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KU5D
Joined: 10 Feb 2008
Posts: 46
Location: Asheville, North Carolina
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| Port E problem? 18F4525 |
 Posted: Mon May 12, 2008 9:11 am |
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Guys,
This seems strange to me, or I'm missing something simple. I have a device that among many other things uses onewire to read an iButton. Initially, I was using pin_C4 as the one-wire pin, and the thing worked flawlessly. However, due to other hardware considerations I moved from C4 to E2, which is of course one of the analog input pins. I'm wondering if I have to specifically set the direction for this pin when writing to and reading from the one wire. On the C port, I didn't have to do this.
Now, along with the onewire, I have 7 analog inputs that I need to read, so here's how I set up my analog inputs:
| Code: |
#define ADC_CLOCK_INTERNAL 0X07
#define AN0_TO_AN6 0x08
//initialize adc input channel and set up ports
inputChannel = 0;
setup_adc_ports (AN0_TO_AN6); //set AN0 thru AN6 analog
setup_adc (ADC_CLOCK_INTERNAL);
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This should exclude E2 and I think it should be now a digital input.
This is what the .lst file shows:
| Code: |
.................... setup_adc_ports (AN0_TO_AN6); //set AN0 thru AN6 analog
7D04: MOVF FC1,W
7D06: ANDLW C0
7D08: IORLW 08
7D0A: MOVWF FC1
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I'm wondering two things. 1. is the compiler setting this up correctly, or 2. do I have to explicitly set the data direction on port E when using it as an input or output?
Ah yes, my compiler version is 3.249.
_________________
Confidence is the feeling you have right before you fully understand the situation... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon May 12, 2008 10:21 am |
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Are you using standard i/o mode (the default mode), and are you
using CCS pin i/o functions ?
If so, the compiler should set the correct TRIS automatically. |
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KU5D
Joined: 10 Feb 2008
Posts: 46
Location: Asheville, North Carolina
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| Posted: Mon May 12, 2008 10:29 am |
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Can I do that and still use analog ins 0 thru 6, and have what was AN7 (pin E2) as a digital I/O for the onewire? Right now, I am not doing #USE STANDARD IO. I am using standard CCS pin funtions such as output_bit...
_________________
Confidence is the feeling you have right before you fully understand the situation... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon May 12, 2008 10:53 am |
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It's the default mode. You don't have to specify it. It's automatically
in effect unless you override it by using #use fast_io or #use fixed_io.
In the test program shown below, the following code is generated for
the output_bit() function. It does set the TRIS. So I think your problem
is somewhere else. I don't think it's the TRIS, unless you're doing
something else besides using output_bit().
| Code: |
... output_bit(PIN_E2, 1);
0014: BSF LATE.2
0016: BCF TRISE.2
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| Code: |
#include <18F452.h>
#fuses XT,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4000000)
//=================================
void main()
{
output_bit(PIN_E2, 1);
while(1);
} |
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KU5D
Joined: 10 Feb 2008
Posts: 46
Location: Asheville, North Carolina
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| Posted: Mon May 12, 2008 11:14 am |
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OK, the output seems to be working, at least it doesn't look any different on a 'scope than it does on Port C. However, this is a onewire device that I read, so I suspect that once I send the command from Pin_E2, I need to turn it around and make it an input. Can I do this by pin, or do I have to set the direction for the entire port? I still need to keep my analog inputs AN0 thru AN6.
I didn't include #fuses in the previous post. Here they are (don't think this is the issue):
| Code: |
#device ADC=8
#device HIGH_INTS=TRUE
#fuses HS,NOWDT,NOPROTECT,NOLVP,PUT
#use delay(clock=10000000)
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_________________
Confidence is the feeling you have right before you fully understand the situation... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon May 12, 2008 11:17 am |
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The CCS pin i/o function that changes a pin to an input is the
output_float() function. Here is the code from the test program
shown below:
| Code: |
... output_bit(PIN_E2, 1);
0014: BSF LATE.2
0016: BCF TRISE.2
...
