repeated start for twi master rx operation

RE: repeated start for twi master rx operation

Aurele — Tue, 02 Jun 2020 09:01:57 GMT

Hi,

I'm also facing the same issue since i want to interface with the azotech IQS263. The sensor reacts on the first stop condition it detects and close its communication window so i absolutly need to make a restart after a I2C read if i want to read several registers within a communication window.

For now, i'm stuck !

Regards,

RE: repeated start for twi master rx operation

JW de Wit — Mon, 16 Jul 2018 11:23:48 GMT

I have got the same problem (azoteq IQS360A touch chip).

I got it solved by using the PPI to generate a STARTTX tastk on an BB event.

PS. I don't use the SDK

RE: repeated start for twi master rx operation

Yu Peng — Wed, 11 Oct 2017 23:28:58 GMT

In short, after retrieving the last rxd byte you should run NRF_TWI0->TASKS_SUSPEND = 1;

Then reset the twi hardware nrf_drv_twi_uninit(&m_twi);

and reconfigure it through nrf_drv_twi_init(&m_twi, &twi_zeus2_config, NULL, NULL); nrf_drv_twi_enable(&m_twi);

lastly NRF_TWI0->TASKS_RESUME = 1;

before starting the next rx transaction

RE: repeated start for twi master rx operation

Keton — Fri, 16 Sep 2016 15:06:19 GMT

maybe trough direct manipulation of registers/ppi tasks but AFAIK there's no 'easy way' of doing that in SDK11 via library or driver code

RE: repeated start for twi master rx operation

George Leung — Fri, 16 Sep 2016 14:33:16 GMT

It may be unusual but that is what I want, instead of a stop, I need a repeated start for next read sequence. Is that any tricks I can do that?

RE: repeated start for twi master rx operation

Keton — Fri, 16 Sep 2016 14:10:54 GMT

As far as I know SDK doesn't support "no stop RX". Also I haven't seen use case for such feature in real life and I do quite a lot of I2C peripheral drivers. Are you sure that no stop condition after rx is really what you want?

RE: repeated start for twi master rx operation

George Leung — Fri, 16 Sep 2016 13:46:39 GMT

don't care too much about the term "register", it just one byte memory address of the touch sensor which I am going to read. nrf_drv_twi_tx with no_stop is good but how about nrf_drv_twi_rx? I don't want any stop between each read operation. As I send a stop the sensor chip will perform next measurement which is not desire.

RE: repeated start for twi master rx operation

Keton — Fri, 16 Sep 2016 12:44:01 GMT

I2C protocol doesn't have a concept of registers. All bytes you transmit are raw data and peripheral interprets them according to its specification. Unless your I2C device is very weird and uncommon, You really want to do following seq:

TX: register 1 OPcode
Repeated start
RX: register 1 contents
STOP
repeat for register 2

for info how to do it consult infocenter.nordicsemi.com/.../hardware_driver_twi.html and use either blocking calls of nrf_drv_twi_tx with no_stop set to true + nrf_drv_twi_rx or async NRF_DRV_TWI_XFER_TXRX. There are SDK examples which show this in more detail.

RE: repeated start for twi master rx operation

George Leung — Fri, 16 Sep 2016 12:17:54 GMT

Let's me provide some more detail about the operation, the sequence should be that: Start Addr+W ACK registerA ACK Start Addr+R ACK data1 ACK datan NACK Start Addr+W ACK registerC ACK Start Addr+R ACK data1 ACK data...n NACK .... Start Addr+W ACK registerX ACK Start Addr+R ACK data1 ACK datan NACK Stop The major issue is I don't want to send a stop when last byte of current register read. Is it possible?

RE: repeated start for twi master rx operation

Keton — Fri, 16 Sep 2016 08:51:16 GMT

if register X means that you have to send some opcode to the I2C slave then you are actually making a write operation so just use TX_RX xfer in either app_twi of nrf_drv_twi_xfer