Beagle Bone Black 4D Systems 4th Gen LCD, could not request pin 40

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Mecha Lec

Aug 27, 2019, 7:39:00 AM8/27/19
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I have a BBB Revision C, with 4DSystems LCD Cape. 

I am running 2net 4.1 Kernal ,

The screen shows "Android" and then this fades out. 

Looking at serial I have this error: 

[    3.353484] pinctrl-single 44e10800.pinmux: pin 44e108a0.0 already requested by panel; cannot claim for 0-0070
[    3.363651] pinctrl-single 44e10800.pinmux: pin-40 (0-0070) status -22
[    3.370239] pinctrl-single 44e10800.pinmux: could not request pin 40 (44e108a0.0) from group nxp_hdmi_bonelt_pins  on device pinctrl-single

I think this might be why it doesn't continue with the Kernal but I could be wrong. 

Referring to all available forum posts regarding this LCD I have tried many different options in uEnv.txt to disable HDMI, disable universal cape and alike but nothing seems to work. 
I am not sure what command options are actually relevant to this particular build. 

I have also read that the boot int eh EMMC can also affect the overlays which are being loaded by the image in the SD card. I have ensured I have loaded one of the latest flasher images from official beagle bone site. 
Running just this flasher image, the screen does display correctly so I know it is not a hardware related issue. 

I have also double checked the overlay that is being used and all the pins are correct and match the schematic of the display. 

I am a newbie to Beable Bone Black and Linux so this is incredibly difficult and have spent weeks now trying to overcome this hurdle. 
So any help would be greatly appreciated. 

I have attached the serial outputs from the problamatic SD image and also for my base EMMC. 

Hoping someone could provide some info to push me in the right direction. 


John Baker

Dec 14, 2019, 7:31:57 PM12/14/19
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I used a 4DSystems 4Dcapes for the BBB ( and added a real-ttime clock board and an analog I-O board that I designed and had fabbed at OSH Park. I used  Debian Linux OS and programmed it in Python along with using Matplotlib and Tkinter. It was a little tricky as there are conflicts with the pins. You should check the pinouts in the schematics for conflicts and also check for help from 4DSystems.
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