STM8S_010_I2C read and write EEPROM (hardware method)

Ⅰ. Write in front

I believe that those who have read the previous article "A Deeper Understanding of I2C Bus, Protocol and Application" have a certain understanding of I2C. That article is about I2C, using microcontroller IO to simulate I2C to achieve read and write operations.

This article will describe the hardware I2C read and write operations, that is, the clock and data transmission process implemented by the processor's own hardware I2C.

Ⅱ. STM8 Hardware I2C Knowledge

The I2C module of STM8S can not only receive and send data, but also convert data from serial to parallel data when receiving and from parallel to serial data when sending. Interrupts can be enabled or disabled. The interface is connected to the I2C bus through the data pin (SDA) and the clock pin (SCL). It allows connection to a standard (up to 100kHz) or fast (up to 400kHz) I2C bus.

1. Four modes of I2C

● Slave device sending mode

● Slave receiving mode

● Master device sending mode

● Master receiving mode

2. Main features of I2C

● Parallel bus/I2C bus protocol converter

● Multi-host function: This module can be used as both a master device and a slave device

● I2C master function

─ Generate start and stop signals

● I2C slave device function

─ Programmable I2C address detection

─ Stop position detection

● Generate and detect 7-bit/10-bit address and general call

● Support different communication speeds

─ Standard speed (up to 100 kHz)

─ Fast (up to 400 kHz)

● Status flag:

─ Transmitter/receiver mode flag

─ I2C bus busy flag

─ Arbitration failure in master mode

─ Error in ACK after address/data transmission

─ False start or stop condition detected

─ Data overload or underload when clock stretching function is disabled

● 3 types of interrupts

─ 1 communication interruption

─ 1 error interrupt

─ 1 wake-up interrupt

● Wake-up function

─ In slave mode, if an address match is detected, the MCU can be woken up from low power mode

● Optional clock stretching function

3. Operation sequence required by main mode

● Set the module’s input clock in the I2C_FREQR register to generate the correct timing

● Configure the clock control register

● Configure the rise time register

● Program the I2C_CR1 register to start the peripheral

● Set the START bit in the I2C_CR1 register to 1 to generate a start condition

● The input clock frequency of the I2C module must be at least:

● Standard mode: 1MHz

● Fast mode: 4MHz

III. Software Engineering Source Code

1. About the project

The engineering code provided in this article is based on the previous software project "STM8S-A04_UART basic data transmission and reception" and adds an I2C interface. The way to read and write EEPROM is different from the previous "simulated I2C reading and writing" method.

2. Hardware I2C initialization

void I2C_Initializes(void)

{

  CLK_PeripheralClockConfig(CLK_PERIPHERAL_I2C, ENABLE);

  I2C_Cmd(ENABLE);

  I2C_Init(I2C_SPEED, I2C_SLAVE_ADDRESS7, I2C_DUTYCYCLE_2, I2C_ACK_CURR,

           I2C_ADDMODE_7BIT, 16);

}

I2C_SPEED: I2C speed, usually 100K - 400K

I2C_SLAVE_ADDRESS7: slave device address. This address has no effect when used as a master device.

I2C_DUTYCYCLE_2: Fast mode

I2C_ACK_CURR: ACK

I2C_ADDMODE_7BIT: Device address bit number

16: Input clock (unit: M)

3.EEPROM_WriteByte writes one byte

Writing a byte is divided into 5 steps:

void EEPROM_WriteByte(uint16_t Addr, uint8_t Data)

{

  while(I2C_GetFlagStatus(I2C_FLAG_BUSBUSY));

  /* 1. Start */

  I2C_GenerateSTART(ENABLE);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_MODE_SELECT));

  /* 2. Device address/write*/

  I2C_Send7bitAddress(EEPROM_DEV_ADDR, I2C_DIRECTION_TX);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));

  /* 3. Data address*/

#if (8 == EEPROM_WORD_ADDR_SIZE)

  I2C_SendData((Addr&0x00FF));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

#else

  I2C_SendData((uint8_t)(Addr>>8));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

  I2C_SendData((uint8_t)(Addr&0x00FF));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

#endif

  /* 4. Write one byte of data*/

  I2C_SendData(Data);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

  /* 5. Stop */

  I2C_GenerateSTOP(ENABLE);

}

4.EEPROM_ReadByte reads one byte

Reading a byte requires two more steps than writing a byte because when reading, there is an extra switching process from writing address to reading data.

void EEPROM_ReadByte(uint16_t Addr, uint8_t *Data)

{

  while(I2C_GetFlagStatus(I2C_FLAG_BUSBUSY));

  /* 1. Start */

  I2C_GenerateSTART(ENABLE);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_MODE_SELECT));

  /* 2. Device address/write*/

  I2C_Send7bitAddress(EEPROM_DEV_ADDR, I2C_DIRECTION_TX);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));

  /* 3. Data address*/

#if (8 == EEPROM_WORD_ADDR_SIZE)

  I2C_SendData((Addr&0x00FF));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

#else

  I2C_SendData((uint8_t)(Addr>>8));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

  I2C_SendData((uint8_t)(Addr&0x00FF));

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_BYTE_TRANSMITTED));

#endif

  /* 4. Restart */

  I2C_GenerateSTART(ENABLE);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_MODE_SELECT));

  /* 5. Device address/read*/

  I2C_Send7bitAddress(EEPROM_DEV_ADDR, I2C_DIRECTION_RX);

  while(!I2C_CheckEvent(I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED));

  /* 6. Read one byte of data*/

  I2C_AcknowledgeConfig(I2C_ACK_NONE);

  while(I2C_GetFlagStatus(I2C_FLAG_RXNOTEMPTY) == RESET);

  *Data = I2C_ReceiveData();

  /* 7. Stop */

  I2C_GenerateSTOP(ENABLE);

}

IV. Download

STM8S information:

http://pan.baidu.com/s/1o7Tb9Yq

Two versions of software source code project (STM8S-A10_I2C read and write EEPROM (hardware)):

http://pan.baidu.com/s/1c2EcRo0

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