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BLL
Joined: 11 Nov 2006 Posts: 181 Location: Birmingham, UK
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18LF4620 port D woes! |
Posted: Fri Jul 15, 2016 12:24 pm |
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Hi,
I am using a 18LF4620 with 10MHz crystal, and H4.
I am trying to use port D2 and D3 as digital inputs.
I have setup_PSP(PSP_DISABLED); at the start of main, as these pins are shown as RD2/PSP2 and RD3/PSP3.
D2 works fine but D3 reads as zero, regardless of the input state.
Can someone explain what I am doing wrong, as the data sheet says that all port D pins can be configured as digital inputs?
Thanks
Brian |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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Posted: Fri Jul 15, 2016 1:44 pm |
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Those are completely ordinary i/o pins. If pin D3 reads at a logic high
level with a scope and the PIC sees it as low, you probably have a
defective PIC. |
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asmboy
Joined: 20 Nov 2007 Posts: 2128 Location: albany ny
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Posted: Fri Jul 15, 2016 2:08 pm |
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if a new PIC does not cure it - you need to show the relevant code you created.
how the pins were inited - and where- how you read them |
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temtronic
Joined: 01 Jul 2010 Posts: 9170 Location: Greensville,Ontario
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Posted: Fri Jul 15, 2016 2:18 pm |
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might also be a short on your PCB, grounding the pin ?
check with power off, no PIC and ring it out
Jay |
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BLL
Joined: 11 Nov 2006 Posts: 181 Location: Birmingham, UK
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Posted: Fri Jul 15, 2016 2:58 pm |
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Hi all, Thanks for the replies. The PIC is on a prototype board and there is no short. 2 other, brand new PICs behave the same. Each pin has a 10K resistor to +5V and a connector which allows either pin to be grounded by a sensor switch.
All the code does is to check the logic state of each pin:
Code: | sprintf(LCDLine4, "LH Cyl=%u, RH Cyl=%u", input(PIN_D2), input(PIN_D3));
strsetsz(LCDLine4, 20); //pads string to 20 chars with spaces
lcd_gotoxy(1,4);
printf(lcd_putc, LCDLine4); |
Currently, I am using wires for the sensors. A meter proves the pins can be made high (no link) or low (pin grounded)
If I use B7 and B8 instead, all is fine, so a solution is not vital but I am intrigued as to what the problem is.
Brian |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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Posted: Fri Jul 15, 2016 4:11 pm |
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Your code is overly complex for the problem, and your hardware sounds
overly complex as well.
Switch circuit
Code: |
+5v
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<
> 4.7K
< ___ Push button switch
To | _|_|_
PIC -----------------o o------
pin |
D3 --- GND
- |
LED on PIC pin B0
Code: | pin 470 ohms LED
B0 -----/\/\/\/------->|----
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----- Ground
---
- |
Test program:
Code: | #include <18LF4620.h>
#fuses INTRC_IO, NOWDT
#use delay(clock=4M)
//=========================================
void main(void)
{
int8 pin;
while(TRUE)
{
pin = input(PIN_D3); // Read the pin
if(pin)
{
output_high(PIN_B0); // If pin D3 is high, turn on LED
}
else
{
output_low(PIN_B0); // else turn off the LED
}
delay_ms(100);
}
} |
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Ttelmah
Joined: 11 Mar 2010 Posts: 19359
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Posted: Sat Jul 16, 2016 2:39 am |
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Take a deep breath, and start again...
First thing is a simple statement of fact. There is nothing special about these pins, except the PSP.
So first thing to do, is to genuinely 'prove' you do not have a short (it's amazingly easy to have whiskers or tiny solder blobs). Assuming the PIC is socketed, unplug it, and test if the pins now go up/down.
Then assuming they do, you come to the problem being in your code. Look for:
1) Any TRIS statements.
2) Any fast_io/fixed_io statements.
3) Any peripheral setup referring to the pins (could be something silly like a missed line in your LCD code). #USE lines etc..
Always the thing to do, is simplify. As with the test for the lines actually going up/down, reduce code till the problem can be isolated. PCM_Programmer gives a good example of a basic 'test' routine to start from |
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BLL
Joined: 11 Nov 2006 Posts: 181 Location: Birmingham, UK
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Posted: Sat Jul 16, 2016 8:59 am |
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Hi both, thanks for the input.
I eventually traced it to where, just before reading the pins, I had a strcat statement instead of a strcpy to put the first item in a string!!
Putting that right made everything OK.
Thanks for the help.
Brian |
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