关于i2c bit ops的疑问

发布于 2014-06-12 00:21:54 浏览：2030 订阅该版

平台：stm32f207 + AT24MAC402（eeprom）

碰到的问题：
    
      1 设备地址问题，i2c的bit操作中，设备地址是不包括最低位的。也即是说如果高四位为1010，而A2 A1 A0 = 001,那么device id  为1010001 = 0x51；

2 采用aozima提供的测试例子（https://club.rt-thread.org/ask/question/3471.html）操作，能够读取数据，但是写不不了数据，写保护已经取消。打印信息如下：```i2c_test()
i2c_test()
msgs[0] W, addr=0x51, len=1犤
msgs[1] R, addr=0x51, len=2犤
send start condition
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
write 1 byte
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
recieve bytes: 0xff, ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
recieve bytes: 0xff, NACK
read 2 bytes
send stop condition
read EEPROM at I2C address: 0x51
0x0000: FF FF 
00 00 msgs[0] W, addr=0x51, len=1?
                                   msgs[1] W, addr=0x51, len=2?
                                                                send start condition
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
write 1 byte
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
write 2 bytes
send stop condition
msgs[0] W, addr=0x51, len=1?
                             msgs[1] R, addr=0x51, len=2?
                                                          send start condition
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
write 1 byte
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
recieve bytes: 0xff, ACK
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
wait 3 tick for SCL line to go high
recieve bytes: 0xff, NACK
read 2 bytes
send stop condition
re-read EEPROM at I2C address: 0x51
0x0000: FF FF ```