I2C 使用Microchip plib

本篇以dsPIC30F為主。

plib 安裝

到Legacy PIC24 MCU & dsPIC DSC Peripheral Library下載最新的plib，然後她會要求將plib安裝到你電腦中xc16 complier的資料夾下(linux在”/opt/microchip/xc16”下)。

函式概覽

安裝後文件會在xc16 complier的docs/periph_libs下。
其中plib提供以下函式。

AckI2C
CloseI2C
ConfigIntI2C
DataRdyI2C
IdleI2C
MastergetsI2C
MasterputsI2C
MasterReadI2C
MasterWriteI2C
NotAckI2C
OpenI2C
RestartI2C
SlavegetsI2C
SlaveputsI2C
SlaveReadI2C
SlaveWriteI2C
StartI2C
StopI2C

還有一些MARCO

EnableIntMI2C
DiableIntMI2C
SetPriorityIntMI2C
EnableIntSI2C
DisableIntSI2C
SetPriorityIntSI2C

這份文件16 bit language tools第191頁開始有詳述這些函式的介面。所以本文主要會面向如何運用這些函式達成master與slave溝通。

I2C (dsPIC30F as Master with 7bit address)

reception

以下圖片來自於http://ww1.microchip.com/downloads/en/DeviceDoc/70046E.pdf

對應到plib的流程為。(以下為我在i2cdevlib中所新增的片段，為一次讀多個bytes)。

	Master |S |Device Addr+W| |Reg Addr| |S |Device Addr+R| | |NACK|P|
	Slave | | |ACK| |ACK| | |ACK|DATA| | |

view raw I2C_read_seq hosted with ❤ by GitHub

請先透過ConfigIntI2C和OpenI2C設定好硬體參數。

	IFS0bits.MI2CIF = 0;
	IEC0bits.MI2CIE = 0;
	/*master Start*/
	StartI2C();
	/* Clear interrupt flag */
	/* Wait till Start sequence is completed */
	while(I2CCONbits.SEN);
	/*master send AD+W*/
	/* Write Slave Address (Write)*/
	MasterWriteI2C(devAddr << 1 | 0x00);
	/* Wait until address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send Ack*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	while(I2CSTATbits.ACKSTAT);
	/*Master send RA*/
	/* Write Register Address */
	MasterWriteI2C(regAddr);
	/* Wait until address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send ACK*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	while(I2CSTATbits.ACKSTAT);
	/*Master Pause*/
	StopI2C();
	/* Wait till stop sequence is completed */
	while(I2CCONbits.PEN);
	/*Master Start*/
	StartI2C();
	/* Wait till Start sequence is completed */
	while(I2CCONbits.SEN);
	/*Master send AD+R*/
	/* Write Slave Address (Read)*/
	MasterWriteI2C(devAddr << 1 | 0x01);
	/* Wait until address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send Ack*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	while(I2CSTATbits.ACKSTAT);
	data[0] = MasterReadI2C();
	unsigned int i;
	for (i = 1 ; i < length ; i++ ){
	AckI2C();
	while(I2CCONbits.ACKEN == 1);
	data[i] = MasterReadI2C();
	}
	NotAckI2C();
	while(I2CCONbits.ACKEN == 1);
	/*Master Pause*/
	StopI2C();
	/* Wait till stop sequence is completed */
	while(I2CCONbits.PEN);

view raw I2C_read.cpp hosted with ❤ by GitHub

值得注意的是在dsPIC30F manual中第5步驟。要透過StartI2C再次產生start condition。而讀入多個data bytes可用MastergetsI2C函式。

