Read pressure sensor with I2C in master receiver mode

[philipgillespie]

Posted on June 08, 2011 at 10:12

Hi All,

Need some advise here with I2C.  I'm trying to use I2C in master receiver mode to read two bytes of data out of a pressure sensor.  The required command sequence is pg 8 of attached data sheet. Here is the code:        GPIO_InitTypeDef  GPIO_InitStructure;        /* SDA */       GPIO_InitStructure.GPIO_Pin =     GPIO_Pin_7;       GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;       GPIO_InitStructure.GPIO_Mode =   GPIO_Mode_AF_OD;       GPIO_Init(GPIOB, &GPIO_InitStructure);       GPIO_InitStructure.GPIO_Pin       =   GPIO_Pin_6;       GPIO_InitStructure.GPIO_Speed   =  GPIO_Speed_50MHz;                 GPIO_InitStructure.GPIO_Mode    =  GPIO_Mode_AF_OD;                     GPIO_Init(GPIOB, &GPIO_InitStructure);        I2C_InitTypeDef  I2C_InitStructure;      /* I2C configuration */      I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;      I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;      I2C_InitStructure.I2C_OwnAddress1 = I2C1_SLAVE_ADDRESS7;      I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;      I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;      I2C_InitStructure.I2C_ClockSpeed = I2C_Speed;      I2C_Cmd(I2C1, ENABLE);      I2C_Init(I2C1, &I2C_InitStructure);         int sensor_data[2];         sensor_data[0] = 0x00;         sensor_data[1] = 0x00;         /* Enable I2C1 acknowledgement if it is already disabled by other function */         I2C_AcknowledgeConfig(I2C1, ENABLE);         /* While the bus is busy */         while(I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY));         /*----- Transmission Phase -----*/         /* Send START condition */         I2C_GenerateSTART(I2C1, ENABLE);         /* Test on EV5 and clear it */         while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));                                 /* Send sensor address */         I2C_SendData(I2C1,0xF1);                /* Test on EV6 and clear it */         while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED));                                  /* Read a byte from the sensor*/           sensor_data[0] = I2C_ReceiveData(I2C1);                 /* Test on EV7 and clear it */         while(I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_RECEIVED));                 sensor_data[1] = I2C_ReceiveData(I2C1);                 /* Test on EV7 and clear it */         while(I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_RECEIVED));                     /* Send I2C1 STOP Condition */         I2C_GenerateSTOP(I2C1, ENABLE); After i send out the address of the sensor, i'm seeing (on the scope) two byte of data with 18 clock cycles.  I assumed this data is only read out using I2C_ReceiveData? Also is a NACK command required before stop commmand? Any suggestions about what I'm not doing correctly would be greatly appreciated. -- Thanks   #embedded-c