FRDM K64F SPI clock pin problem

[vubdub]

Hello.

I have trouble with serial communication between  FRDM K64F and LCD 5110.

When FRDM SPI clock pin (PTD1) is connected to LCD's clock input simply via wire then clock signal  stay always low. But if you touch this clock chain in any point by some conductive object (e. g. scope probe or screwdriver) or add to pin some pull-down resistor and reset the board then SPI clock will be generated and LCD work fine.

other spi lines work without problems.

I also checked this LCD with another board  and with same wiring everything works fine without any bugs.

Can anyone explain this behavior?

[Hui_Ma]

Hi,

If the FRDM-K64F has the same digital GND with LCD 5110 board? That could be a root cause.

Wish it helps.
best regards
Ma Hui

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[vubdub]

here is my wiring

https://docs.google.com/file/d/0B8Ca28cJlc3rbnlFTzFXM2NPM1k/edit

I also tried to connect display ground to another GND pins on FRDM but it doesn't solve the problem.