版本 249b1e54d93c5fcd37a8ee333a668115c379e056
Changes from 249b1e54d93c5fcd37a8ee333a668115c379e056 to 0bea5d0505528950aa361be5aa24addc8de90cce
---
title: I2C
categories: I2C, Peripherals, STM32F4, STM32F429
...
I²C 簡介
=====================================
I²C（Inter-Integrated Circuit）是內部整合電路的稱呼，是一種串列通訊匯流排，由Philips公司在1980年代為了讓主機板、手機及嵌入式系統用以連接低速週邊裝置而發展，主要應用在board-to-board，它的設計並不能應用到長距離裝置的通訊，由於協定中從樸裝置位址只有7個位元，因此一組I²C的最多裝置位址定義至127個。
I²C只使用兩條雙向開放汲極（Open Drain）(master and slave只能把電位拉到LOW或是讓他OPEN)（串列資料（SDA）及串列時脈（SCL））並利用電阻將電位上拉。I²C允許相當大的工作電壓範圍，但典型的電壓準位為+3.3V或+5v。
I²C bus
...................
.. image:: /embedded/i2c_bus.png
藉由Master發送訊號來控制與Slave之間的通訊
I²C 特性
...................
- I²C 串列傳輸包括四個部分：起始信號、設備位址發送、數據傳送和停止信號。
- 只能Master<->Slave,無法Slave<->Slave,每個slave都要有一個特定且唯一的位址。
- START condition: SCL=High 且 SDA為負緣
- STOP condition: SCL=High 且 SDA=為正緣
.. image:: /embedded/i2c_condition.png
- 由Master發送起始信號來開起通訊，所有的slave device接收到起始信號後會進入接收數據模式。接著Master需要發送通訊目標設備的address及R/W資訊。
- STM32F429提供兩種 address mode - 7bit and 10bit
- 7bit mode: 發送 7bit 的address (MSB) 及一位元的 R(1)/W(0)後，該 address 的slave端會發送一個bit的 Ack(acknowledge) bit，ACK=0表設定成功(Slave把SDA拉到LOW)，開始數據傳送。
.. image:: /embedded/i2c_com.png
(7bit mode)
- 10bit mode: 總共用兩個byte來傳送 address資訊。第一個byte的前五個位元需為 "11110" 來表示要使用 10-bit addressing。
.. image:: /embedded/i2c_10bit.gif
(10bit mode)
- 資料傳輸
- 在 SCL 為 HIGH 時，SDA 必須是 stable 的。
- SDA 只能在 SCL 為 LOW 時改變。
- 一次傳一個 byte，每個byte都跟著一個 ACK bit ，在 ACK bit 時 Master 會釋放bus，此時 Slave 端需把 SDA 拉 LOW，否則 Master 需要發出 STOP訊號 或是重新發送 START 訊號。
- 在每個 byte 之間 Slave 端可以把 SCL 拉 LOW 來強制讓傳輸暫停。
I²C interrupt and Event
......................................
(內容待補)
.. image:: /embedded/i2c_interrupt.png
- status register
.. image:: /embedded/i2c_status_register(1).png
.. image:: /embedded/i2c_status_register(2).png
.. code-block:: c
/**
* @brief SR1 register flags
*/
#define I2C_FLAG_SMBALERT ((uint32_t)0x10008000)
#define I2C_FLAG_TIMEOUT ((uint32_t)0x10004000)
#define I2C_FLAG_PECERR ((uint32_t)0x10001000)
#define I2C_FLAG_OVR ((uint32_t)0x10000800)
#define I2C_FLAG_AF ((uint32_t)0x10000400)
#define I2C_FLAG_ARLO ((uint32_t)0x10000200)
#define I2C_FLAG_BERR ((uint32_t)0x10000100)
#define I2C_FLAG_TXE ((uint32_t)0x10000080)
#define I2C_FLAG_RXNE ((uint32_t)0x10000040)
#define I2C_FLAG_STOPF ((uint32_t)0x10000010)
#define I2C_FLAG_ADD10 ((uint32_t)0x10000008)
#define I2C_FLAG_BTF ((uint32_t)0x10000004)
