| Author |
Message |
Guest
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 Posted:
Fri Dec 17, 2004 1:57 am Post subject:
pic16f77 acting goofy |
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I will try to make this question as short as possible. I'm making a
"quiz box" that displays the first two of any 20 players that buzz in.
I'm using a pic16f77. The program scans 20 ports (buttons) and
displays the first two numbers (1-20) on four single digit 7-segment
LED displays via a display driver. Also, a speaker buzzes after the
first player has buzzed in. Everything works great except for this one
"little" bug.
When I first turn on the power, the displays get set to zero's and the
program starts scanning the buttons. If I first push a button in the
teens (10-19) the first digit is always wrong. For example, in stead
of displaying 12, it displays 32 or 72. Next I push a button (1-9) and
it displays correctly. If I reset the program and push the same
buttons in the same order, the problem occurs again. However, if I
reset the program and first push a button (1-9), then push a button
(10-20), it displays correctly and every time thereafter until the
power switch is toggled off then on again.
The same thing happens when I turn the power on and first press a
button (1-9) then a button (10-19) - it displays incorrectly until I
reverse the order. I push one (10-19) then one (1-9) and everything
works fine.
So, everytime I want to use it, I have to "intialize" it to get past
the bug before it will work right. This problem is very perplexing.
The program debugs fine. There is absolutely no reason for the mc to
be spitting out these goofy numbers. Does anyone have any idea,
hardware or software, what could be causing this problem? I hope this
wasn't too confusing. Thanks in advance.
Steve |
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Ulf Samuelsson
Guest
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| Posted:
Fri Dec 17, 2004 3:03 am Post subject:
Re: pic16f77 acting goofy |
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| Quote: | So, everytime I want to use it, I have to "intialize" it to get past
the bug before it will work right. This problem is very perplexing.
The program debugs fine. There is absolutely no reason for the mc to
be spitting out these goofy numbers. Does anyone have any idea,
hardware or software, what could be causing this problem? I hope this
wasn't too confusing. Thanks in advance.
|
This problem is best fixed by single stepping in an emulator or in a
simulator.
I would be surprised if it was not a S/W problem.
--
Best Regards,
Ulf Samuelsson ulf@a-t-m-e-l.com
This is a personal view which may or may not be
share by my Employer Atmel Nordic AB |
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Noel Henson
Guest
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| Posted:
Fri Dec 17, 2004 3:10 am Post subject:
Re: pic16f77 acting goofy |
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mcki0127@hotmail.com wrote:
| Quote: | I will try to make this question as short as possible. I'm making a
"quiz box" that displays the first two of any 20 players that buzz in.
I'm using a pic16f77. The program scans 20 ports (buttons) and
displays the first two numbers (1-20) on four single digit 7-segment
LED displays via a display driver. Also, a speaker buzzes after the
first player has buzzed in. Everything works great except for this one
"little" bug.
When I first turn on the power, the displays get set to zero's and the
program starts scanning the buttons. If I first push a button in the
teens (10-19) the first digit is always wrong. For example, in stead
of displaying 12, it displays 32 or 72. Next I push a button (1-9) and
it displays correctly. If I reset the program and push the same
buttons in the same order, the problem occurs again. However, if I
reset the program and first push a button (1-9), then push a button
(10-20), it displays correctly and every time thereafter until the
power switch is toggled off then on again.
The same thing happens when I turn the power on and first press a
button (1-9) then a button (10-19) - it displays incorrectly until I
reverse the order. I push one (10-19) then one (1-9) and everything
works fine.
So, everytime I want to use it, I have to "intialize" it to get past
the bug before it will work right. This problem is very perplexing.
The program debugs fine. There is absolutely no reason for the mc to
be spitting out these goofy numbers. Does anyone have any idea,
hardware or software, what could be causing this problem? I hope this
wasn't too confusing. Thanks in advance.
Steve
|
It sounds like you have forgotten to initialize a register. Namely, the one
that holds the most-significant digit. Check your initialization code.
