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Guest
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| I2C problems / 16f877a / ccs c 3.222 |
 Posted: Thu Jul 28, 2005 4:18 pm |
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the i2c functions does not work at all, with software or hardware interface, the connected pins are powerless, nor 0 or 1.
What to do? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jul 28, 2005 5:17 pm |
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| Quote: | the i2c functions does not work at all, with software or hardware
interface, the connected pins are powerless, nor 0 or 1. |
Not true. I tested the following program with PCM vs. 3.222
with a 16F877A on a PicDem2-Plus board and it worked OK.
Here's the output displayed on my terminal window:
That test was with software i2c. I then edited the 24256.C driver file
to make it use hardware i2c, by changing the #use i2c() statement to:
| Quote: | | #use i2c(master, sda=EEPROM_SDA, scl=EEPROM_SCL, FORCE_HW) |
It worked again. Here is the test program:
| Code: | #include <16F877A.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#include <24256.c>
//=====================================
void main()
{
printf("Start\n\r");
init_ext_eeprom();
write_ext_eeprom(0, 0x55);
write_ext_eeprom(1, 0xAA);
printf("%x ", read_ext_eeprom(0));
printf("%x", read_ext_eeprom(1));
while(1);
} |
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Ttelmah
Guest
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| Posted: Fri Jul 29, 2005 4:11 am |
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One obvious commet applies. The poster is presumably aware that the I2C pins are driven to emulate open-collector outputs, and a pull-up resistor is needed on each line?. The pins will default to the 'undriven' state, with the lines floating.
Best Wishes |
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Guest
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| Posted: Fri Jul 29, 2005 1:26 pm |
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i know about the resistors ... however, i got some bit banging routines
and now its working without the i2c support in ccs.
thanks anyway. |
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MikeValencia
Joined: 04 Aug 2004
Posts: 238
Location: Chicago
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| Posted: Fri Jul 29, 2005 2:26 pm |
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I addressed this question before in:
http://www.ccsinfo.com/forum/viewtopic.php?t=23221&highlight=i2cstart+bug
Try upgrading to 3.223
I don't know why it works with some people and not with others.
I asked CCS what is was the bug in before 3.223, since I did experience occasional i2c_write() errors following an i2c_start().
I never got a response, so i figured i'd write my own MSSP-based master routines.
Maybe i should try the latest version and see if my previous problem disappears. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Jul 29, 2005 2:50 pm |
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CCS admits there was a problem with i2c -- I assume in vs. 3.222.
From their versions page:
| Quote: | | 3.223 A problem with I2C_START() on some parts is fixed |
They didn't say what PICs are affected, so that's why I tested his PIC,
a 16F877A, in hardware, with both software and H/W i2c.
He didn't give his application circuit, but I suspect that he may have
been using the CCS eeprom driver. It defaults to using pins B1 and B0.
If you want to use the hardware pins (for most 40-pin chips), you have
to place the new pin definition statements above the #include line for
the driver, like this:
| Code: | #define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#include <24256.c> |
If you don't do that, the i2c will come out the wrong pins and give
the impression that "i2c doesn't work".
I didn't mention this because he was adament that it "didn't work",
and if that's how he feels, then I'm not going to push it. |
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sseidman
Joined: 14 Mar 2005
Posts: 159
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| Posted: Fri Jul 29, 2005 3:51 pm |
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| PCM programmer wrote: | above the #include line for
the driver, like this:
| Code: | #define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#include <24256.c> |
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That's one of the niftiest tips I've seen yet!! I just edit the driver for the pins I'm using, but daisy-chaining the defines is about five times as elegant.
Scott |
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