twi transmission address never shows correctly as i set

[abcdcadb]

my TWI device sensor, both its writing and reading address is 0x55. This seems weird for library of nRF since the last bit should be set as 0 for transmission and 1 for receiving (as below link)

https://devzone.nordicsemi.com/f/nordic-q-a/6431/unusual-twi-i2c-problem

However, that is the configuration of that device and I can't change. According to their document, just send 0x55,0xaa and 0x55, then get data. But for nordic, the data i caught from scope is 0x54,0xaa and 0x55 (0x55 is changed into 0x54 because of transmission)

I would like to know if i can send directly via TWI (dont care about address) 0x55,0xaa and 0x55 and then capture data as their sample code and how

thanks

[karthikeyan]

hi,

  i have converted that data sheet in english and checked the default i2c address is 0x55 for read. so for write it will be ox54(may be i can be wrong). i will attach the data sheet. please check that.

zm03 docu.docx

regards,

karthikeyan

[abcdcadb]

they send 0x55 directly as byte doesn't matter it is write or read, that is the problem,

anyway, i changed sensor but if possible I still want to know can nordic send directly byte?

[tesc]

Hi,

No, it is not possible to break that part of the TWI specification. The TWI peripheral operates with a 7 bit address and a read/write bit, and because this is done in hardware it cannot change.

Regards,
Terje

[abcdcadb]

hi tesc and karth

i am at vacation thus i come back to finish this issue.

according to the translated document of karth, i read data at 0x55 and 0xaa in turn and still receive nothing, any idea else?