BBB won't boot when LCD is connected

[lix...@gmail.com]

Hello, Everyone.

I am in the very early stages of interfacing the BBB with a new 4.3" TFT LCD, not a cape.  It has a 16-bit data bus setup for 6800 style interface with the onboard controller (SSD1963).  This winds up requiring 22 GPIO pins.  I have been an engineer in the LCD industry for 6 years now, so I know my way around most types of LCDs and configurations...but I am a relative newbie to the BBB. 

I have disabled the HDMI port in the uenv.txt file and have confirmed it to be disabled.  The 6 control lines are connected to P8 pins 9-14, and the 16 data pins are connected to P8 pins 29-44.  3.3V power is taken from P9 and GND is taken from P8.  When I physically connect the display to these pins, the board does not boot.  I get an LED to come up but then it seems to pause and never boot.  The display requires a max current of 220mA which I know is close to the limit for the 3.3V supply, so I left the connections made, but removed the power to the LCD.  Same issue.  I checked for shorts on the connections...none that I could find.  There is NO buffer between the LCD and the uC as the boards have not been spun yet.  I am hooking it up using an FPC-to-wire converter cable.

Given my relative noobishness to the BBB hardware, I was hoping someone would have some fundamental oversight I am making here.

Thanks.

[Gerald Coley]

I suspect that your LCD design is interfering with the boot pins that are co-located with the LCD pins which is changing the boot order.

I suggest that you read the System Reference Manual for more information.

Gerald

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups "BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

--

Gerald

 

ger...@beagleboard.org

http://beagleboard.org/

http://circuitco.com/support/

[engka...@gmail.com]

I am having the same problem. After many testing, I found that the LCD pins 2,3 and 4 are being pulled down by my LCD if it is not powered. I confirmed by removing pins 2,3 and 4. The BBB booted while LCD is attached and unpowered. When I connect the LCD pin 2 (sysboot 2) It won't boot unless there is an SD card. This the same as the boot switch pulling the sysboot 2 to ground. So what I am thinking now is to have a mechanism that will disconnect this when the LCD is not powered. I don't know if adding level shifters or buffers with the same power rails connected to the LCD supply will work. What Else can I do?