MSP430F5326: SPI 3 wires mode connection

Hi Ryder,

Referring to the MSP430F5xx_6xx user's guide, there is an illustration showing the recommended connections.

Can you tell me more about the sensor you are using?  You may only need to connect the UCxSIMO, UCxMISO and UCxCLK pins.

Hi!
Im using BME680 from Bosch in spi 3wire mode

Thanks
Ryder

This looks about right, but I don't think you need the resistor on MISO (since it will be hi-Z anyway).

Last I looked, the USCI didn't really support 3-wire natively -- there's no mechanism for telling it to turn the line around -- so I think you'll have to do that yourself. The simplest way is probably to wiggle PxSEL for MOSI between bytes, effectively taking MOSI away from the USCI to turn the line around.

I have to ask: Is 3-wire a requirement for your project? Given that the BME680 can do 4-wire, it seems like you're doing it the Hard Way.

Hi Anh,

Yes, the 3-wire connections should work. For the MSP430F5326, you can operate it in the "4-pin" mode, which means you will connect the UCxSTE pin to the BOSCH_CSB pin. Or you can use the "3-pin" mode and control the BOSCH_CSB pin with a general purpose IO pin. I think you are best to use "4-pin" mode to make it simple.