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small_chick
Joined: 17 Jul 2012 Posts: 53
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UART problem in dsPIC30F4011 ? |
Posted: Fri Nov 23, 2012 10:29 am |
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I'd like to send only one character into Hyperterminal at each time writing into U2TXREG. But when I used the following code, it gave me 8 similar characters. I can't explain why this happened like that. I hope someone can help me ! i use a hardware crystal 10MHz.
Code: |
#include <30F4011.h>
#device PASS_STRINGS = IN_RAM
#fuses XT_PLL4,NOWDT,PUT64,BROWNOUT,BORV42
void main()
{
U2BRG = 64; //baurate = 9600
U2MODE=0x8000;
U2STA =0x0400;
while(UTXBF_2);
U2TXREG = 0x39;
while(1);
}
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temtronic
Joined: 01 Jul 2010 Posts: 9174 Location: Greensville,Ontario
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Posted: Fri Nov 23, 2012 2:32 pm |
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Generally speaking...manually setting up registers is not a 'good idea'.
99% of 'help' here uses the C compiler functions that CCS has designed/tested and supplies. They are known to work.
I, for one, have no idea if your assignments/values are correct and there probably aren't too many using the 30F series either.
Honestly, I'd try one of the examples CCS supplies for 'serial' communications, again, they are known to work and would be a good starting point/
hth
jay |
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small_chick
Joined: 17 Jul 2012 Posts: 53
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funny thing !!! |
Posted: Sat Nov 24, 2012 10:23 am |
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i think this problem is not easy to explain ! i've tried to use supported function by CCS and realize this interesting thing.
Compare two kind of coding following:
*1st case:
Code: |
#include <30F4011.h>
#device PASS_STRINGS = IN_RAM
#fuses XT_PLL4,NOWDT,PUT64,BROWNOUT,BORV42
#use delay(clock=40000000)
#use rs232(baud=9600,parity=n,bits=8,stop=1,uart2)
void main()
{
putc('a');
puts("chanh");
while(1);
}
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then the result is:
"achanh
achachaachaachanh
achachanh
"
(three lines in Hyperterminal as above)
*2nd case:
Code: |
#include <30F4011.h>
#device PASS_STRINGS = IN_RAM
#fuses XT_PLL4,NOWDT,PUT64,BROWNOUT,BORV42
#use delay(clock=40000000)
#use rs232(baud=9600,parity=n,bits=8,stop=1,uart2)
void main()
{
putc(getc());
putc('a');
puts("chanh");
while(1);
}
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then from the Hyperterminal, i type 1 character 'q' => the result is:"qachanh"
It seems like that dsPIC30F4011 need to receive before transmitting ! Hope you give some comments, maybe it's not a solution! just share our thoughts together ! ![Very Happy](images/smiles/icon_biggrin.gif) |
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gpsmikey
Joined: 16 Nov 2010 Posts: 588 Location: Kirkland, WA
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Posted: Sat Nov 24, 2012 10:58 am |
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Seems very odd - this is actual hardware you are running on and that is the entire code you show in your example ? What version of the compiler are you running ?
A couple of things come to mind to try assuming the above is true:
in the end "while" loop, add code to the loop at the end and see if the compiler does it differently ( while(1) {x=1;} ) or something like that that does nothing, but force the compiler to deal with it differently. You also should check the erata sheet for that chip and see if there are any known issues. I certainly don't see anything in your code that could cause it to go around the code multiple times (which is what it looks like it is doing). It almost sounds like (from your example) a flag bit in the uart is not getting cleared properly. I think I better go make coffee ... brain is fuzzy.
mikey _________________ mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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Ttelmah
Joined: 11 Mar 2010 Posts: 19368
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Posted: Sat Nov 24, 2012 12:05 pm |
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I'd say, either the watchdog is getting enabled, and the chip is therefore restarting, or you have a glitch on the power supply, and the chip is doing a brownout restart. Either would explain what you are seeing.
The brownout in particular, does have a wide range in the data sheet. If I remember correctly BORV42, can actually trigger as high as 4.7v on some chips. I had a batch a while ago, that triggered well above the rated figure....
Best Wishes |
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small_chick
Joined: 17 Jul 2012 Posts: 53
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Posted: Sat Nov 24, 2012 7:12 pm |
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Ttelmah wrote: | I'd say, either the watchdog is getting enabled, and the chip is therefore restarting, or you have a glitch on the power supply, and the chip is doing a brownout restart. Either would explain what you are seeing.
The brownout in particular, does have a wide range in the data sheet. If I remember correctly BORV42, can actually trigger as high as 4.7v on some chips. I had a batch a while ago, that triggered well above the rated figure....
Best Wishes |
I have disabled WatchDog => it can't work !
Maybe you're right about Brownout mode!
Now, it works better, I have had some changes:
1/-add a delay about 20(ms) at first in void main().
2/-config line at the top as follows:
Code: | #fuses XT_PLL4,NOWDT,PUT64,BORV27,NOBROWNOUT |
![Very Happy](images/smiles/icon_biggrin.gif) |
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Ttelmah
Joined: 11 Mar 2010 Posts: 19368
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Posted: Sun Nov 25, 2012 1:48 am |
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Just because it is disabled in the code you post, doesn't mean it is disabled in the chip. Depending on what programmer you are using, the fuse might not be being erased, or might be being set by a 'setup' option somewhere. The only way to be 'sure' is to read the fuses back from the chip, and verify the corresponding bit.
I really would suspect you have got spikes on your power rail though. The processor _must_ have decoupling with really good high frequency behaviour (this means something like ceramic, or polyester capacitors, _not_ electrolytic), right close to the chip. I'd be suspicious you are actually getting tiny spikes as things happen...
Best Wishes |
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