TWIS instances

[Anisa]

Hi,

I have a situation where I have to create 4 TWIS instances on nRF52832.

sdk_config.h only shows 2 TWIS instances.

// <q> TWIS0_ENABLED  - Enable TWIS0 instance
 

#ifndef TWIS0_ENABLED
#define TWIS0_ENABLED 0
#endif

// <q> TWIS1_ENABLED  - Enable TWIS1 instance
 

#ifndef TWIS1_ENABLED
#define TWIS1_ENABLED 1
#endif

Is it ok if I add other instances (TWIS2_ENABLED and TWIS3_ENABLED) in sdk_config myself (haven't tried it yet)

If not, how can I access 4 TWIS devices if I only create 1 instance of TWIS?

[awneil]

Look in the Product Specification - it tells you how many TWIS hardware blocks are present in the chip. You can't have more than that!

But note that the Product Spec also says:

"The TWI slave is able to listen for up to two addresses at the same time"

So maybe you could have 2 instances each listening to 2 addresses ... ?

[ovrebekk]

Hi Anita

I am a bit confused whether or not you need the nRF52832 to be the TWI master or slave. 

Do you really have 4 TWI master devices that all need to talk to the nRF52, or do you have 4 TWI slaves that you are trying to connect to the nRF52?

Normally your controller (ie the nRF52) would be the master on the bus, and your sensors would be slaves. 
In this configuration you can use a single master on the nRF52 device to communicate to all your slaves, since TWI allows a single bus to be shared between devices. 

Best regards
Torbjørn

[awneil]

ovrebekk said:

you can use a single master on the nRF52 device to communicate to all your slaves, since TWI allows a single bus to be shared between devices.

Indeed:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/twim.html#concept_scx_f5p_xr__fig_swz_gvp_xr

[Anisa]

May be I should explain further in detail. My 4 slaves are sharing the same I2C bus. They all have different I2C address. In this case, should I create 4 twis instances or only 1 twis instance?

I understood it should be 1 instance. How should I define I2C address of slaves, initialize and enable?

[awneil]

Still not entirely clear, I'm afraid - a diagram is a far more effective way of conveying this sort of information!

In particular, is the nRF52 is the Master on the I2C bus?

Anisa said:

They all have different I2C address

Of course they do - that is a fundamental requirement of any I2C bus!

https://www.nxp.com/docs/en/user-guide/UM10204.pdf

https://en.wikipedia.org/wiki/I%C2%B2C