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Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
this is my first pic project so i built a simple program that blinks a bunch of led's connected with bc550 transistors. RA0-RA3 are connected to led's that each go to one letter of my cousin Joey but in led's(see picture)and RB0-RB5 are connected directly to 6 low power ultrabright blue led's(one on each port)that i made flash around the border of my name. The oscillattor is a 10mhz resonater. when i got it all together and powered it up it worked like a charm for about 2-3 seconds and than stopped. i realised after a bunch of poking around that when i touch MCLR and RA4 with my finger it started to work again but after a couple of seconds it stopped. I am really puzzeled so if anyone has any tips plz let me know. Here is the program that works fine on my dev board when using 1 led for each letter and the led's on portB are steady and not flashing(same as in the real thing) the code is in basic
main: TRISA = 0 TRISB = 0 PORTA = %00000001 PORTB = %00111111 delay_ms(300) PORTA = %00000011 delay_ms(300) PORTA = %00000111 delay_ms(300) PORTA = %00001111 delay_ms(300) PORTA = %00000000 delay_ms(200) PORTA = %00001111 delay_ms(200) PORTA = %00000000 delay_ms(200) PORTA = %00001111 delay_ms(200) PORTA = %00000000 delay_ms(200) PORTA = %00001111 delay_ms(200) PORTA = %00000000 delay_ms(200) PORTA = %00001111 delay_ms(200) PORTA = %00000000 delay_ms(200) PORTA = %00001111 delay_ms(300) PORTA = %00001110 delay_ms(300) PORTA = %00001100 delay_ms(300) PORTA = %00001000 delay_ms(300) PORTA = %00000000 delay_ms(300) goto main end.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
You are correct, it should be pulled high. It is an active low input.
Usually connecting it directly to VDD in simple circuits like this is fine, but there are some cases where it will not be good enough. Using a resistor fixes most problems but in some cases a delay circuit must be made to make sure the PSU and oscillator is stable before the chip comes out of reset to make sure it does not lock up.
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
If fidgeted with pics before and most have an internal reset system, as for the code...................If ur using basic ur Delay should be "pause X" where pause is the # of milliseconds u want it to pause for. If not just listen to bjorn, he's more informed then I am, also I haven't messed with pics in 2 years...
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Also MCLR is vulnerable to ESD, be very careful! i've had this problem and it can cause random lockups. the fix is to put a 15v zener across this pin if using the chip in an ICSP or other application.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
WhiteArc wrote ...
If fidgeted with pics before and most have an internal reset system, as for the code...................If ur using basic ur Delay should be "pause X" where pause is the # of milliseconds u want it to pause for. If not just listen to bjorn, he's more informed then I am, also I haven't messed with pics in 2 years...
It looks like Mikrobasic to me, in which case his syntax is ok.
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pic16f84a stops running HELP!!!!
