SPI protocol configuration. How to change spi0(master) into spis0(slave) in running time?

[Sad~Sugar]

Hi all

I use nRf52840 with SDK 15.0. It allows  SPI SPIS and TWI (i2c) ,but almost 3 items in the same time. I want to use spi0 as master to configurate my other mcu and change to spis 0 as a receiver to receive data from this mcu. but the macro can't change. If I define spi0 ,I can't use spis0 anymore.  How to implement my requirement ?

[Turbo J]

That does not sould like you understood SPI in the first place. SPI always transmits and receives at the same time - you will typically just throw away the data from the path you don't need.

The clock signal defines which party is the master: The clock generator is called SPI master, the clock receiver is called the SPI slave. You don't want to mix roles.

[Sad~Sugar]

I know SPI. I need a real time communication in my project. My mcu is the producer, bursts real time data and transmit to nrf52840. If I use 52840 as master. I need to try to read data all the time to keep real time. It's unreasonable.

[Turbo J]

So just use the NRF52 always as a slave. Problem solved.

Make the other MCU pull its configuration data over SPI as the master.

You will need a properly thought out protocol anyway, because of the restrictions in the NRF52 SPIS (<=255 data bytes, CS handling, etc).

[Sad~Sugar]

1. I need to download firmware to mcu with 52840 master before mcu work.

2. I checked SDK code, and find that the data len is size_t (uint32) type in bottom code, so I changed the top code from uint8 to size_t . Now I can transmit size_t length data max in one time.

[Sad~Sugar]

If I can't change SPI into SPIS in running time, I would write a simulation SPI master to download firmware to my mcu