SPI and TWI run out of resources

[Nick_RA]

I'm in trouble... My design has 3 SPI devices, and at a late stage I ran out of GPIO so I added a I2C I/O expander before spinning and building my PCB without thinking too much of it.

But I belatedly found out about the shared resource, so I can't add a TWI instance. 

Is it possible to dynamically reconfigure an instance between SPI & TWI? I didn't get past trying to enable in sdk_config.h as I was getting "Multiple definition of SPIM0_SPIS0_TWIM0_TWIS0_SPI0_TWI0_IRQHandler" errors.

[haakonsh]

Can you use a one SPI instance for a multiple of the SPI devices? It is a bus after all. 

[Nick_RA]

I'm guessing that would be possible with separate CS lines as one of the SPI devices isn't written to that often ... I'll have a think on that one thanks. Right now as I'll need to respin my board anyway I'm thinking along the lines of using a simple shift register for the IO (well the "O" anyway) as it's only for LEDs and relays - simple & cheap. 

[haakonsh]

There's nothing that prevents you from switching between SPI and TWI though. See the Peripheral Resource Sharing (PRS) library for instance.