... output_float(PIN_E2);
0018: BSF TRISE.2
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| Code: | #include <18F452.h>
#fuses XT,NOWDT,PUT,BROWNOUT,NOLVP
#use delay(clock=4000000)
//=================================
void main()
{
output_bit(PIN_E2, 1);
output_float(PIN_E2);
while(1);
} |
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KU5D
Joined: 10 Feb 2008
Posts: 46
Location: Asheville, North Carolina
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| Posted: Mon May 12, 2008 11:24 am |
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OK, here's my onewire code. There's a function at the bottom that is called from main() when a timer runs out and sets the getOneWire flag. It's called "DoOnewire". As I said earlier, this works fine if I define the OneWire as pin C4. It breaks if I use E2. The array called AnalogIns[] may be a bit misleading...it isn't the ADC, it's a buffer used to ship this stuff over a radio link.
| Code: |
void onewire_reset() // OK if just using a single permanently connected device
{
output_low (OneWire); // pull 1-wire low for reset pulse
delay_us(500);
output_float(OneWire); // float 1-wire high
delay_us(500);
output_float(OneWire);
}
//================== onewire_write() =========================
void onewire_write(int data)
{
int count;
for (count=0; count<8; ++count)
{
output_low(OneWire);
delay_us( 2 ); // pull 1-wire low to initiate write time-slot.
output_bit(OneWire, shift_right(&data,1,0)); // set output bit on 1-wire
delay_us(60);
output_float(OneWire); // set 1-wire high again,
delay_us( 2 ); // for more than 1us minimum.
}
}
//====================== read1wire() ===================================
//This function reads the 8 -bit data via the 1-wire sensor. */
//
//Parameters:
//Returns: 8-bit (1-byte) data from sensor
//======================================================================
int8 onewire_read()
{
int8 count, data;
for (count=0; count<8; ++count)
{
output_low(OneWire);
delay_us( 2 ); // pull 1-wire low to initiate read time-slot.
output_float(OneWire); // now let 1-wire float high,
delay_us( 8 ); // let device state stabilise,
shift_right(&data,1,input(OneWire)); // and load result.
delay_us(120);
}
return( data );
}
//==============================================================================
// DoOneWire()
DoOneWire()
{
int8 oneWireCnt;
int8 busy = 0;
disable_interrupts(GLOBAL);
onewire_reset();
onewire_write(0x33);
while (busy == 0)
busy = onewire_read();
onewire_reset();
onewire_write(0x33);
for(oneWireCnt = 8; oneWireCnt >0; oneWireCnt--)
{
AnalogIns[oneWireCnt + 7] = onewire_read();
}
getOneWire = FALSE; //clear the get me flag
if(inDebugMode)
{
fprintf(PC,"iButton: %X %X %X %X %X %X %X %X \r",AnalogIns[8],AnalogIns[9],AnalogIns[10],AnalogIns[11],
AnalogIns[12],AnalogIns[13],AnalogIns[14],AnalogIns[15]);
}
enable_interrupts(GLOBAL);
}
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_________________
Confidence is the feeling you have right before you fully understand the situation... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon May 12, 2008 11:46 am |
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Do you know for sure that Pin E2 is free ? What if it's connected to a
pull-down resistor or some other circuit ?
I suggest trying a different pin than E2. See if another pin will work. |
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KU5D
Joined: 10 Feb 2008
Posts: 46
Location: Asheville, North Carolina
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| Posted: Mon May 12, 2008 12:23 pm |
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PCM,
Try this on for infuriating:
2 identical iButton sockets; 1 wired for the old board using C4 and the other wired for the new board using E2. All made up nice and neat with heatshrink, and good connectors.
Problem: ground wire separated inside of heatshrink on socket for new board. I've chased this for hours and wasted not only my time, but yours as well.
My apologies,
many thanx
_________________
Confidence is the feeling you have right before you fully understand the situation... |
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