Electromagnetic interference on PIC16F877A?

[narccizzo]

It's unbelievable that after ten months and still fighting with this little bastard, why don't you post the file.hex and I can have some fun too.

 

[chevymn1964]

I also seem to remember a few months ago, I was working on a project using serial comm and I made up the circuit on the ol' bread-board and I forgot to use the caps on the xtal... I was having the similar problems that you have.... so, try the caps and let us know..........

 

[mynickname101]

i have been suffering the last month from this wierd error...i even sometimes didn' hav a sleep for 2 days searching for the reason of this error...finally i fixed this problem 2day...i went to a doctor in the cairo engineering university and he told me to type in my programming(assembly) LVP=OFF (low voltage programming)....so try to type this command but i dunno hw it is written in ur programming launguage...hope tht ISALLAH could be ur problem solution

 

[saeed_pk]

Hi ,
I have read your problem and different Solutions by people;

I suggest you certain things to check,

- Check your Power Supply Pure 5VDC (no Ripples) and about 1A Current
- Check Regulator o/p Cap Is this creating any noise? unstable?
- Check whether you Connected MCLR pin High with pull up?
- Checkout your crystal and its Capaccitor. and its should have shortest leads.

If this system does not work then
Make a simple Program which toggles a PIN (1 Sec Delay) and see does it work
If it works
Problem may be with your Firmware?
otherwise your MCU is faulty if other things are OK
I hope you get a solution.

 

[ertug]

I think the problem might occur because of the lack of proper grounding around your circuits. I guess there is some looping in cables' assembly - that can be also affected by your movement. Although you have supply decoupling caps or any filtering components, those may not work well without proper grounding. I suggest you to combine GND pins of PIC and cap's negative pins together with a thick cable - such as multi-wired power cables.

 

[FL_KNV]

try powering the PIC from battery, also try to grab the data on scope, check the timing of waveform, also check the voltage level of uC serial port pins

 

[chevymn1964]

I think this guygave up on this project.......

 

[umery2k75]

No I didn't gave up. I don't get time, I'm overoccupied with work these days. I read all your comments daily.

Added after 12 minutes:

I have a project that has it's dead line nearby, I have got to work alot on it.I am working on it and I'm deciding about ARM evaluation board as which one to import these days. I already have import 2 of them, but they aren't flexible.I haven't switched on ARM MCU completely. It's really difficult to decide a MicroController as which one to work on and to which one to invest your money and on to their compiler and to their resources, there are hundreds of them and which will suits you the best for the areas you want it to work on.

 

[GregoryHouse]

Hi everyone

At first sorry for my language, becouse I'm not from england

I have the similar problem, which had umker2k75. I've built programmer PICs from site www dot cd2clone dot com. also when I touch him or bring closer ( my finger ) to pic diode usb on programmer - pic18f4550 has reset. Umker - you gave pull-up, but on my schematic pcb he is not exist. I dont understand it, but maybe someone can join this two problem, to help umker and me

regards

 

[are]

I have studied your problem.
you have a cap of 470uF on the power places on the print.
the max 232 has an internal dc converter that the power may influence.
if this does not help, you can use an external oscilator to ensure that these good works.

 

[umery2k75]

The circuit doesn't always start giving the ASCII output on serial interface, to check this up I set up two hardware on 2400 baud rate, the other green hardware on left always communicate, where as PIC communicates on 1/20 attempt in doing so, after downloading hex file into it and by checking up the serial output on HyperTerminal. I think this has to do with the Reset Circuit. I had put the 22pf Capacitor on the circuit and additionally I had changed the Crystal from 3.579545 to 20 Mhz. I used the 3.579545 crystal because its the only frequency at which the baud rate generator has the least error.

#include<16f877A.h>
#use delay (clock=20000000)
//#use delay (clock=03579545)
#fuses NODEBUG,HS,NOWDT,PUT,NOPROTECT,NOLVP

#use rs232(baud=2400,xmit=PIN_C6,rcv=PIN_C7)
main()
{
   int i;




   while(1) {
            i=65;
            do
               {
               putc(i);
               delay_ms(1000);
               i++;
               }
             while(i<=122);
            }
}

 

[ieddwin]

I used to have the same problem with my pic16f877a, it was having a lot interference each time that my hand was approaching over the crystal and annoying every time that I was touching any part of the printed board, so the solution at this noisy problem of interference finished when I connected a wire from the terminal negative of the (5vdc) to the metallic structure of the power supply.

problem solved.

other detail is that of the 3 pics 16f877a that i have,,the pin 6 (A4) doesn't work, I set it as output or input and doesn't work, but the rest of pins of the register A, B, C, D, E work good as input or output.

Does anybody got this issue before?


Thanks