Unable to Get Clock Pulse on the MCU

[SidMishra]

Hi Team, 

We are using KS20/22 Series of MCU along with FTDI chip which is connected through a Multiplexer with the MCU on a Custom Designed Board.

Our aim is to get data to the MCU via FTDI  Chip which is connected to the MCU on SPI bus. We are using the MCU acting as a Slave device and we are running SPI Half-Duplex Code on the MCU which is available in the SDK downloaded from the NXP Website. Here the issue that we came across is that we are unable to get any clock pulses over the channel when measuring through an Oscilloscope. Awaiting a solution for the same.

Attaching a Snap of our Schematic for reference.

Thanks !

[myke_predko]

Hey @SidMishra 

Just to confirm that you're able to talk to the MCU for programming and debugging? 

I presume you're referring to the SPI CLK which should be generated by U1 and going through U18 on its way to the K20 (U16)?  Have you scoped it from U1 to U18 and then from U18 to U16?  

If it's a problem from U18 to U16 then I would first check the voltage level on U16's S (Pin 1) to make sure the right output is selected.  If it's not that, check your pin mux value for U18's Pin 77 (PTC5) - could it be a GPIO output instead of a SPI CLK (which makes it a high impedance input).  

Good luck!