#define I2C_FLAG_ADDR ((uint32_t)0x10000002)
#define I2C_FLAG_SB ((uint32_t)0x10000001)
/**
* @brief SR2 register flags
*/
#define I2C_FLAG_DUALF ((uint32_t)0x00800000)
#define I2C_FLAG_SMBHOST ((uint32_t)0x00400000)
#define I2C_FLAG_SMBDEFAULT ((uint32_t)0x00200000)
#define I2C_FLAG_GENCALL ((uint32_t)0x00100000)
#define I2C_FLAG_TRA ((uint32_t)0x00040000)
#define I2C_FLAG_BUSY ((uint32_t)0x00020000)
#define I2C_FLAG_MSL ((uint32_t)0x00010000)
(暫存器可參考 http://www.eng.auburn.edu/~nelson/courses/elec5260_6260/STM32F4%20I2C.pdf)
- I2C bus “events” from flags
I2C Master Events
.. code-block:: c
/* --EV5 */
#define I2C_EVENT_MASTER_MODE_SELECT ((uint32_t)0x00030001) /* BUSY, MSL and SB flag */
/* --EV6 */
#define I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED ((uint32_t)0x00070082) /* BUSY, MSL, ADDR, TXE and TRA flags */
#define I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED ((uint32_t)0x00030002) /* BUSY, MSL and ADDR flags */
/* --EV9 */
#define I2C_EVENT_MASTER_MODE_ADDRESS10 ((uint32_t)0x00030008) /* BUSY, MSL and ADD10 flags */
/* Master RECEIVER mode -----------------------------*/
/* --EV7 */
#define I2C_EVENT_MASTER_BYTE_RECEIVED ((uint32_t)0x00030040) /* BUSY, MSL and RXNE flags */
/* Master TRANSMITTER mode --------------------------*/
/* --EV8 */
#define I2C_EVENT_MASTER_BYTE_TRANSMITTING ((uint32_t)0x00070080) /* TRA, BUSY, MSL, TXE flags */
/* --EV8_2 */
#define I2C_EVENT_MASTER_BYTE_TRANSMITTED ((uint32_t)0x00070084) /* TRA, BUSY, MSL, TXE and BTF flags */
I2C Slave Events
.. code-block:: c
/* --EV1 */
#define I2C_EVENT_SLAVE_RECEIVER_ADDRESS_MATCHED ((uint32_t)0x00020002) /* BUSY and ADDR flags */
#define I2C_EVENT_SLAVE_TRANSMITTER_ADDRESS_MATCHED ((uint32_t)0x00060082) /* TRA, BUSY, TXE and ADDR flags */
/* Slave RECEIVER mode --------------------------*/
/* --EV2 */
#define I2C_EVENT_SLAVE_BYTE_RECEIVED ((uint32_t)0x00020040) /* BUSY and RXNE flags */
/* --EV4 */
#define I2C_EVENT_SLAVE_STOP_DETECTED ((uint32_t)0x00000010) /* STOPF flag */
/* Slave TRANSMITTER mode -----------------------*/
/* --EV3 */
#define I2C_EVENT_SLAVE_BYTE_TRANSMITTED ((uint32_t)0x00060084) /* TRA, BUSY, TXE and BTF flags */
#define I2C_EVENT_SLAVE_BYTE_TRANSMITTING ((uint32_t)0x00060080) /* TRA, BUSY and TXE flags */
/* --EV3_2 */
#define I2C_EVENT_SLAVE_ACK_FAILURE ((uint32_t)0x00000400) /* AF flag */
four I²C modes
...................
(內容待補) (要怎麼把圖縮小= =?)
