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dodang8811
Joined: 04 Mar 2014
Posts: 4
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| 16F688 INTERNAL CLOCK UART PROBLEM |
 Posted: Tue Mar 04, 2014 6:43 pm |
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This is my code but MCU sends wrong message.
| Code: |
#include <16F688.H>
#fuses INTRC_IO, NOWDT, NOBROWNOUT, PUT, NOMCLR
#use delay(internal=4M)
#use rs232(baud=9600,parity=N,xmit=PIN_C4,rcv=PIN_C5,bits=8)
#define PMIC_RST PIN_A2
//===========================================
void main()
{
for(;;)
{
putc('1');
putc('2');
putc('3');
putc('4');
putc('5');
putc('6');
putc('7');
putc('8');
putc('9');
putc('\n');
putc('\r');
//printf("hello\n");
delay_ms(1000);
}
}
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I wanna send
0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x0a,0x0d
( 1 2 3 4 5 6 7 8 9 \n \r)
but terminal received
0x39,0x32,0x33,0x36,0x35,0x36,0x37,0x3e,0x39,0xca,0xcd
( 9 2 3 6 5 6 7 > 9 ? ?)
And if I use
printf("hello\n");
it sends
" n e n n o ? "
How can I solve this problem? |
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Tue Mar 04, 2014 8:21 pm |
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It could be a 'timing' problem. The internal osc (currently 4MHz) could be off a bit, also since the internal osc can be selected as 8MHz, I'd use that.
2 options to try...
1) use a real 4MHz xtal (and 2 caps), alter code, recompile and test.
2) use your current setup but try 1200 Baud. Slower speeds tend to be more 'forgiving'.
You do have a 'max232' type interface chip between the PIC and PC ?
Another test is to remove PIC, jumper the TTL rx to the TTL tx pins and 'loopback' the PC terminal hardware to prove there's nothing wrong on that 'side' of the project.
Please post back what happens and we can help you from there.
hth
jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19504
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| Posted: Wed Mar 05, 2014 1:44 am |
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What voltage are you running the chip?. What temperature?.
The internal oscillator, on this chip, is guaranteed to be accurate enough for RS232, _if you are running at 3.5v_. Otherwise it 'may be accurate enough' at 5v and room temperature (but is getting borderline), but outside this, it is well outside the required accuracy.....
Best Wishes |
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dodang8811
Joined: 04 Mar 2014
Posts: 4
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| Thank you but I can't solve the problem yet. |
| Posted: Wed Mar 05, 2014 6:27 pm |
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First, I have 3 16f688 chips and the results are all same.
//temtronic
I'm using max3232 chip between PC and PIC.
All frequencies(1M, 2M, 4M, 8M...) sends wrong data.
1) I can't use xtal because the chip is in a product. It's smd type circuit and I can't change it.
2) 1200 Baud send worse data like "fe fe fe fe fe ...."
I can't understand why slower speed results are worse.
3) Loopback test is OK.
//Ttelmah
When I used 3.5V, I got worse data.
Please give me more advice~ |
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Wed Mar 05, 2014 7:18 pm |
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hmm..
well this is curious !!
I don't have a 16F688 so I 'white breadboarded' a 16F887 which has same/similar internal oscillator section, grabbed your code, made appropriate changes for the UART pins., and used the 887 device header file.
It works fine for me. I'm using Realterm for the PC terminal program and a TTL<>USB module for the interface.
Though it's a long shot, perhaps the fail-safe oscillator is enabled?
I would select the fuse 'NOFCMEN' though I didn't in my test.
Another question. Did you compile under MPLAB in 'debug' or 'release' mode?
If you compiled under 'debug'( the supplied default) , your code will NOT run correctly,usually slow.
I ran into this 'debug/release' issue a few years ago and my default is 'release' as I debug code in the real world not in simulations.
I'll keep the board up and running, but 'on the surface' I can't see anything wrong in your code or hardware setup.
hth
jay |
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dodang8811
Joined: 04 Mar 2014
Posts: 4
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| It works well on smd type. |
| Posted: Wed Mar 05, 2014 7:55 pm |
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Is smd type chip more accurate?
Actually, yesterday I tested on DIP type chip, breadboard and max3232.
And I tested on my product few minutes ago.
In the product, PIC sends data to CPU.
And I checked data from CPU. It's working well now.
"123456789", "hello"
I don't know why, but thank you very much for your concerning. |
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Wed Mar 05, 2014 8:14 pm |
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Glad it's up and running.
I'm always happy to help.
Jay |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Re: It works well on smd type. |
| Posted: Thu Mar 06, 2014 7:00 am |
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| dodang8811 wrote: | Is smd type chip more accurate?
Actually, yesterday I tested on DIP type chip, breadboard and max3232.
And I tested on my product few minutes ago.
In the product, PIC sends data to CPU.
And I checked data from CPU. It's working well now.
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Hi,
No, the package style itself would not explain your issue. My guess is that you have some sort of a wiring error on your breadboard!
John |
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dodang8811
Joined: 04 Mar 2014
Posts: 4
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| Thank you~! |
| Posted: Fri Mar 07, 2014 1:42 am |
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//ezflyr
Thanks. I'll test on a new breadboard and jumper later.
Have a good day~! |
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