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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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 Posted: Thu Mar 15, 2007 12:56 pm |
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Now that I look at it, I can say that the CCS Ex_slave.c example
has no ability to receive or send more than one data byte per
i2c operation. If you look at the #int_ssp isr code, you can see
that there is no code to ever increment the 'address' variable.
So despite the comments in that file, it doesn't really completely
emulate the 24LC01 eeprom. You can't do sequential reads or
writes of more than 1 byte.
So your code will have be modified. |
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bestbuylvr
Joined: 31 Jan 2007
Posts: 27
Location: Pittsburgh, PA
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| Posted: Thu Mar 15, 2007 1:19 pm |
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OK, here is the story. I skimmed this down to next to nothing, and it still doesnt work when trying to send multiple bits. When I comment out the sections making the program send more than one byte, it works properly. Once I add the multiple byte section, the program freezes. I placed a printf after the write section, with the multiple byte writing, and it gets that far. Once the program gets to the reading multiple bytes, it holds up. I will post the program with the commented out sections. This version works to transmit one byte, but once you take the comments out and change the first i2c_read(0) to i2c_read(), the program freezes. Here is the code, it may help to copy and paste it into a compiler program to visualize the comments with color. Thank you.
| Code: | #include <18F452.h>
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use i2c(Master, SDA=PIN_C4, SCL=PIN_C3)
//====================================
void main()
{
int8 f0, f1, f2, f3, g0, g1, g2, g3;
f0=1;
f1=2;
f2=3;
f3=4;
while(1){
// Write float to the slave 1 board.
i2c_start();
i2c_write(0xA0);
i2c_write(0x00);
i2c_write(f0);
/*i2c_write(0x01);
i2c_write(f1);
i2c_write(0x02);
i2c_write(f2);
i2c_write(0x03);
i2c_write(f3);
i2c_stop();
delay_ms(200);
printf("Written.\n\r");*/
// Read float bytes from the slave 1 board and display the data.
i2c_start();
i2c_write(0xA0);
i2c_write(0x00);
i2c_start();
i2c_write(0xA1);
g0 = i2c_read(0);
/*g1 = i2c_read();
g2 = i2c_read();
g3 = i2c_read(0); */
i2c_stop();
printf("read from 1: %d \n\r", g0);
//printf("read from 1: %d %d %d %d \n\r", g0, g1, g2, g3);
delay_ms (200);
}
}
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bestbuylvr
Joined: 31 Jan 2007
Posts: 27
Location: Pittsburgh, PA
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| Posted: Thu Mar 15, 2007 1:22 pm |
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| Sorry, I missed your last post. It appears that this has become even more complicated... I'll re-examine this to see if it is worth the re-writing of the EX_SLAVE.c program. If you have any easy modifications for that, pleease post. If it is too complicated, don't waste your time, at least not yet. I thank you for your help, it would have taken me a lot longer to discover that. I am glad you take the time to help people like me out, I do appreciate it. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 15, 2007 1:28 pm |
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Try doing it with four totally separate write sequences, each writing
only one byte, and each with it's own i2c start and stop statements.
Do the same thing for read. |
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bestbuylvr
Joined: 31 Jan 2007
Posts: 27
Location: Pittsburgh, PA
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| Posted: Mon Mar 19, 2007 7:28 am |
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| I tried the separate write sequence idea, but the program just seems to freeze up every time after the write process. Does anyone know of an existing I2C Slave program capable of writing and reading to and from different address locations? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Mar 19, 2007 3:04 pm |
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I made a test program for the i2c Master PIC, and it works OK.
It can successfully write and read four floating point numbers to
a PIC which is running the CCS Ex_Slave.c program.
Here is the output from the program below, as displayed on
a terminal window on my PC:
| Quote: |
addr = 0, value = 1.234560
addr = 4, value = 4.567890
addr = 8, value = 3.141590
addr = 12, value = 2.718280
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Put this program into the Master PIC. Connect it to another
PIC which is running Ex_Slave.c. Be sure to use pull-up resistors
on the SDA and SCL lines. Also connect a ground wire between
the two boards.
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
// Use the CCS driver for a 24LC01 eeprom to provide the
// low level i2c read and write routines which will talk
// to the PIC that is running the Ex_Slave.c program.
#include <2401.c>
// The following two routines come from the CCS FAQ page:
http://www.ccsinfo.com/faq.php?page=write_eeprom_not_byte
//---------------------------------------------------
void write_float_to_ext_eeprom(long int n, float data)
{
int i;
for(i = 0; i < 4; i++)
write_ext_eeprom(i + n, *((int8*)&data + i) ) ;
}
//------------------------------------
float read_float_ext_eeprom(long int n)
{
int i;
float data;
for(i = 0; i < 4; i++)
*((int8*)&data + i) = read_ext_eeprom(i + n);
return(data);
}
//===============================
void main()
{
int8 i;
float value;
float result;
int8 addr;
// Write four floating point numbers
// to the "eeprom" in a PIC that is
// running the Ex_Slave.c program.
// Each floating point number will take
// four bytes in the "eeprom", so the
// address must be advanced by 4 for
// each new value that is written to
// "eeprom". Also, the Ex_Slave.c
// program only has a 16-byte array
// to store the data. So only four
// floats can be written to it.
value = 1.23456;
write_float_to_ext_eeprom(0, value);
value = 4.56789;
write_float_to_ext_eeprom(4, value);
value = 3.14159;
write_float_to_ext_eeprom(8, value);
value = 2.71828;
write_float_to_ext_eeprom(12, value);
// Now read the floating point numbers
// from the Ex_Slave PIC and display them.
addr = 0;
for(i = 0; i < 4; i++)
{
result = read_float_ext_eeprom(addr);
printf("addr = %lu, value = %f \n\r" , addr, result);
addr += 4;
}
while(1);
} |
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