如何通過MAX2990 I2C接口向標(biāo)準(zhǔn)EEPROM (24C04)連接
引言
本文引用地址:http://m.butianyuan.cn/article/173171.htm本文介紹了如何通過MAX2990電力線通信調(diào)制解調(diào)器的I2C接口與外部EEPROM 24C04連接,并給出了相應(yīng)的固件例程。I²C總線受控于MAX2990 (主機(jī)),24C04 EEPROM為從機(jī)器件。以下框圖給出了本文示例的硬件配置。
固件說明
I²C接口初始化
一旦使能I²C模塊,SCL和SDA必須配置成漏極開路狀態(tài),以確保I²C總線通信正常。由于I²C是GPIO端口的一個替代功能,固件必須確保SCL和SDA輸入在初始化期間禁止上拉(通過對端口控制器的輸出位寫零實現(xiàn))。
示例中,時鐘頻率為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
寫模式
寫入24C04 EEPROM時,必須通過I²C接口寫入以下字節(jié):
- EEPROM的I²C總線地址(這里為0xA0)
- EEPROM存儲器的地址
- 數(shù)據(jù)字節(jié)(地址將自動遞增)
示例中試圖寫入以下字節(jié),從0x00地址開始,向EEPROM寫入: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
讀取我們寫入EEPROM的數(shù)據(jù)時,為24C04留出足夠的寫時間非常關(guān)鍵。通常在“停止條件”后留出幾個毫秒的時間,請參考數(shù)據(jù)資料,確認(rèn)您的時間設(shè)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
評論