Sequential calls to nrf_drv_twi_tx fails [SDK9]

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Humberto Matias Cosentini — Sun, 30 Sep 2018 15:58:35 GMT

Hey you didn't create a new question... did you solve the problem? I believe I'm having a similar issue

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Siraj — Mon, 10 Sep 2018 16:21:07 GMT

No problem. Thanks!

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Einar Thorsrud — Mon, 10 Sep 2018 09:10:06 GMT

Hi Siraj,

Please create a new question as this is not directly related to the original thread.

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Siraj — Sun, 09 Sep 2018 20:40:20 GMT

Hi Einar! I am trying to implement your callback procedure for a sequential transaction purposes, I want to be able to send another read request as soon as the first transaction is done. First I tried the blocking mode but that is causing an internal error (Code 3). I put a time delay between transactions, and that keeps the data flowing for some time. Now, I am connecting the nRF52480 kit with the sensor board using wires (jumper wires). I know this is not the best practise but it's alright for prototyping purposes. I then tried the non-blocking mode, where a handler sets a flag to true once the Done event is received. I check for the flag in a while loop. However, more often than not, I get stuck in the while loop. The handler callback doesn't get called and the flag is not set. I think it's analogous to error code 3 I received in the blocking mode and therefore, the same cause (long wires and noise). But I just want to make sure it is what I think since I couldn't find or trace how the handler function is called back.

Thanks,

Siraj

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Einar Thorsrud — Fri, 06 Nov 2015 14:54:17 GMT

You are right. Good to hear you fond he problem.

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

robertfoss — Fri, 06 Nov 2015 14:53:17 GMT

nrf_drv_twi_tx() will not return immediately when run in blocking mode, which is is (as stated in nrf_drv_twi_init(&twi, NULL, NULL);).

However I found the issue. The flash IC I am using requires a 10ms backoff between write cycles.

RE: Sequential calls to nrf_drv_twi_tx fails [SDK9]

Einar Thorsrud — Fri, 06 Nov 2015 09:49:03 GMT

The nrf_drv_twi_tx() will always return immediately. The first call will likely return NRF_SUCCESS. Then should normally not make new call to nrf_drv_twi_tx() until you get a callback in the event handler nrf_drv_twi_init(). (As you have not supplied any event handler you will not get this event.)

When you make the second call to nrf_drv_twi_tx() immediately after the first call, the transfer is not completed, and the second call will likely return NRF_ERROR_BUSY. You do not check the return value, so you are in the blind here as well.

Your work around, waiting for some time, should work most of the time. However you do not know if you are waiting long enough or you may be waiting for far longer than you have to. Moreover there is no way to be confident that the transfer was successful as long as you do not check the callback events.

So to fix this:

Implement the event handler and provide a pointer to it in your call to nrf_drv_twi_init()
Check the return value of calls to nrf_drv_twi_tx()
Do not make a new call to nrf_drv_twi_tx() until you have received an event reporting the result of the previous call

See the TWI driver documentation for details.