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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| ex_crc.c question |
 Posted: Mon Jan 15, 2007 5:28 pm |
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Hi,
I am implementing this example verbatim. I am using a 18F2680 but pin assignments are the same for this example.
In main .. interrupts are enabled :
| Code: |
ext_int_edge(H_TO_L); // init interrupts
enable_interrupts(INT_EXT);
enable_interrupts(GLOBAL);
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and the int_ext isr function is:
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#INT_EXT
void ext_isr()
{
ext_buffer[ext_buffer_next_in] = getc(); // get a byte, put it in buffer
if(++ext_buffer_next_in == BUFFER_SIZE) // increment counter
ext_buffer_next_in = 0;
}
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my TX PIC will hang at the interrupt at the getc() .. but I don't understand why what is causing the interrupt .. i tried disconnecting the wires to the interrupt pins B2-B0 but still it hangs .. then eventually it continues ??
thoughts? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jan 15, 2007 6:07 pm |
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Make certain that pin B0 is set as a digital pin. Use the NOPBADEN fuse
to make Port B come up as all digital at power-on reset. |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Mon Jan 15, 2007 6:11 pm |
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| Quote: |
my TX PIC will hang at the interrupt at the getc()
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1) How did you determine that the program hang in getc ?
2) To stay in getc implies that the interrupt was triggered by a falling signal but
the expected character never end arriving.
3) Pls tell us what kind of data are you receiving.
4) Pls tell us something regarding your hardware in the Rx path.
Humberto |
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Mon Jan 15, 2007 7:02 pm |
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| Humberto wrote: | | Quote: |
my TX PIC will hang at the interrupt at the getc()
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1) How did you determine that the program hang in getc ?
2) To stay in getc implies that the interrupt was triggered by a falling signal but
the expected character never end arriving.
3) Pls tell us what kind of data are you receiving.
4) Pls tell us something regarding your hardware in the Rx path.
Humberto |
1) in the isr routine i placed output_high(pin_A1) before the getc line on one build and it goes high and then after the getc line in another build and it won't go high .. so i figured that getc was blocking
2) ya .. my question is why did the interrupt trigger in the transmitting pic when it is the only one sending characters
3) the data that is being passed to the receive pic is from the example
| Code: |
packet_buffer[0] = SEND_ADDRESS;
packet_buffer[1] = MACHINE_ADDRESS;
packet_buffer[2] = 0;
packet_buffer[3] = 0;
packet_buffer[4] = 9;
packet_buffer[5] = 'H';
packet_buffer[6] = 'i';
packet_buffer[7] = ' ';
packet_buffer[8] = 't';
packet_buffer[9] = 'h';
packet_buffer[10] = 'e';
packet_buffer[11] = 'r';
packet_buffer[12] = 'e';
packet_buffer[13] = '!';
send_packet(packet_buffer, 14); // send message
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4) from the TX pic to the RX pick B0 goes to B1 and B1 goes to B0 .. just a straight line .. they also have common ground
---
Also, it seems that the RX pic is resetting when it gets to this line in the ex_crc.c example:
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if(get_packet(packet_buffer)) // if valid packet
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i say that it resets because i have and LED that blinks once at turn on and it continues to blink
thanks for the help .. i will try the other suggestion as well |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Mon Jan 15, 2007 7:39 pm |
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According to your description I guess you would have a problem regarding the
power pins, faulty GND, decoupling capacitors not present, noisy power supply and/or
something wrong in the Reset circuit path.
I would include the restart_cause() control function, in this device
it will give you up to 7 reason.
Sorry for not being more concise. I only can give you just some tips for focusing the
problem.
Humberto |
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Ttelmah
Guest
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| Posted: Tue Jan 16, 2007 6:00 am |
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What is the #USE_RS232 defintion for the getc?...
Best Wishes |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Tue Jan 16, 2007 6:43 am |
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| Quote: |
2) ya .. my question is why did the interrupt trigger in the transmitting pic when it is the only one sending characters
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Does the receiver is echoing something while receiving ?
Humberto |
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Tue Jan 16, 2007 6:47 am |
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| Ttelmah wrote: | What is the #USE_RS232 defintion for the getc?...
Best Wishes |
From the ex_crc.c example in the example folder the #use rs232 line for pic to pic comm is
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#use rs232(baud=9600, xmit=PIN_B1, rcv=PIN_B0)
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Tue Jan 16, 2007 6:50 am |
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| Humberto wrote: | | Quote: |
2) ya .. my question is why did the interrupt trigger in the transmitting pic when it is the only one sending characters
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Does the receiver is echoing something while receiving ?
Humberto |
Actually yes .. the RX pic is supposed to send back a NACK or ACK etc .. but still the interrupt in the TX pic gets tripped but then it gets stuck at the getc waiting for a character (or this is what i surmise)
but it still hangs even if there is nothing connected to the TX/RX (B0/B1) pins on the TX pic |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Tue Jan 16, 2007 6:56 am |
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| Quote: |
but it still hangs even if there is nothing connected to the TX/RX (B0/B1) pins on the TX pic
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Hook a 10K pull up in PIN_B0.
Humberto |
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Tue Jan 16, 2007 7:09 am |
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| I added output_low(pin_B0) and output_low(pin_B1) to both RX and TX chips and that seems to solve the issue .. pin B0 went high on the RX chip at turn on and caused the int on the TX |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Tue Jan 16, 2007 7:24 am |
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| Quote: |
So I put a 10k pull down resistor on B0 and that seems to correct the issue ..
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Good news! but it should be tied to +5V (pull up) not a pull down, according to your code:
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ext_int_edge(H_TO_L); // init interrupts
enable_interrupts(INT_EXT);
enable_interrupts(GLOBAL);
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Humberto
Edited: When I posted this answer the quoted phrase suddenly was changed.(???) |
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Tue Jan 16, 2007 7:49 am |
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ya .. i edited it bc the pull down did not work .. and rather what i put above did  |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Tue Jan 16, 2007 10:14 am |
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| Quote: |
added output_low(pin_B0) and output_low(pin_B1) to both RX and TX chips and that seems to solve the issue ..
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This is a weak argument, according to your definition PIN_B0 is an INPUT.
| Code: |
#use rs232(baud=9600, xmit=PIN_B1, rcv=PIN_B0)
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| Quote: |
pin B0 went high on the RX chip at turn on and caused the int on the TX
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This also is a weak argument, according to your definition PIN_B0 MUST BE High
when in idle state, and a falling down must trigger the INT_EXT.
| Code: |
ext_int_edge(H_TO_L);
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Don�t want to be offensive but this is like to do pitfall playing the solitaire... 
Humberto |
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pwhitey86
Joined: 11 Jan 2007
Posts: 9
Location: Philadelphia, PA, USA
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| Posted: Tue Jan 16, 2007 5:19 pm |
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ya .. humberto i took the statements out .. yes my reasoning was flawed
anyhow .. another question
currently I use pins b0 and b1 for RX TX .. is it possible to us b2 as say another RX pin since it is also an interrupt capable pin on the 18F2680?
ie can i do this
| Code: |
#use rs232(baud=9600, xmit=PIN_B1, rcv=PIN_B2)
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i tried but it's not working out .. keeps hanging in the interrupt.
.. and one more .. can I change the rcv pin in main()?
thanks |
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