Multimaster I2C communication

RE: Multimaster I2C communication

Stian Røed Hafskjold — Mon, 13 Dec 2021 15:53:00 GMT

Hi Jostikas, that is correct. In hardware context you enable either TWI slave or TWI master which are two different peripherals.

However, it is possible to switch between TWI master and TWI slave peripherals during software runtime. So the TWI slave can be configured as the default peripheral, and then switch to TWI master if data should be read or written on the bus. This will have to be implemented in software and would probably not be robust against collisions on the bus.

RE: Multimaster I2C communication

Jostikas — Mon, 13 Dec 2021 14:10:02 GMT

Well, no. I2C is a bus topology, where "master" is the device that first started driving the clock (if there was no contention) or the device that won arbitration (if there was contention for the bus) and every other device is a slave. And these terms are only valid for the duration of one transaction. Multi-Master simply means there are multiple devices that can initiate transfers on the bus, and there's no reason the sometimes-masters can't talk to each other, if they have assigned addresses.

The correct answer is that Nordic's "TWI" peripheral is not actually I2C multimaster compatible.

EDIT: Sorry, I assumed the response was from a Nordic employee.

RE: Multimaster I2C communication

Nguyen Hoan Hoang — Fri, 02 Feb 2018 00:19:11 GMT

The best solution for that is to use UART. It is bi-directional. It will interrupt on receive and send is independent sot both can send and listen at the same time. The nRF can handle 1 MBaud.

RE: Multimaster I2C communication

carlf — Fri, 02 Feb 2018 00:13:49 GMT

I need either MCU to be able to initiate communication. The issue with a Master/Slave configuration is that the Slave needs to wait for the Master to initiate the communication.

RE: Multimaster I2C communication

Nguyen Hoan Hoang — Fri, 02 Feb 2018 00:10:09 GMT

I am not sure to fully understand what you want to do exactly. If just to transfer data between 2 MCUs, there are many ways. I2C (Master/Slave), SPI (Master/Slave) or UART. Multimaster means 2 MCU in master mode trying to access the peripherals on the same bus not for talking to each other.