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?
On Friday, April 17, 2015 at 1:28:33 AM UTC+8, Chris Handley wrote: > > 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. > -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/9386857a-89a5-4ef8-a16f-22ece463966f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
