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sridevi
Joined: 22 Apr 2014
Posts: 4
Location: Chennai
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| 18F252 not passed LED test [Solved] |
 Posted: Sat Jul 26, 2014 12:27 am |
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Hi,
I tried to do a LED blinking test using PIC18f252.
PIC18f252 with 8MHz crystal and 22pf capacitors. LED is connected to PORT A.1. Below is my coding.
| Code: | #include <18F252.h>
#FUSES NOWDT
#FUSES HS
#FUSES NOBROWNOUT
#FUSES NOLVP
#use delay(clock=8000000)
void main()
{
SETUP_ADC_PORTS(NO_ANALOGS);
SET_TRIS_A(0);
OUTPUT_LOW(PIN_A1);
while(true)
{
OUTPUT_LOW(PIN_A1);
delay_ms(1000);
OUTPUT_HIGH(PIN_A1);
delay_ms(1000);
}
}
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It is successfully compiled. When I run in real time, initially LED is ON as expected. After that it is not blinking.
Please help to resolve this issue. If I miss any statement, guide me.
Regards with advance thanks. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Sat Jul 26, 2014 1:24 am |
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Obvious thing, same problem as another poster only a couple of days ago here. MCLR not pulled up?.
The chip does also need both Vss connections, and a good decoupling capacitor close to the chip.
Then obvious tests on the actual voltage on Vdd.
Compiler version number?. |
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sridevi
Joined: 22 Apr 2014
Posts: 4
Location: Chennai
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| 18F252 not passed LED test |
| Posted: Mon Jul 28, 2014 3:11 am |
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MCLR pulled up via 10K resistor and Vss are properly grounded. 0.1 micro farad disc capacitor is used for decoupling and Vdd voltage is +4.98V.
CCS compiler version - PCWHD 4.140
Thanks. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Mon Jul 28, 2014 4:15 am |
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I'd be going over the board with a magnifying glass, looking for a whisker short, or a pad that is not making contact. Then do the same with a meter. Check for shorts between adjacent pads, and between pads and any track passing nearby. You almost certainly have a hardware problem. Could be an component being faulty (crystal etc.), or something silly, like you accidentally picked up 22nF capacitors, not 22pF. Given that these are basically identical in size when using small ceramics, it's easy to do.
When you program, make sure the programmer is set to write the fuses as well as the code, and that it does verify back correctly. |
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temtronic
Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario
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| Posted: Mon Jul 28, 2014 5:03 am |
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another possibility is that if using MPLAB that you haven't changed the 'build configuration' from 'debug' to 'release'. This must be done before you compile(F10), then download code into the PIC.
hth
jay |
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sridevi
Joined: 22 Apr 2014
Posts: 4
Location: Chennai
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| 18F252 not passed LED test |
| Posted: Mon Jul 28, 2014 10:27 pm |
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Dear All,
The thing is, if I write the code in MicroC for the same hardware set up, it is working well. So, I suspect the issue is in software. Am I missed any port configuration. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jul 28, 2014 11:41 pm |
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I made your program work with an 18F452. I plugged the PIC into a
PicDem2-Plus board (old style) and also plugged in an 8 MHz crystal.
The board has leds on pins B0-B3, so I installed a jumper wire from
pin A1 to pin B1. It runs. It blinks the LED. This test was done with
compiler vs. 4.140, the same as yours. I think you have a hardware
problem.
One question is, do you have a series resistor on the LED ? It's essential.
You can use anything from 220 to 1K ohms, and it should work. The
PicDem2-Plus board uses 470 ohms. Example of schematic:
| Code: |
pin 470 ohms LED
A1 -----/\/\/\/------->|----
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----- Ground
---
- |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Tue Jul 29, 2014 2:33 am |
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He says his LED is initially on. With the output_low() first this suggests he has the LED connected to +5V like: | Code: | O +5V
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pin 470 ohms LED |
A1 -----/\/\/\/-------|<---- |
Which of the two circuits are you using?
I still didn't see a response to Temtronic's good remark about MPLAB. So again, are you using MPLAB?
Still, very strange. Not reaching the set_tris_a() function would mean the A1 pin is configured as a high impedance input and the LED would be off.
With the LED switching on it means we get to the set_tris_a() function and then the whole program should work fine as there are no other 'difficult' things after that.
This suggests a hardware problem or the program as posted is not what is used in the hardware (not having the second delay_ms() line is a classic). |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Tue Jul 29, 2014 2:41 am |
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| I'd suspect Temtronic's suggestion as the 'most likely'. If the chip in in debug mode, and there is nothing connected to the ICD pins, the chip will probably float to 'halt'... |
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sridevi
Joined: 22 Apr 2014
Posts: 4
Location: Chennai
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| 18F252 not passed LED test |
| Posted: Tue Jul 29, 2014 4:01 am |
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another possibility is that if using MPLAB that you haven't changed the 'build configuration' from 'debug' to 'release'. This must be done before you compile(F10), then download code into the PIC.
That is the thing happened. I change the build config to Release mode now. It is working.
Thanks to All. |
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temtronic
Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario
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| Posted: Tue Jul 29, 2014 5:44 am |
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GREAT News !!! Please edit your subject line to include 'SOLVED' in it. That way others who read it will know it was solved and can bypass it if they want to.
You can change the default of the build configuration to 'release' if you want. The Microchip guys sent me a 'patch' to an earlier version as I never use 'debug' mode and it drove me nuts having to change it all the time.I've always 'debugged' in the real world.Cut code,burn the PIC, test and repeat as required.
cheers
Jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Tue Jul 29, 2014 7:39 am |
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As soon as the poster said the hardware was running with code from another compiler, I moved this from 'possible', to 'most likely', and (as you see), posted to say this.
It is one of those 'designed to catch you' annoyances.... |
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