TWI. RXDREADY event signaled, TXDSENT - not.

[anv]

I am trying to communicate with DS1307 (RTC) using TWI on nRF51822. I have configured the pins, address (0x68 fixed for DS1307), frequency and enabled TWI.

Now I am about to read the register 0x00 of the slave (DS1307) I suppose I should start transmission task (write 0x01 to STARTTX, 0x40004008), this will cause TWI to clock out address and "write bit" (I should not take care of it), then I should write the value (0x00: register to be read from DS1307) into the TXD, and TWI will clock it out and signal TXDSENT event. But I see in TWI1 debug window, that only the RXDREADY is being signaled, TXDSENT - not. Any idea, please.

[Susheel Nuguru]

TXDSENT is only signaled if the peer has ACKed the transmitted packet. Are you use that the byte sent is ACKed by DS1307?

[anv]

How can I check it? And how could it happen, that RXDREADY has been signaled?

[Susheel Nuguru]

you can connect a logic analyzer or similar to the TWI pins and sniff the transaction. No just the ACK from the peer does not give RXDREADY event. RXDREADY is received only if data is read from the sensor after explicitly requesting it.

[anv]

Thank you Aryan! I have not got any logical analyzer, but I see I need it anyway. Could you please suggest me some inexpensive type? What should be taken into account? Maybe I would better publish a new question...

[Susheel Nuguru]

I use Saleae logic analyzer and you can get it from 100$.