Twi configuration for multiple slave devices

RE: Twi configuration for multiple slave devices

Kartik — Mon, 22 Jul 2019 06:39:48 GMT

For all on chip sensors on the Nordic Thingy TWI_INSTANCE 0 is used.

Now if I connected the max30105 (external pulse oximeter) sensor on TWI EXT bus (pins 14 and 15), I should define a new twi_instance 1, right?

RE: Twi configuration for multiple slave devices

awneil — Thu, 18 Jul 2019 09:35:09 GMT

[quote userid="80855" url="~/f/nordic-q-a/18973/twi-configuration-for-multiple-slave-devices/199186"]as I understand it, in Nordic Thingy 52 application[/quote][quote userid="80855" url="~/f/nordic-q-a/18973/twi-configuration-for-multiple-slave-devices/199186"]all sensors except the motion sensor (lis2dh12) are interfaced on one TWI bus[/quote]

You already have a thread on this:

https://devzone.nordicsemi.com/f/nordic-q-a/49619/which-i2c-bus-is-exposed-on-nordic-thingy-52-for-custom-application-development

[quote userid="80855" url="~/f/nordic-q-a/18973/twi-configuration-for-multiple-slave-devices/199186"]For each instance a dedicated nrf_drv_twi_init() is required[/quote]

For each TWI Master instance; so one for each TWI bus.

It's the number of separate buses that matters - not what's connected to each bus.

[quote userid="80855" url="~/f/nordic-q-a/18973/twi-configuration-for-multiple-slave-devices/199186"]For each individual sensor on a TWI bus a dedicated event handler is also required[/quote]

No. Again, it's one event handler per TWI Master.

RE: Twi configuration for multiple slave devices

Kartik — Thu, 18 Jul 2019 09:17:49 GMT

So, as I understand it, in Nordic Thingy 52 application,

- all sensors except the motion sensor (lis2dh12) are interfaced on one TWI bus (TWI_SCL and TWI_SDA)

- while the motion sensor is interfaced to a different TWI bus (TWI_SCL_EXT andd TWI_SDA_EXT)

For each instance a dedicated nrf_drv_twi_init() is required?

For each individual sensor on a TWI bus a dedicated event handler is also required so that it works in non-blocking mode.

So, suppose I want to interface an I2C sensor to the default Nordic Thingy 52 application:

1. I should physically connect the sensor with TWI external bus (TWI_SCL_EXT and TWI_SDA_EXT)

2. I should use the TWI external bus instance to initialize the config params and event handler.

How come the Nordic Thingy 52 application have same twi_instance for motion sensor as that of other sensors?

RE: Twi configuration for multiple slave devices

alexSvarc — Tue, 29 Jan 2019 16:52:37 GMT

Tested my case with one TWI instance shared for both slaves, it works... So for future reference for everyone interested, if you are using only two I2C pins to connect multiple slaves you need only one TWI instance, otherwise if you are connecting the slaves on different I2C pins you need multiple TWI instances...

RE: Twi configuration for multiple slave devices

alexSvarc — Tue, 29 Jan 2019 16:03:25 GMT

i have two slaves connected on the same I2C pins on NRF52-DK, i created two I2C instances but i am unable to read/write to the two slaves, if i enable the two instances I2C stops working, does this mean that i need to share the same I2C instance for both slaves?

RE: Twi configuration for multiple slave devices

Jørgen Holmefjord — Tue, 17 Jan 2017 19:36:20 GMT

Are you able to provide a trace of the transfer from a logic analyzer? I haven't worked with AS7000, but if the transmission is aborted due to a NACK, it might be busy. Maybe you can ask the developer of the sensor?

RE: Twi configuration for multiple slave devices

Switchfeet — Tue, 17 Jan 2017 08:46:43 GMT

Thank you for your reply and reference.

As a matter of fact, I just want to utilize the current TWI instance(i.e. NRF_DRV_TWI_INSTANCE(0)), so it's no need to initiate a new TWI instance. So what I've done was unnecessary. Finally, I figure out that all I have to do is to send i2c write/read with slave address of biosensor. ;) And the biosensor is ams as7000.

But here comes another problem. When I try to send data(intel hex file) repeatedly (amount to 80KBytes) via I2C to biosensor, only about 40KBytes were transmitted successfully because of I2C timeout (i.e. NACK from as7000; maybe it's busy), I've tried to increase/decrease i2c timeout but still got 40KBytes at most. Do you have any ideas that I can try? Thanks a lot!

RE: Twi configuration for multiple slave devices

Jørgen Holmefjord — Fri, 13 Jan 2017 10:07:08 GMT

Hi,

The reason why your code is not working, is that you are initializing two TWI interfaces on the same serial interface. One address only support one interface at the time. You can see which addresses support which interfaces on this page.

You need to change the line:

static const nrf_drv_twi_t m_twi_bio = NRF_DRV_TWI_INSTANCE(0);

to:

static const nrf_drv_twi_t m_twi_bio = NRF_DRV_TWI_INSTANCE(1);

Best regards,

Jørgen