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Jason Guest
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fail to connect through I2C |
Posted: Mon May 08, 2006 5:08 am |
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The program was programmed to send a data to the the slave processor. but the slave program started the I2C interrupt but failed to read the data from mater mode and stay on the command "I2C_Data_Rx=i2c_read(0);".
here are the master and slave code
MASTER CODE
_____________________________________________________________
#include <16F877.H>
#fuses HS,NOWDT,NOPUT,NOBROWNOUT,NOLVP,NOPROTECT
#use delay(clock=20000000)
#use I2C(master,sda=PIN_C4,scl=PIN_C3,FORCE_HW)
#define SCL PIN_C3
#define SDA PIN_C4
char I2C_Data_Tx;
void main()
{
output_float(SCL);
output_float(SDA);
I2C_Data_Tx = 0x01;
while(1)
{
i2c_start();
delay_us(50);
i2c_write(0xA1);
delay_us(50);
i2c_write(I2C_Data_Tx);
delay_us(50);
i2c_stop();
}
}
SLAVE CODE
_____________________________________________________________
#include <16F877.H>
#fuses HS,NOWDT,NOPUT,NOBROWNOUT,NOLVP,NOPROTECT
#use delay(clock=20000000)
#use I2C(slave,sda=PIN_C4,scl=PIN_C3,address = 0xA1,FORCE_HW)
#define SCL PIN_C3
#define SDA PIN_C4
char I2C_Data_Rx;
#INT_SSP
void I2C_Recieve()
{
output_b(0x00);
while(!i2c_poll())
I2C_Data_Rx=i2c_read(0);
}
void main()
{
output_float(SCL);
output_float(SDA);
enable_interrupts(GLOBAL);
enable_interrupts(INT_SSP);
I2C_Data_Rx = 0x00;
output_b(0xff);
while(1)
{
if(I2C_Data_Rx != 0x00)
{
Output_b(I2C_Data_Rx);
I2C_Data_Rx = 0x00;
}
}
}
Please help me finding out what is the error on it?
I have already connect the pins with 10kohm pull-up resistor |
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Ttelmah Guest
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Posted: Mon May 08, 2006 6:31 am |
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There are quite a few problems. Do a search on the group, some working I2C routines have been published here in the past. However as a quick overview just of the problems in the interrupt routine:
1) You are reading a character when I2c_poll is false. It will _always_ be true when the interrupt occurs. When false, it means there is not a character waiting. If true, you do not read the byte, which then doesn't reset the I2C interrupt.
2) You have an address of '0xA1'. This is not a legitimate I2C address. I2C addresses occupy only the top seven bits of the address byte. Having a '1' in the low bit, implies the I2C transaction, is a read. You then try to write data...
3) You try to use I2C_read(NACK) for all bytes. Look at where ACK should be sent, and not sent.
4) Your receive routine, needs to distiguish what state the I2C bus is in. look at I2C_ISR_STATE...
There is a basic I2C slave example, in the CCS example files included wth the compiler.
Best Wishes |
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Jason Guest
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Posted: Tue May 09, 2006 3:21 am |
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thank you.
but the program still running i2c_read() continuously.
I have checked the assembly list, it is waiting for the 7 bit address..
isn't that there are some problem in my master code? |
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