transmission

transmission只要全部都由Master端給資料即可。
對應到plib的流程為。(以下為我在i2cdevlib中所新增的片段，為一次寫多個bytes)。

	Master |S |Device Addr+W| |Reg Addr| |DATA| |P|
	Slave | | |ACK| |ACK| |ACK | |

view raw I2C_write_seq hosted with ❤ by GitHub

請先透過ConfigIntI2C和OpenI2C設定好硬體參數。

	IFS0bits.MI2CIF = 0;
	IEC0bits.MI2CIE = 0;
	/*Master Start*/
	StartI2C();
	/* Wait util Start sequence is completed */
	while(I2CCONbits.SEN);
	/* Clear interrupt flag */
	IFS0bits.MI2CIF = 0;
	/*Master send AD+W*/
	/* Write Slave address (Write)*/
	MasterWriteI2C(devAddr << 1 | 0x00);
	/* Wait till address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send ACK*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	while(I2CSTATbits.ACKSTAT);
	/*Master send RA*/
	/* Write Slave address (Write)*/
	MasterWriteI2C(regAddr);
	/* Wait till address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send ACK*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	while(I2CSTATbits.ACKSTAT);
	/*Master send data*/
	/* Transmit string of data */
	uint8_t i;
	for (i = 0 ; i < length ; i++){
	MasterWriteI2C(data[i]);
	/* Wait till address is transmitted */
	while(I2CSTATbits.TBF); // 8 clock cycles
	/*Slave send ACK*/
	while(!IFS0bits.MI2CIF); // Wait for 9th clock cycle
	IFS0bits.MI2CIF = 0; // Clear interrupt flag
	}
	StopI2C();
	/* Wait till stop sequence is completed */
	while(I2CCONbits.PEN);

view raw I2C_write.cpp hosted with ❤ by GitHub

Written with StackEdit.

MPU6050 Gyroscope/Accelerometer 使用筆記

特性與參數

• 用途：量測姿態
• 精度：
  
  • Gyro : 250/500/1000/2000 dps (degree per second)
  • Accel : +-2/4/6/16 g
• 輸出資料：為angular rate(角速度) ，16bit , LSB/g
• 原始感應器電壓VDD(僅有晶片)：2.375V-3.46V
• 原始晶片通訊電氣參數：
  
  • Vlogic = 1.8V (+-5%) OR VDD
  • VIH(Voltage high level) : 必須超過0.7*Vlogic(MPU6050)
  • VIL(Voltage low level):必須低於0.3*Vlogic(MPU6050)
  • Ci(Input Capacitance): <5pF
  • I2C address: 1101000(when AD0 = 0),1101001(when AD0 = 1)
  • I2C最快頻率：400KHZ
• 模組(GY521)電壓：3~5V
• 其他特色：
  
  • 有內建low pass filter可供程式選擇
  • 中斷信號選擇
  • Auxiliary I2C port可與其他模組串接
  • 可作自我校正
  • 可透過FSYNC pin與外部模組做synchronization (Gyro)
  • On-chip DIgital motion processor
  • 有內建FIFO
• 通信方式：I2C(MPU6050,MPU6000)/SPI(MPU6000)
• 晶片datasheet:連結在此

資料單位換算

Gyroscope

首先先看下表為MPU6050 datasheet。

最重要的是scale factor。
透過公式

Gyro_value = (Data Register value) / (Scale factor)

其中單位為degree/second

Accelerometer

首先先看下表

一樣，最重要的是scale factor。
透過公式

Accel_value = (Data Register value) / (Scale factor)

其中單位為g

軟體應用方式

Ardunio使用i2cdevlib。運用其中的MPU6050 lib來溝通。其中，可以安裝processing IDE並開啟i2cdevlib的examplelink，這樣你可獲得一個有小飛機形狀的gui，她會呈現感測器的當前姿態。
dsPIC30F也可以使用i2cdevlib，近日有開始支援MPU6050。
而MPU6050的digital motion proccesor是其一大亮點。透過開啟這個功能，你可以透過interrupt直接獲得sensor當前姿態。她會幫你將角加速度轉成角度，這樣你就不用一直輪詢了。(輪詢計算範例：L3G4200)。

Written with StackEdit.