以下都以7 bit adress mode 作範例
Slave transmitter
------------------------------------
.. image:: /embedded/i2c_slave_transmitter.png
Slave receiver
------------------------------------
.. image:: /embedded/i2c_slave_receiver.png
Master transmitter
------------------------------------
.. image:: /embedded/i2c_master_transmitter.png
WriteOneByte
- 產生 start bit: I2C_GenerateSTART()
- 等待EV5: while(!I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_MODE_SELECT));
- 傳送7bit address與傳輸模式: I2C_Send7bitAddress(i2cx, i2c_ADDR, I2C_Direction_Transmitter);
- 等待EV6: while(!I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));
- 傳送一個byte: I2C_SendData(I2Cx);
- 確認BYTE傳送完成: while( !I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_BYTE_TRANSMITTER) );
- 產生 stop bit: I2C_GenerateSTOP();
Master receiver
------------------------------------
.. image:: /embedded/i2c_master_receiver.png
ReadOneByte
- 產生 start bit: I2C_GenerateSTART()
- 等待EV5: while(!I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_MODE_SELECT));
- 傳送7bit address與傳輸模式: I2C_Send7bitAddress(i2cx, i2c_ADDR, I2C_Direction_Receiver);
- 等待EV6: while(!I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED));
- 確認BYTE接收完成: while( !I2C_CheckEvent(I2Cx, I2C_EVENT_MASTER_BYTE_RECEIVED) );
- 讀取暫存器: I2C_ReceiveData(I2Cx);
- 產生 stop bit: I2C_GenerateSTOP();
I²C on STM32F429-Discovery
=====================================
實驗一: touch panel
...................
觀察及使用觸控螢幕，並量測對應的i2c訊號
- `Data sheet <http://www.st.com/web/en/resource/technical/document/datasheet/CD00186725.pdf>`_
demo code:
.. code-block:: c
git clone https://github.com/colin8930/stm32_touchpanel_i2c.git
cd stm32_touchpanel_i2c
make
make flash
[stm32f429i_discovery_ioe.h]
.. code-block:: c
#define IOE_I2C I2C3
#define IOE_I2C_CLK RCC_APB1Periph_I2C3
#define IOE_I2C_SCL_PIN GPIO_Pin_8
#define IOE_I2C_SCL_GPIO_PORT GPIOA
#define IOE_I2C_SCL_GPIO_CLK RCC_AHB1Periph_GPIOA
#define IOE_I2C_SCL_SOURCE GPIO_PinSource8
#define IOE_I2C_SCL_AF GPIO_AF_I2C3
#define IOE_I2C_SDA_PIN GPIO_Pin_9
#define IOE_I2C_SDA_GPIO_PORT GPIOC
#define IOE_I2C_SDA_GPIO_CLK RCC_AHB1Periph_GPIOC
#define IOE_I2C_SDA_SOURCE GPIO_PinSource9
#define IOE_I2C_SDA_AF GPIO_AF_I2C3
#define IOE_I2C_DR ((uint32_t)0x40005C10)
stm32f429i_discovery_ioe.c:
GPIO 設定
.. code-block:: c
GPIO_InitTypeDef GPIO_InitStructure;
/* 設定RCC clock*/
/* Enable IOE_I2C and IOE_I2C_GPIO_PORT & Alternate Function clocks */
RCC_APB1PeriphClockCmd(IOE_I2C_CLK, ENABLE);
RCC_AHB1PeriphClockCmd(IOE_I2C_SCL_GPIO_CLK | IOE_I2C_SDA_GPIO_CLK |
IOE_IT_GPIO_CLK, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);
/* Reset IOE_I2C IP */
RCC_APB1PeriphResetCmd(IOE_I2C_CLK, ENABLE);
/* Release reset signal of IOE_I2C IP */
RCC_APB1PeriphResetCmd(IOE_I2C_CLK, DISABLE);
/*設定PA8、PC9 的Alternate function設為 GPIO_AF_I2C3*/
/* Connect PXx to I2C_SCL*/
GPIO_PinAFConfig(IOE_I2C_SCL_GPIO_PORT, IOE_I2C_SCL_SOURCE, IOE_I2C_SCL_AF);
/* Connect PXx to I2C_SDA*/
GPIO_PinAFConfig(IOE_I2C_SDA_GPIO_PORT, IOE_I2C_SDA_SOURCE, IOE_I2C_SDA_AF);
/* 設定 SCL、SDA pin*/
/* IOE_I2C SCL and SDA pins configuration */
GPIO_InitStructure.GPIO_Pin = IOE_I2C_SCL_PIN;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(IOE_I2C_SCL_GPIO_PORT, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = IOE_I2C_SDA_PIN;
GPIO_Init(IOE_I2C_SDA_GPIO_PORT, &GPIO_InitStructure);
I2C參數設定
.. code-block:: c
I2C_InitTypeDef I2C_InitStructure;
/* If the I2C peripheral is already enabled, don't reconfigure it */
if ((IOE_I2C->CR1 & I2C_CR1_PE) == 0)
{
