Conflict between boot resistors and LCD data pins.

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Conflict between boot resistors and LCD data pins.

Contributor I


the data lines of my 7" LCD have low input impedance so if I put 10K-47K pull-up boot resistors I get about 0.7V instead of 3.3V in some pins and then the uP doesn't boot in the mode it should. I've "half" solved the problem putting lower value pull-up resistors: 100ohm. On the other hand, the real problem is that LCD_CLK (LCD_RS) pin is not able to drive this load: the square wave deforms and the LCD doesn't work. If I let LCD_RS without pull-up resistor the uP boots in the right mode but I'm a little worried since the reference manual says that LCD_RS "SHOULD" be pulled-up in order to the uP don't try to boot from OTP.

I've observed the same behaviour with the EVK and with my iMX286 custom board.

Any advice? Thank you.

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