Resource allocation

RE: Resource allocation

haakonsh — Tue, 17 Sep 2019 12:05:37 GMT

You can use any peripherals given that they do not share registers in RAM.
Since SPIM0/1, TWIM0/1, and TWIS0/1 share registers you cannot use them at the same time. You must, therefore, use only one TWIM bus.

By looking at the base address of an instance, found in the peripheral's Registers chapter, we can find a solution where two instances does not overlap:

TWIM0 or TWIS0, 0x40003000
TWIM1 or TWIS1, 0x40004000
SPIM2 , 0x40023000
SPIM3 , 0x4002F000

RE: Resource allocation

awneil — Mon, 16 Sep 2019 16:10:53 GMT

[quote userid="75383" url="~/f/nordic-q-a/52186/resource-allocation/209900"]What do you mean by "required number of hardware devices" ?[/quote]

A TWI controller is a physical bit of hardware on the silicon.

Likewise SPI.

The nRF52840 (like any other microcontroller) has a finite and fixed number of these physical bits of hardware on the silicon.

The Product Specification tells you what the number is.

RE: Resource allocation

ran — Mon, 16 Sep 2019 15:52:02 GMT

The I2C is going to an FPGA and from there multiplexed.

What do you mean by "required number of hardware devices" ? We are using nrf52840 chip

RE: Resource allocation

awneil — Mon, 16 Sep 2019 15:49:00 GMT

I2C isn't really intended to off-board connections.

Note that you can get TWI multiplexers & bridges ...

PRS won't help if the chip doesn't have the required number of hardware devices.

RE: Resource allocation

ran — Mon, 16 Sep 2019 15:41:57 GMT

Thanks.

I have one TWIM routed to an outside connector and another one to on-board Slave ( RTC \ EEPROM )

Should I enable PRS module to over-come resource sharing conflict ?

RE: Resource allocation

awneil — Mon, 16 Sep 2019 14:41:21 GMT

Surely, the Product Specification tells you how many SPI and TWI hardware modules are available?

[quote userid="75383" url="~/f/nordic-q-a/52186/resource-allocation"]2 TWIM Master[/quote]

Why do you need two?

The whole point of TWI as a bus is that it one Master can communicate with multiple Slaves.

Similarly for SPI although, being less well defined, some peripherals might not play nicely together