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ibg
Joined: 19 Nov 2003
Posts: 22
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| Edge of Interruption II |
 Posted: Wed Apr 14, 2004 4:10 am |
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Hi,
As Humberto suggested me, it may be clearer if add the code 
| Code: | #include <18F452.h> // The device (PIC 18F452) include file
#device *=16 ADC=10
#include <string.h>
#use delay(clock=19660800) // Sets the speed for the PIC (itīs meausured in cycles per second)
#use fast_io(A) // Fast method of doing Input/Output
#use fast_io(B) // The direction register will be set later with the "set_tris_X()" instruction
#use fast_io(C)
#use fast_io(D)
// I/O ports are mapped in memory (Have a look to the Special Function Register (SFR) of PIC18F452)
#byte PORTA = 0xF80
#byte PORTB = 0xF81
#byte PORTC = 0xF82
#byte PORTD = 0xF83
#byte PORTE = 0xF84
#use rs232(baud=38400, xmit=PIN_C0, stream=DEBUG)
// Global variable
unsigned long digital_val= 0;
void init();
//----------------------------------------------------------------------------------
// This interruption service routine is executed when TD edge goes from H to L
#int_ext2
void ext_isr(void)
{
digital_val= read_adc();
fprintf(DEBUG,"Ext2 interruption --> Signal Strength= %lu\r\n", digital_val);
}
//----------------------------------------------------------------------------------
// Main program
void main(void){
init(); // Set the pin direction register and enable the interruptions
fprintf(DEBUG,"Start...\r\n");
while(1)
{
delay_ms(2000);
digital_val= read_adc();
fprintf(DEBUG, "loop --> %lu \r\n", digital_val);
}// end loop
}
//----------------------------------------------------------------------------------
// Initialisation routine
void init()
{
// SET_TRIS is necessary when using fast_io (in order to establish the pin direction)
// Remember:
// 1 -> in
// 0 -> out
SET_TRIS_A(0x01); // 0000 0001 (A0 analog input for the signal strength)
SET_TRIS_B(0x04); // 0000 0100 (B2 external interruption)
SET_TRIS_C(0x00); // 0000 0000
SET_TRIS_D(0x00); // 0000 0000
// Configure the AD converter
setup_adc(ADC_CLOCK_INTERNAL);
setup_port_a(ALL_ANALOG); // same as 'setup_adc_ports()'
set_adc_channel(0);
// Activate interruptions
ext_int_edge(2, H_TO_L);
enable_interrupts(int_ext2); // Enable rda (RS232 receive data available) interruption
enable_interrupts(GLOBAL); // It allows rda interruption to become active
}
/*EOF*/
//*********************************************************************************************
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The thing is that I get the same output with or witouth the instruction ext_int_edge(2, H_TO_L); I'm just interested in the falling edge.
Thanks for all,
Imanol |
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Humberto
Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata
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| Posted: Wed Apr 14, 2004 1:06 pm |
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Hi Imanol,
1) I think that the program is doing what it says, not what you expect.
2) What kind of signal is coming to RB2 EXT_INT2, it's a mechanical
switch debounced or a "clean single pulse"? Pull-ups ?
3) If you want to know/measure accurately an event, itīs not a good idea
to generate a printf inside an interrupt, it's better to generate a pulse
(microseconds wide) to see it on a scope or just toggle a led.
If you want to print such event, set a flag into the INT and print the
mssge in the main.
Regards,
Humberto |
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ibg
Joined: 19 Nov 2003
Posts: 22
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| More about the interruption edge |
| Posted: Thu Apr 15, 2004 12:46 pm |
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Hi,
The interruption is generated by a frequency receiver (used in telemetry studies) when detects the presence of a fish.
Anyway, I'm going to check once again how is the signal in an oscilloscope and see what's wrong.
Thanks for all,
Imanol
P.S: I continue open to new suggestions ;) |
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languer
Joined: 09 Jan 2004
Posts: 144
Location: USA
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RKnapp
Joined: 23 Feb 2004
Posts: 51
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| Posted: Fri Apr 16, 2004 1:55 am |
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But may I suggest that you also don't neglect the physical characteristics of the rising / falling edge. I've finally, finally, finally tracked a maddening problem of mine to EMI hitting the EXT1 pin and causing me to spuriously enter my INT_EXT1 interrupt routine. (Found it doing this on my scope, and added some pulldown resistors to clean up the line!)
The spurious interrupts were chewing up so much time -- all those pointless trips into an ISR -- that I was effectively crashed, and rebooted again and again, never the wiser about what had happened!
Robert |
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