Noel |
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Jim Granville
Guest
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| Posted:
Fri Dec 17, 2004 4:12 am Post subject:
Re: pic16f77 acting goofy |
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mcki0127@hotmail.com wrote:
<snip>
| Quote: |
When I first turn on the power, the displays get set to zero's and the
program starts scanning the buttons. If I first push a button in the
teens (10-19) the first digit is always wrong. For example, in stead
of displaying 12, it displays 32 or 72. Next I push a button (1-9) and
it displays correctly. If I reset the program and push the same
buttons in the same order, the problem occurs again. However, if I
reset the program and first push a button (1-9), then push a button
(10-20), it displays correctly and every time thereafter until the
power switch is toggled off then on again.
The same thing happens when I turn the power on and first press a
button (1-9) then a button (10-19) - it displays incorrectly until I
reverse the order. I push one (10-19) then one (1-9) and everything
works fine.
So, everytime I want to use it, I have to "intialize" it to get past
the bug before it will work right. This problem is very perplexing.
The program debugs fine.
|
?!
| Quote: | There is absolutely no reason for the mc to
be spitting out these goofy numbers.
|
Well, there clearly must be a reason - it sounds very predictable:
you have just not found the reason, yet.
| Quote: | Does anyone have any idea,
hardware or software, what could be causing this problem?
|
You have enough info in the interaction to start the debug process.
When a system is path dependent, but does have the ability to behave
correctly, it points to a software initialise problem.
Look for different variable handling, in your 'works OK' path, from
the 'fails' path.
It is good practice to clear all variable RAM on reset, in a 80c51
this takes 6 bytes of code - and can save a lot of other variable inits.
You then code, so all 'safe defaults' are the 00 or FALSE values.
-jg |
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Jonathan Kirwan
Guest
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| Posted:
Fri Dec 17, 2004 4:31 am Post subject:
Re: pic16f77 acting goofy |
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I did something similar with an Atmel AT90S2313 processor. Code works fine and
is in use, I believe. Circuit schematics and box and source code etc. are all
right here if that helps, too. Here's some of the header comments:
; This program operates a Jeopardy or college-bowl kind of game device
; where the first person to press a switch is selected, locking out the
; others. Eight contestants are supported, each by direct connection to
; an input pin. An LED lights up to indicate which switch (contestant)
; is pressed first and the rest of the contestants are then locked out.
; The buzzer emits a short burst, as well, to signal that a contestant
; has pressed their button.
Not 20 buttons in this case, but extending it would be easy. In any case, the
basic ideas in the code are there, too.
Jon |
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Nicholas O. Lindan
Guest
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| Posted:
Fri Dec 17, 2004 4:42 am Post subject:
Re: pic16f77 acting goofy |
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"Jim Granville" <no.spam@designtools.co.nz> wrote
| Quote: | When a system is path dependent, but does have the ability to behave
correctly, it points to a software initialise problem.
It is good practice to clear all variable RAM on reset
|
Zeroing ram is always a good idea at the start, but I find
it most useful in debugging because it makes a memory dump
easier to interpret.
I develop with RAM zeroed, and then verify operation with
ram set to 0FFH. Variables that are not explicitly initialized
are verboten under all circumstances.
If you are having weird problems then setting memory to all 1's can
often make the source of the problem stand out like a sore thumb (or
stamp).
--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ |
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Guest
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| Posted:
Fri Dec 17, 2004 9:34 pm Post subject:
Re: pic16f77 acting goofy |
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Wow, thanks for all the help and suggestions. I'm using MPLAB IDE
v6.61 with MPLAB SIM. I can step through the program and use the pin
stimulus feature to check the different scenarios. The program seems
to work fine, storing all the correct values in each register.
I've declared two variables that keep track of the buttons pushed:
flag1 and flag2. I intitialize these registers by
clrf flag1
clrf flag2
Is this sufficient? In a later subroutine, those hex numbers get split
into dig1a, dig1b, dig2a, and dig2b to be sent to the display driver.
They are initialized the same way. I'm not exactly sure what is meant
by the RAM. Is that the block of general purpose registers used to
store all the variables? If that's the case, then mine starts at 020H.
If I write all 0's (or 1's) to these registers, should I then run the
program to the point where it's messing up, and then do a memory dump
to see what each variable holds?
Jon, I would like to take a look at your box design, but there doesn't
seem to be a link with your message :=)
Steve |
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Noel Henson
Guest
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| Posted:
Fri Dec 17, 2004 10:03 pm Post subject:
Re: pic16f77 acting goofy |
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mcki0127@hotmail.com wrote:
| Quote: | Wow, thanks for all the help and suggestions. I'm using MPLAB IDE
v6.61 with MPLAB SIM. I can step through the program and use the pin
stimulus feature to check the different scenarios. The program seems
to work fine, storing all the correct values in each register.
