minute before it picks it up.
It looks like the receiver is picking up garbage copntinusoutly, and by fluke, it picks up the 'T' and lights the LED. Still don't have a concrete working circuit/code. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Aug 21, 2009 10:38 pm |
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| Quote: | #int_rda
void rd_isr(void){
disable_interrupts(INT_RDA);
disable_interrupts(GLOBAL);
data= fgetc(COM_A);
if(data=='T'){
flag=1;
}
enable_interrupts(GLOBAL);
enable_interrupts(INT_RDA);
} |
Delete the lines shown in bold. They are not needed. Nested interrupts
are not supported. The compiler and the PIC's hardware handle all of
this for you. Re-enabling Global interrupts inside an isr can cause
the program to crash, if an another interrupt occurs while you're still
inside the isr (because nested interrupts are not supported).
What is this ? Was part of the line cut off ? (in both Rx and Tx code) |
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hobby85
Guest
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| Posted: Fri Aug 21, 2009 11:26 pm |
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| hey pcm, thanks for replying. I'm on my phone so wont be able to write much. I will delete those lines like you said. The smiley is a mistake in copying and pasting. Its meant to be a for loop which goes forever. So for{;;} is what its meant to be. When I left home, I noticed that when I turned the switch on and off quickly, the receiver would pick up the signal and light the led properly. Almost all the time. But if the switch stayed on forever, meaning the signal is meant to be sent across in an infinite loop, then the receiver would pick up mostly noise but sometimes the signal too. When I mean sometimes, I mean once in like a minute. Do you think its because I'm not using any encoder or decoder? |
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hobby
Guest
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| Posted: Fri Aug 21, 2009 11:39 pm |
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| Also, sometimes a signal is being transmitted by the transmitter regardless of the switch is being pressed. Any ideas? Thanks all. |
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hobby_85
Joined: 17 Aug 2009
Posts: 50
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| Posted: Sun Aug 23, 2009 10:03 am |
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hey, can anyone point out the different between the two codes:
| Code: |
int data[9];
int STX = 0x02;
int CRC = 85; //85 chosen randomly for test purposes
int CR = 0x0d;
int counter = 0;
sprintf(data,"%x%x%x%xAAA%x%x",0,0,0,STX,CRC,CR);
while(counter<9){
fputc(data[counter],COM_A);
counter = counter+1;
}
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AND
| Code: |
fputc('0',COM_A);
fputc('0',COM_A);
fputc('0',COM_A);
fputc(STX,COM_A);
fputc('A',COM_A);
fputc('A',COM_A);
fputc('A',COM_A);
fputc(CRC,COM_A);
fputc(CR,COM_A);
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I'm trying to get the while loop working so I don't waste space and have extra lines, but nothing is being transmitted when I do. If I you fputc(), then it does.
Thanks all. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Aug 23, 2009 10:20 am |
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Debug it. Put in a printf statement just after your sprintf line to display
the contents of your 'data' buffer. Verify that it holds what you think it
should hold.
Then, consider the size of your 'data' buffer. You have a 9-byte buffer.
Of those, up to 8 can be used for chars, and one for the string terminator
byte of 0x00. How many bytes are represented by your format string in
the sprintf line ? I'll bet that it's a lot more than just 8 chars. To code
in C, you have to start being suspicious. Question your code. "What I
have I done that's possibly wrong here ?" Put in printf statements to
display intermediate values and prove that each line is working correctly. |
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