如何通過(guò)MAX2990 I2C接口向標準EEPROM (24C04)連接

　　引言

　　本文介紹了如何通過(guò)MAX2990電力線(xiàn)通信調制解調器的I2C接口與外部EEPROM 24C04連接，并給出了相應的固件例程。I²C總線(xiàn)受控于MAX2990 (主機)，24C04 EEPROM為從機器件。以下框圖給出了本文示例的硬件配置。

　　固件說(shuō)明

　　I²C接口初始化

　　一旦使能I²C模塊，SCL和SDA必須配置成漏極開(kāi)路狀態(tài)，以確保I²C總線(xiàn)通信正常。由于I²C是GPIO端口的一個(gè)替代功能，固件必須確保SCL和SDA輸入在初始化期間禁止上拉(通過(guò)對端口控制器的輸出位寫(xiě)零實(shí)現)。

示例中，時(shí)鐘頻率為250kHz。首先需要配置MAX2990的I²C接口：

PO1_bit.Bit2 = 0; 		// Disables the GPIO function of thePO1_bit.Bit3 = 0; 		// I2C pinsI2CCN_bit.I2CEN = 0; 	// Makes sure that I2C is disabled// to allow the changing of the I2C settingsI2CCN_bit.I2CMST = 1; 		// Sets the I2C engine to master modeI2CCN_bit.I2CEA = 0; 		// 7-bit address modeI2CCK_bit.I2CCKL = 0x40; 	// 2µs CLK-low, to define I2C frequencyI2CCK_bit.I2CCKH = 0x40; 	// 2µs CLK-high, to define I2C frequencyI2CTO = 200; 		// I2C_TIMEOUTI2CST = 0x400; 		// Resets I2C status registerI2CCN_bit.I2CEN = 1; 		// Enables the I2C engine

寫(xiě)模式

寫(xiě)入24C04 EEPROM時(shí)，必須通過(guò)I²C接口寫(xiě)入以下字節：

1. EEPROM的I²C總線(xiàn)地址(這里為0xA0)
2. EEPROM存儲器的地址
3. 數據字節(地址將自動(dòng)遞增)

示例中試圖寫(xiě)入以下字節，從0x00地址開(kāi)始，向EEPROM寫(xiě)入：0x12、0x34、0x56、0x78和0x90。

i2c_init_write(); 	// Sets the MAX2990 I2C Engine into write modei2c_write(0x50); 	// 24C04 write (adr = 0b1010 000 0) = 0xA0// The MAX2990 I2C engine shifts the I2C address by// 1 bit, because it will generate the R/W bit// automaticallyi2c_write(0x00); 	// word address locationi2c_write(0x12); 	// data1i2c_write(0x34); 	// data2i2c_write(0x56); 	// data3i2c_write(0x78); 	// data4i2c_write(0x90); 	// data5I2C_STOP; 		// Sends I2C stop-condition

讀模式

讀取我們寫(xiě)入EEPROM的數據時(shí)，為24C04留出足夠的寫(xiě)時(shí)間非常關(guān)鍵。通常在“停止條件”后留出幾個(gè)毫秒的時(shí)間，請參考數據資料，確認您的時(shí)間設置符合IC的要求。

i2c_init_write(); 	// Sets the MAX2990 I2C engine into write modei2c_write(0x50); 	// 24C04 write (adr = 0b1010 000 0) = 0xA0// The MAX2990 I2C engine shifts the I2C address by// 1 bit, because it will generate the R/W bit// automaticallyi2c_write(0x00); 	// word address locationi2c_init_read(); 	// Sets the MAX2990 I2C engine into read modei2c_write(0x50); 	// 24C04 read (adr = 0b1010 000 1) = 0xA1// The MAX2990 I2C engine shifts the I2C address by// 1 bit, because it will generate the R/W bit// automaticallyunsigned char data[5]; 	// Array to store the received datai2c_read(data[0]); // Reads 1 byte from I2C and writes it to the arrayi2c_read(data[1]); // Reads 1 byte from I2C and writes it to the arrayi2c_read(data[2]); // Reads 1 byte from I2C and writes it to the arrayi2c_read(data[3]); // Reads 1 byte from I2C and writes it to the arrayi2c_read(data[4]); // Reads 1 byte from I2C and writes it to the arrayI2C_STOP; 		// Sends I2C stop-condition
				
            

				
					
					
				
			
                
			
							

                
			            

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