/* 設定 I2C參數*/
/* IOE_I2C configuration */
I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;
I2C_InitStructure.I2C_OwnAddress1 = 0x00;
I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
I2C_InitStructure.I2C_ClockSpeed = I2C_SPEED;
/* Initialize the I2C peripheral */
I2C_Init(IOE_I2C, &I2C_InitStructure);
/* Enable the I2C peripheral */
I2C_Cmd(IOE_I2C, ENABLE);
}
touch panel demo code 一開始會先檢查 device ID及通訊是否正確
.. code-block:: c
uint16_t IOE_ReadID(void)
{
uint16_t tmp = 0;
/* Read device ID */
tmp = I2C_ReadDeviceRegister(0);
tmp = (uint32_t)(tmp << 8);
tmp |= (uint32_t)I2C_ReadDeviceRegister(1);
/* Return the ID */
return (uint16_t)tmp;
}
.. code-block:: c
uint8_t I2C_ReadDeviceRegister(uint8_t RegisterAddr)
{
uint8_t tmp = 0;
/* Enable the I2C peripheral */
I2C_GenerateSTART(IOE_I2C, ENABLE);
/* Test on EV5 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_SB));
/* Disable Acknowledgement */
I2C_AcknowledgeConfig(IOE_I2C, DISABLE);
/* Transmit the slave address and enable writing operation */
I2C_Send7bitAddress(IOE_I2C, IOE_ADDR, I2C_Direction_Transmitter);
/* Test on EV6 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_ADDR));
/* Read status register 2 to clear ADDR flag */
IOE_I2C->SR2;
/* Test on EV8 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_TXE));
/* Transmit the first address for r/w operations */
I2C_SendData(IOE_I2C, RegisterAddr);
/* Test on EV8 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while ((!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_TXE)) || (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_BTF)));
/* Regenerate a start condition */
I2C_GenerateSTART(IOE_I2C, ENABLE);
/* Test on EV5 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_SB));
/* Transmit the slave address and enable writing operation */
I2C_Send7bitAddress(IOE_I2C, IOE_ADDR, I2C_Direction_Receiver);
/* Test on EV6 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_ADDR));
/* Read status register 2 to clear ADDR flag */
IOE_I2C->SR2;
/* Test on EV7 and clear it */
IOE_TimeOut = TIMEOUT_MAX;
while (!I2C_GetFlagStatus(IOE_I2C, I2C_FLAG_RXNE));
/* End the configuration sequence */
I2C_GenerateSTOP(IOE_I2C, ENABLE);
/* Load the register value */
tmp = I2C_ReceiveData(IOE_I2C);
/* Enable Acknowledgement */
I2C_AcknowledgeConfig(IOE_I2C, ENABLE);
/* Return the read value */
return tmp;
}
(待補)
SCL: PA8
SDA: PC9
slave address: 0x82 (0x01000010)
.. image:: /embedded/i2c_picture.jpg
.. image:: /embedded/scope_5.jpg
start bit -> send address and transmitter bit -> ack -> senddata(register address 0x00)
.. image:: /embedded/scope_6.jpg
start bit -> send address and receiver bit -> ack -> data send by slave
.. image:: /embedded/scope_8.jpg
stop bit -> start bit -> send address and transmitter bit -> ack -> senddata(register address 0x01)
.. image:: /embedded/scope_9.jpg
start bit -> send address and receiver bit -> ack -> data send by slave
.. image:: /embedded/scope_12.jpg
改變I2C CLOCK SPEED -> 400kHz
.. image:: /embedded/scope_14.jpg
要注意探棒衰減...
實驗二: 兩塊(以上)板子的數據傳輸
...................
一塊板子當作Master，其他的作為Slave，實驗I2C的資料傳輸
(待補)
(NVIC ＆ I2C interrupt)
Reference
=====================================
- `reference_manual <http://www.st.com/web/en/resource/technical/document/reference_manual/DM00031020.pdf>`_
- `wikipedia <http://zh.wikipedia.org/wiki/I%C2%B2C>`_
- `http://www.eng.auburn.edu/~nelson/courses/elec5260_6260/STM32F4%20I2C.pdf <_http://www.eng.auburn.edu/~nelson/courses/elec5260_6260/STM32F4%20I2C.pdf>`_
