topic Re: mosi voltage level in Kinetis Microcontrollers

mosi voltage level

carlesricart — Wed, 21 Oct 2015 14:28:55 GMT

Hi,

I'm working with frdm k20D50M. I'm using the Spi, and my MOSI line has the 3.3V max level, and 2.4V low level.

I would like to work with a 0v low level. How do this? with and external translator? there are another possibility?

Thanks

Re: mosi voltage level

davidsherman — Wed, 21 Oct 2015 16:04:28 GMT

Is your device damaged, or is something pulling it up? Unless you have an unusually strong pull up, it should be close to zero on a logic low and no translation is necessary. Make sure also that the pin muxing has that pin configured as MOSI, not a digital input. Are you seeing serial data being sent on that line?

Re: mosi voltage level

xiangjun_rong — Thu, 22 Oct 2015 03:55:20 GMT

Hi,Carles,

As David said that It is strange that the MOSI pin can not pull to LOW logic, pls check if the pin is connected to a diode, your phenomenon seems that the pin is connected to a diode or the pin is damaged.

The SPIx_OUT(MOSI) is a push-pull pin if you clear the ODE bit in corresponding PORTx_PCRn register, even if you set the pin in open drain mode, it means that the High logic can not reach if you do not enable pull-up resistor.

Hope it can help you.

XiangJun Rong

Re: mosi voltage level

carlesricart — Thu, 22 Oct 2015 08:09:43 GMT

Hi,

Something happens with the port, I changed to another one and it works. I take the port directly from the connector in either case.

It's weird becouse the frdm is new!

thanks you both!