Posted on May 26, 2006 at 06:13Hello Dvir,
You are configuring the I2C in Fast mode(FM/SM =1). The SCL frequency = 64Mhz /(3x CC(11:0) + 9) & CC(11:0) = 0xF0
So, SCL frequency = 88Khz which doesn't correspond to Fast mode(< 100 Khz).
So, the CCR1 and CCR2 registers values should be changed.
There are somethings missing in your code:
- The ACK bit must be set in the CR register (Enable Acknowledge).
- After sending the START condition, a wait until the SB bit is set in I2CSR1 register is necessary. Then, this bit should be reset by software.
- Normally, the first write in DR register corresponds to the slave address sent by the Master. After this write, a wait until ENDAD bit is set in I2CSR2 register is also necessary. Then, this bit should be reset by software.
The status bits (in SR1 and SR2 registers) are set by hardware and reset by software. For more details, please refer to the Transfer Squencing and different events, in the ST10F276 user's manual(pages 370, 371).
Let's take an example:
----------------------
You want to write the data 0x10 in the address 0x00 of an I2C 8 bit eeprom. The eeprom address is 0xA0.
Fcpu = 64Mhz & SCL frequency = 50Khz (Standard mode).
#define I2C_PE ((unsigned char)0x20)
#define I2C_START ((unsigned char)0x08)
#define I2C_ACK ((unsigned char)0x04)
#define I2C_STOP ((unsigned char)0x02)
#define I2C_ITE ((unsigned char)0x01)
#define I2C_BTF ((unsigned char)0x08)
#define I2C_SB ((unsigned char)0x01)
#define I2C_ENDAD ((unsigned char)0x20)
void routine_I2C(void)
{
OAR2 = 0xA0;
CR |= I2C_PE;
CR |= I2C_PE;
CR |= I2C_ACK;
/* So for 50KHz at 64MHz */
CCR1 = 0x7C;
CCR2 = 0x04;
/* The master generates the START condition*/
CR |= I2C_START;
/* Check if START condition is generated */
while (!(SR1 & I2C_SB));
Temp = SR1; /* Clear SB bit */
/* The master sends the eeprom address */
DR = 0xA0;
/* The address transmission check is done with a pooling waiting
loop for the ENDAD flag.*/
while(!(SR2 & I2C_ENDAD));
/* Clear ENDAD bit */
Temp = SR2;
CR |= I2C_PE;
/* The master sends the eeprom address of the byte to be written*/
DR = 0x00;
/* Transmission check is done with a polling waiting loop for the BTF
flag of SR1 register.*/
while(!(SR1 & I2C_BTF));
/* The master sends the data byte to be written at 0x00 address */
DR = 0x10;
/* Transmission check is done with a polling waiting loop for the BTF
flag of SR1 register.*/
while(!(SR1 & I2C_BTF));
/* The master generates the STOP condition*/
CR |= I2C_STOP;
}
I hope this helps you.
Please let me know how it goes and if you have further questions.
Best regards,
Najoua.
