TWI master does not send NACK

RE: TWI master does not send NACK

Sami — Thu, 12 Mar 2020 14:36:25 GMT

I have actually found the problem after several hours of debugging. The problem was related to line 20:

NRF_TWI1->TASKS_STOP;

The line should be as follows:

NRF_TWI1->TASKS_STOP = 1;

Then the master generates a NACK before a stop condition.

For some reason, SES does not generate any kind of warning about an empty statement. As a consequence, it took some time before I finally found the root cause of the problem.

RE: TWI master does not send NACK

Sami — Thu, 12 Mar 2020 14:33:24 GMT

Hi, I am using the TWI at the register level. If parameter ack is zero, the master initiates a stop condition. However, according to the product specification, the master also sends a NACK if a stop condition has been initiated before the byte has been read.

RE: TWI master does not send NACK

Dmitry — Thu, 12 Mar 2020 13:53:04 GMT

Hi,

I don't see how ack parameter could affect master response. NACK will be sent only for the last received byte, so you have to set MAXCNT=1 to force NACK after first byte. STOP task is not related to ACK/NACK.