Manuel Martinez

Conflict between boot resistors and LCD data pins.

Discussion created by Manuel Martinez on Apr 11, 2012


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.