I've declared two variables that keep track of the buttons pushed:
flag1 and flag2. I intitialize these registers by
clrf flag1
clrf flag2
Is this sufficient? In a later subroutine, those hex numbers get split
into dig1a, dig1b, dig2a, and dig2b to be sent to the display driver.
They are initialized the same way. I'm not exactly sure what is meant
by the RAM. Is that the block of general purpose registers used to
store all the variables? If that's the case, then mine starts at 020H.
If I write all 0's (or 1's) to these registers, should I then run the
program to the point where it's messing up, and then do a memory dump
to see what each variable holds?
Jon, I would like to take a look at your box design, but there doesn't
seem to be a link with your message :=)
Steve
|
During your initialization, did you setup your PORTs to have the correct
default value? This is usually done just before a write to TRIS. It is just
as important as properly initializing your variables.
Noel |
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Guest
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| Posted:
Fri Dec 17, 2004 10:33 pm Post subject:
Re: pic16f77 acting goofy |
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Yes, I also clear all the ports before writing to the TRIS registers.
Steve |
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Spehro Pefhany
Guest
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| Posted:
Fri Dec 17, 2004 10:41 pm Post subject:
Re: pic16f77 acting goofy |
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On 17 Dec 2004 09:33:19 -0800, the renowned mcki0127@hotmail.com
wrote:
| Quote: | Yes, I also clear all the ports before writing to the TRIS registers.
Steve
|
Assuming your program is written in assembler, this sounds like the
kind of PIC bug that results from forgetting a bank select instruction
somewhere.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com |
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Noel Henson
Guest
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| Posted:
Fri Dec 17, 2004 10:43 pm Post subject:
Re: pic16f77 acting goofy |
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mcki0127@hotmail.com wrote:
| Quote: | Yes, I also clear all the ports before writing to the TRIS registers.
Steve
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Steve,
I'm not trying to second-guess you but, is clearing the ports the correct
thing to do? In my own circuits, I usually have low-true scan signals. When
I do, I set those port bits to a 1.
HTH,
Noel |
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Guest
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| Posted:
Fri Dec 17, 2004 11:13 pm Post subject:
Re: pic16f77 acting goofy |
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My program is written in assembler and I've tried to be careful about
writing to the correct banks. I do however get several messages like
this one:
Message[302] C:\PIC PROJECTS\QUIZ.ASM 34 : Register in operand not in
bank 0. Ensure that bank bits are correct.
This is referring to me writing to the OPTION_REG which is in bank1.
bank1
movlw b'10000111'
movwf OPTION_REG ; intitialize interrupts
bank1 macro
bsf STATUS, RP0
bcf STATUS, RP1
endm
So, I think I'm writing to the banks correctly. |
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Guest
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| Posted:
Fri Dec 17, 2004 11:16 pm Post subject:
Re: pic16f77 acting goofy |
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Noel,
Do you mean that your inputs are active low? Mine are active high. I
have 1K pull-down resistors from each pin to ground.
Steve |
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Spehro Pefhany
Guest
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| Posted:
Fri Dec 17, 2004 11:28 pm Post subject:
Re: pic16f77 acting goofy |
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On 17 Dec 2004 10:13:14 -0800, the renowned mcki0127@hotmail.com
wrote:
| Quote: | My program is written in assembler and I've tried to be careful about
writing to the correct banks. I do however get several messages like
this one:
Message[302] C:\PIC PROJECTS\QUIZ.ASM 34 : Register in operand not in
bank 0. Ensure that bank bits are correct.
This is referring to me writing to the OPTION_REG which is in bank1.
bank1
movlw b'10000111'
movwf OPTION_REG ; intitialize interrupts
bank1 macro
bsf STATUS, RP0
bcf STATUS, RP1
endm
So, I think I'm writing to the banks correctly.
|
And you switch back to bank 0 after that in every case?
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com |
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Guest
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| Posted:
Fri Dec 17, 2004 11:35 pm Post subject:
Re: pic16f77 acting goofy |
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Yes I do, and I just stepped through the program again while monitoring
the STATUS bits. After initializations, the bank bits stay in bank0
for the remainder of the program. |
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